ALICE-USA. DRAFT - Research Management Plan

Transcription

1 ALICE-USA DRAFT - Research Management Plan December 9, 2006 Executive Overview The ALICE-USA Collaboration proposes to initiate a research program in relativistic heavy ion physics with the ALICE experiment at the Large Hadron Collider (LHC) at CERN, focusing on jet and heavy flavor probes of the produced nuclear medium. A separate MIE (major item of equipment) proposal to the DOE by the Collaboration to construct an electromagnetic calorimeter (EMCal) for installation in ALICE has recently passed the CD-1 stage. The ALICE- USA Collaboration presently consists of 12 DOE-supported research institutions: Creighton University, University of Houston, Kent State University, Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, Michigan State University, Oak Ridge National Laboratory, Purdue University, University of Tennessee, University of Texas at Austin, Wayne State University and Yale University. The primary research goal of ALICE-USA is to investigate QCD matter and measure its properties at high energy density in heavy ion collisions at the LHC. This document presents the ALICE-USA Research Management Plan to utilize the EMCal to significantly extend the available experimental information and overall knowledge about QCD at high energy density. The research will emphasize investigation of the medium modification of partonic energy loss ( jet quenching ) and the response of the medium to large depositions of jet energy. The measurements associated with the EMCal will focus on products of initial hard partonic scattering, such as high energy jets, photons and heavy flavors, and lower energy particles correlated with a trigger jet or quenched jet. The EMCal, combined with the excellent tracking and particle identification capabilities of ALICE, allows unique investigation of the behavior of high energy density QCD at the LHC. The research plan of ALICE-USA presents the overall physics goals of the Collaboration and a timeline of yearly research tasks and deliverables for the five-year period The plan is contingent upon a dedicated and robust software and computing effort to realize the full physics potential of data from the EMCal. The anticipated physics and papers to be derived from this research are outlined. The document also describes the organization of ALICE-USA and its communications and relationships (collaborative, management and financial) to ALICE and CERN. It describes how research personnel participate in the EMCal project, including responsibilities for calibrating, commissioning and data-taking with the EMCal in ALICE. Finally, a breakdown of the manpower required to accomplish this research program and the manpower available from the collaborating institutions is presented. 1

2 1. Overview 1.1 The ALICE Experiment The Large Hadron Collider (LHC) at the European Laboratory for Nuclear Research (CERN) in Geneva, Switzerland, will commence operation in The injection of the LHC with lead (Pb) nuclei in 2008 will introduce a new era in the investigation and understanding of high energy density QCD. ALICE (A Large Ion Collider Experiment) will be one of four large systems at the LHC, the other three being LHC-b, ATLAS and CMS. ALICE, the only dedicated heavy ion experiment, has more than 1000 scientists, engineers and technicians from 101 institutes in 29 countries working on it. ALICE will be prepared for data-taking with initial collisions of protons in 2007 and Pb nuclei in ALICE will be able to detect a broad range of particles encompassing many different observables at the LHC. The physics goals of ALICE are many-fold. ALICE expects to utilize products of hard scattering processes (jets, large transverse momentum particles and photons) as a probe to determine properties of the high temperature quark-gluon medium; charmonium and bottomonium production and suppression to establish the initial temperatures and the extent of deconfinement; particle spectra and yields in each event to determine the evolution and response of the medium to energy deposition; heavy flavor yields, spectra and tagged jets to extract expected differences in quark and gluon propagation; fluctuations in various measured quantities to extract characteristics of events; and will investigate the extent of gluon saturation and evidence of a possible color-glass condensate at the LHC. Measurements will be made not only with Pb+Pb, but also p+p, p+pb and lighter A+A systems for reference data and to understand fundamental underlying mechanisms. Building on studies that have been undertaken with experiments at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in New York, ALICE will be able to utilize the above-mentioned probes to study the system formed at LHC energies. Here the energy densities and lifetimes are expected to be twice larger than at RHIC, and hard probes approximately two orders of magnitude more abundant allowing more detailed studies of a system that is formed at much hotter temperatures. Likewise, rare probes such as bottom quark production will be two orders of magnitude more plentiful than at RHIC, allowing detailed investigations with heavy flavors. The ALICE experiment is being constructed in the large L3 magnet at CERN. Progressing outward from the interaction point, ALICE consists of 6 layers of silicon inner tracking detectors two barrels of silicon pixel detectors, two of silicon drift detectors and two of silicon microstrip detectors. Outside the silicon tracking is a large time projection chamber, transition radiation detector, time-of-flight, high resolution photon spectrometer, and ring imaging Cherenkov detectors for high momentum particle identification. A group of US and European institutions propose to construct an electromagnetic calorimeter (EMCal) for installation in ALICE. The EMCal will extend the capabilities of ALICE in the realm of hard probes and will enable a detailed tomographic study of the hot medium created at the LHC. It will enable ALICE to measure and trigger on large transverse momentum jets, photons, electrons and neutral pions in order to understand modifications of jet structures due to the dense medium. It will also facilitate photon-jet correlation measurements for in-depth studies of the modification of 2

3 fragmentation functions due to the medium. The EMCal makes ALICE, with its extensive momentum and identified particle analysis over a large acceptance, the unique facility to study the response of the medium to large energy deposition from parton energy loss. 1.2 The ALICE-USA Collaboration The purpose of the ALICE-USA Collaboration is to organize the US effort on ALICE to extract new physics, to determine and better understand the properties of dense QCD matter, and to investigate the quark-gluon plasma formed in collisions of heavy ions at the LHC, with an emphasis on hard probes through use of the EMCal. To accomplish this, members of the ALICE- USA Collaboration will focus initially on constructing, installing, and commissioning the EMCal in the ALICE experiment at CERN, and on developing the software and analysis tools necessary to accumulate and analyze EMCal data for physics. This will ensure that the EMCal Project is completed successfully, thus promising a rich program of exciting new physics from collisions of heavy ions at the LHC. The new physics brought to ALICE by the EMCal can be divided into two basic categories of investigation, each emphasizing the jet physics capabilities made available by addition of the EMCal in Pb + Pb collisions: medium modification to partonic energy loss and response of the medium to the large energy deposition from partons. It will also be important to acquire and understand reference data in p + p, p + A and light A + A collisions. While the membership in the ALICE-USA Collaboration is technically not exclusive to DOEsupported institutions, the general purpose of the ALICE-USA Collaboration is to organize the US research efforts within the ALICE experimental program at the LHC with a particular interest in and focus on the DOE-supported institutions. This includes the coordination of proposals for construction of major experimental equipment starting with the large area Electromagnetic Calorimeter (EMCal) for ALICE, as well as for non-detector components such as computer processor farms, controls systems, and related software. The ultimate goal of the ALICE-USA Collaboration is to focus and leverage the efforts of the US institutions working on ALICE on the highest priority scientific objectives and to maximize US involvement and impact in the LHC heavy-ion program. The ALICE-USA Collaboration will also function as the global organizational interface in representing the combined interests of the DOE-supported member institutions to the DOE itself and within the overall ALICE Collaboration governance infrastructure in cases where such a combined representation is appropriate and/or required. The ALICE-USA Collaboration is proposing to fabricate a large electromagnetic calorimeter (EMCal) as a Major Item of Equipment (MIE) for the Office of Nuclear Physics of the Department of Energy (DOE). The EMCal will become an integral component of the ALICE experiment at the LHC at a Critical Decision One (CD-1) approximate Total Project Cost (TPC) range of $13 to $16 million to the DOE. The primary goal of the ALICE-USA Collaboration at this time is to construct, install and operate the EMCal in ALICE and to extract the physics associated with the EMCal. The ALICE-USA Collaboration is governed by its Bylaws adopted June 20, 2006, which are included as Appendix A of this document. The governing bylaws, the management structure and the operational procedures of ALICE-USA are discussed below. 3

4 1.3 The ALICE EMCal Project The EMCal will allow ALICE to explore fundamental questions into the nature of the Quark- Gluon Plasma (QGP) that cannot be examined with any other experimental facility worldwide. This research proposed by the ALICE experiment including the EMCal will complement and extend ongoing investigations at the Relativistic Heavy Ion Collider (RHIC) currently the DOE s world-wide flagship facility of the field. The observation of jet quenching and its sensitivity to properties of QCD matter are important discoveries at RHIC. The further study of jets in dense matter will play a central a role in the LHC heavy ion program. It is crucial that the LHC experiments have the capabilities both to exploit the large kinematic range of jets made available by the machine and to measure jet structure and its medium-induced modification in detail. This dictates the need for efficient triggering, robust tracking and detailed particle identification capabilities to low p T, since much of the physics related to the response of the medium is carried by soft fragments even for the highest energy jets. Robust tests of the physics underlying energy loss will be made using quark jets tagged by heavy flavor decay, light hadron-led gluon jets, and γ+jet coincidences. The interaction of the jet with the medium and the response of the medium will be studied at low and intermediate p T for a broad range of jet kinematics. The proposed ALICE Electromagnetic Calorimeter (EMCal) adds significant new physics scope to the ALICE experiment, in particular for the study of medium induced modification to jets as a probe of dense matter ( jet quenching ). The EMCal in ALICE enables the most extensive exploration possible thus far of jet fragmentation in heavy ion collisions. The EMCal will provide 1) an efficient unbiased high E T jet trigger over a broad jet energy range in topologically complex heavy ion collisions, and efficient triggers for high p T photons and electrons; 2) detailed exploration of the medium-induced modification of jet fragmentation over a broad kinematic range, from the hardest jet fragments of high E T jets to very soft fragments, when coupled with the excellent tracking and particle identification capabilities of ALICE; 3) direct photon detection, enabling determination of the initial parton-level scattering energy prior to medium-induced modification and fragmentation of the recoil jet opposite the photon; and 4) hadron rejection for efficient measurement of high p T electrons, enabling studies of heavy quark jets. The physics capabilities of the EMCal are described in the ALICE EMCal Technical Proposal to CERN (CERN-LHCC ) and the ALICE EMCal Conceptual Design Report to the US DoE (EMCal.3.1.v1). The latter Report is included as Appendix B to this document. The essential design parameters for the physics performance of the EMCal are its total coverage and tower granularity. The performance outlined in the EMCal Conceptual Design Report indicates a broad range of capabilities. The overall acceptance of the EMCal is sufficiently large to allow a competitive jet physics program. The EMCal is targeted at detailed studies of jet fragmentation in heavy ion and p + p collisions. It is not intended to compete with ATLAS and CMS in their areas of strength for Higgs and super-symmetry searches. It is our view that the EMCal makes ALICE the premier experimental facility at the LHC for studying the full spectrum of jet physics in heavy ion collisions. In October 2006 the Large Hadron Collider Committee (LHCC) approved the EMCal for installation as an integral part of the ALICE research program. 4

5 Over the past several years, pre-conceptual R&D has been carried out and the technology identified to construct a large electromagnetic calorimeter capable of addressing the ALICE Collaboration s physics requirements. R&D will continue into FY 2007, with the project MIE activity expected to start sometime in FY 2007 and completed in FY The project has received Critical Decision Zero (CD-0) and critical decision one (CD-1 ) approval and is preparing for CD-2/3 in the third quarter of FY07. An addendum to the ALICE Technical Proposal describing the physics reach of ALICE plus the EMCal has been approved by the LHCC and as part of our CD-1 documentation, an EMCal Technical Design Report has been accepted by the DOE. A Project Execution Plan (PEP) that describes the coordination of efforts of the project team, including the procedures used by the EMCal contractor project manager (CPM) for the project to be completed on time and within budget has also been accepted by the DOE. The PEP defines the project scope consistent with the funding profile, identifies the roles and responsibilities of contributors, and presents the work breakdown structure (WBS) and schedule for the project. The PEP (EMCal.4.1.v1) is included as Appendix C of this document. 1.4 Overview of ALICE-USA Research Plan The success of the research of the ALICE-USA Collaboration is intimately linked to the successful construction, installation and operation of the US DOE-funded EMCal in ALICE. ALICE-USA Collaboration members have leading responsibilities in the ALICE EMCal Project. The ALICE-USA Collaboration is responsible for providing the infrastructure in the US that is necessary for 1) establishing and maintaining optimal performance of the EMCal, 2) data-taking with the EMCal, and 3) extraction of the physics associated with the EMCal in ALICE. The purpose of this Research Management Plan is to specify how these responsibilities will be carried out by ALICE-USA and its member institutions. The remainder of this document will be organized as follows. The scientific goals of ALICE-USA, the research program of ALICE-USA and how it will be carried out, ALICE-USA participation in the EMCal project, and the organizational structures of ALICE-USA and ALICE will be presented along with their interrelationship. 2. Scientific Goals of ALICE-USA The primary physics goal of ALICE-USA is to investigate and better understand QCD matter. We will measure properties of the high density QCD matter created in collisions of relativistic heavy ions at the LHC via the medium modification of partonic energy loss ( jet quenching ) and the response of the medium to large depositions of jet energy. Measurements will focus on products of initial hard partonic scattering, such as high energy jets, photons and heavy flavors, and lower energy particles correlated with a trigger jet or quenched jet. The EMCal, combined with the excellent tracking and particle identification capabilities of ALICE, allows a unique investigation of the behavior of high energy density QCD. This will be the focus of the ALICE- USA Research Management Plan. The issues of the parton energy loss mechanism and the response of the medium to the deposited energy are related but distinct, and we elaborate on each below. 5

6 2.1 Partonic Energy Loss Parton energy loss in colored matter is an interesting and long-standing problem in QCD. 1 It has recently gained prominence due to its use as a probe of the QCD matter produced in relativistic heavy ion collisions at RHIC and the LHC. In general, the most precise predictions and experimental tests of QCD address the Q 2 evolution of observables (e.g. F 2 (x,q 2 )). The LHC provides an enormous increase relative to RHIC in the kinematic reach for perturbative QCD probes, making the study of the Q 2 evolution of jet quenching possible over a logarithmically large energy range. Such measurements are expected to provide a deep understanding of the physics of partonic interactions in dense QCD matter. 2 The ALICE EMCal enables significant measurements at jet energies beyond 200 GeV in Pb+Pb collisions, 3 allowing detailed investigation of the Q 2 evolution of jet quenching. The large yield of high transverse energy (E T ) jets enables full jet reconstruction over the heavy-ion background for E T > 75 GeV, giving a comprehensive study of jet quenching without the geometric and fragmentation biases present in leading particle studies at RHIC. A wide array of jet structure observables that are sensitive to partonic energy loss will be measured with the EMCal in ALICE. The longitudinal fragmentation function is expected to be softened as at RHIC, leading to marked suppression of hadrons carrying a large momentum fraction z (z = p hadron /E jet ) of the jet, in coincidence with a strong enhancement in the yield of soft, low z hadrons. Jet heating resulting from the energy loss can be measured via the hadron momentum distributions perpendicular to the jet axis. Studies of jet shapes and energy clustering within the jet may indicate the fate of hard radiation in the dense medium. 4 The magnitude of energy loss in the medium is dependent upon the velocity and color charge of the probe. 5 While the jets produced in heavy ion collisions at the LHC are dominantly gluon jets, rare heavy quark jets can be distinguished and tagged by the presence of a high p T electron. For moderate jet energies on the order of the (heavy) quark mass, the dead cone effect 6 suppresses forward radiation, leading to a mass dependence of the energy loss in pqcd. 5 For sufficiently high energy heavy quark jets, the dead cone effect does not play a role in the energy loss and the electron tag serves simply to distinguish quark jets from gluon jets. In pqcd the energy loss of a high energy quark is 4/9 that of a gluon, which should result in experimentally observable effects. The EMCal extends the ALICE capabilities for heavy quark jet measurements significantly, enabling efficient electron triggering and identification well beyond 20 GeV (~50 GeV jets and beyond). 1 M. Gyulassy and M. Plumer, Phys. Lett. B 243 (1990) 432; X. N. Wang and M. Gyulassy, Phys. Rev. Lett. 68 (1992) 1480; R. Baier, Y. L. Dokshitzer, A. H. Mueller, S. Peigne and D. Schiff, Nucl. Phys. B 484 (1997) N Borghini and U. Wiedemann, hep-ph/ ; A. D. Polosa and C. Salgado, hep-ph/ ALICE EMCal Technical Proposal to CERN (CERN-LHCC ); ALICE EMCal Conceptual Design Report to the US DoE (EMCal.3.1.v1). 4 C.A. Salgado and U.A. Wiedemann, Phys. Rev. Lett. 93 (2004) ; I. Vitev, hep-ph/ N. Armesto, A. Dainese, C. Salgado and U. Wiedemann, Phys. Rev. D71 (2005) Y. L. Dokshitzer, V. A. Khoze and S. I. Troian, J. Phys. G 17 (1991); Yu.L. Dokshitzer and D.E. Kharzeev, Phys. Lett. B519 (2001)

7 An alternative, non-perturbative calculation of jet quenching uses the AdS/CFT correspondence between strongly coupled QCD and dual theories of weakly-coupled gravity. 7 Recent jet quenching calculations for the N c = 4 super-symmetric Yang-Mills cousin of hot QCD also find a mass dependence for quark energy loss. 8 However, the dependence of energy loss on the color density of the medium exhibits different scaling behavior in such theories (q-hat ~ N c ) than in pqcd (q-hat ~ N 2 c ). 9 While testable predictions from string theory for heavy ion collisions have not yet emerged, this is a very active and promising area of theoretical investigation. Establishing an experimental connection between these areas of physics would have tremendous impact. The electron triggering and measurement capabilities of the EMCal also enable the measurement of W+ and W- in the ALICE central detectors, complementing similar measurements in the muon arm. Electroweak gauge bosons are hard probes par excellence but do not carry color charge and hence do not interact with the medium, thereby providing an important normalization for jet quenching measurements. Inclusive measurements of direct photons provide another essential cross-check on measurements of jet quenching, as demonstrated by PHENIX at RHIC. Such measurements will likewise be important at the LHC, though more difficult due to a substantially lower γ/π ratio in the accessible region. Direct photon measurements enable the crucial γ + jet coincidence measurement, in which the photon provides the energy calibration for the recoiling jet. 10 Gluon shadowing will be determined through measurements of γ + jet in p + p, p + A and A + A collisions. Measurements of γ + jet correlations are expected to provide the most precise information on medium-induced modification of the fragmentation function. Variation of geometrical constraints, in particular through correlation with the reaction plane in non-central collisions, will be especially sensitive to medium effects, though such measurements are statistically challenging. To better understand the fragmentation process and its modification by the medium, identified particle fragmentation functions will be measured in p + p and heavy-ion reactions. Baryonmeson and flavor differences in fragmentation 11 will allow further investigation of the partonic energy loss mechanism and may shed light on the relevant degrees of freedom in the hadronization process (e.g. constituent quarks 12, di-quarks 13 or colored states 14 ) and the medium itself. Observable properties of hadronic resonances, such as mass, width, and branching ratio as a function of the fractional momentum z, inside and outside the jet, may be sensitive to properties of the hot medium, possibly chirality 15. Investigation of the space-time evolution of 7 J. M. Maldacena, Adv. Theor. Math. Phys. 2, 231(1998). 8 e.g. S. Gubser, hep-th/ ; C. P. Herzog, hep-th/ H. Liu, K. Rajagopal and U. Wiedemann, hep-ph/ X.N. Wang, Z. Huang, and I. Sarcevic, Phys. Rev. Lett. 77 (1996) R. Hwa and C.B. Yang, PRC 73 (2006) A. Peshier, W. Cassing, PRL 94 (2005) P.Eden and G.Gustafson, Z.Phys. C75 (1997) E. Shuryak and I.Zahed, PRD 70 (2004) G. David, R.Rapp and Z.Xu, nucl-ex/ and R.Rapp, nucl-th/

8 jet fragmentation will be undertaken through measurements of hadronic resonances 16 and HBT relative to the jet axis, where comparison of these observables in the same events may exhibit sensitivity to the hadron formation time 17 and lifetime of the system Study of the QCD Medium and its Response to Partonic Energy Loss The ALICE EMCal facilitates investigation of properties of the QCD medium, such as transport coefficients (diffusion, viscosity, speed of sound), through the response of the medium to the energy lost by the traversing partons. Theoretical calculations suggest that dissipation of the jet energy may occur via Mach shock waves, 19 color wakes 20 or Cherenkov-like gluon radiation. 21 Multiparticle correlation measurements relative to the jet direction and as a function of collision geometry and jet energy will provide information on the energy dissipation mechanism and may distinguish these effects. 22 The extensive particle identification capabilities of ALICE allow studies of a wide array of identified hadrons and hadronic resonances, both inside and outside of jets. RHIC has shown that hadron distributions in heavy ion collisions are strongly modified at intermediate p T. This is commonly attributed to an interplay between bulk matter and the fragmentation of hard scattered partons. Observation of the scaling in this region of elliptic flow (v 2 ) with constituent quark number suggests that the degrees of freedom at freezeout are partonic rather than hadronic 23. The inclusive distributions and correlations at intermediate p T have been described successfully at RHIC by phenomenological recombination models 24. Such models suggest a hadronization mechanism which is different from a simple string fragmentation process. It requires the existence of a thermalized parton phase and the hadronization of baryons and mesons through parton coalescence. The existence of such a hadronization process in the dense partonic medium may be distinguished from string fragmentation through further measurements of spectra 25 and correlations 26 of identified particles out to large p T, within and outside jet cones and as a function of jet energy and collision geometry. The EMCal jet triggering and tagging capabilities play an important role for measurements investigating the response of the medium. They select on events with large particle yields in the momentum range (5-15 GeV/c) of interest due to a strong enhancement in the yield of soft, low 16 J.Adams et al. (STAR), PRL 97 (2006) K.Gallmeister and T.Falter, PLB 630 (2005) M.Lisa et al., Ann.Rev.Nucl.Part.Sci. 55 (2005) J. Cassaldery-Solana, E.V. Shuryak and D. Teaney, J. Phys. Conf. Ser. 27 (2005) 22; H. Stoecker, Nucl. Phys. A 750 (2005) J. Ruppert and B. Muller, Phys. Lett. B 618 (2005) V. Koch, A. Majumder and X.N. Wang, Phys. Rev. Lett. 96 (2006) see c.f., S.S. Adler et al, Phys. Rev. Lett. 97 (2006) S.A.Voloshin, J.Phys.Conf.Ser. 9 (2005) R.J. Fries et al., PRL 90 (2003) and PRC 68 (2003) R. Hwa and C.B. Yang, PRL 97 (2006) R. Hwa and C.B. Yang, nucl-th/

9 z hadrons in quenched jets. The flow and correlation characteristics of these intermediate pt hadrons can be interpreted within the recombination and fragmentation hadronization models, which not only determine the hadronization mechanism but also the level of thermalization of the partonic medium at hadronization. The EMCal determination of the jet energy and the jet axis allows measurement of identified hadrons and hadronic resonances as a function of their fractional momentum z and azimuthal distribution. In addition, the EMCal identifies high momentum leptons and photons, necessary for the reconstruction of hadronic resonances and heavy quark states. The EMCal will enhance ALICE s capabilities to measure J/ψ at high p T, which is potentially of interest to test the velocity scaling of the heavy quark correlation length predicted in the AdS/CFT approach Physics Strategy The great success of the RHIC experiments in studying complex heavy ion collisions is due in large part to a strategy of systematic comparison between collision systems. This approach relies on comparing to the elementary production rates as measured in p + p collisions and provides essential cross-checks and calibrations for theoretical approaches that are necessary to extract the underlying physics. The same systematic approach will be taken at the LHC. Measurements will be made in p + p, p + Pb and Pb + Pb with identical detection systems allowing comparable kinematic coverage and statistical precision for hard probes. There are, however, additional complexities at the LHC. Different systems will be measured at different collision energies, and the evolution of observables will need to take into account the collision energy when comparing data-sets. In particular, Pb + Pb will collide at s NN = 5.5 TeV, whereas most of the p + p operation will take place at s = 14 TeV. The enormous kinematic reach for hard probes at the LHC presents an additional challenge. Jet quenching will necessarily be measured differently for 20 GeV jets (e.g. few-particle correlations as at RHIC) than for 200 GeV jets (e.g. full jet reconstruction). The EMCal is key to the measurements proposed by ALICE-USA. When coupled with measurements of the same events in other ALICE detectors, the jet measurements and triggering provided by the EMCal constitute a unique program of measurements investigating response of the medium to jet energy deposition. Control of systematic effects, and meaningful comparison of various collision systems and kinematic ranges, will require integration of the measurements from other ALICE detector systems, such as the TPC, the Inner Tracking System, and the PHOS, in order to extract the unique jet-correlation physics the EMCal brings to ALICE. Many of the measurements in the jet program require the identification and correlation of particles inside and outside the jet cone, in order to determine medium modifications to fragmentation and properties of the QCD medium. The significantly enhanced physics reach that is accomplished with large EMCal event samples at high jet energies will allow correlations with particles in ALICE detectors that have significant particle identification capabilities, such as the 27 H. Liu, K. Rajagopal and U. Wiedemann, hep-ph/

10 TPC, TRD and PHOS. A comprehensive program also using information from these detectors will lead to the physics goals described in the previous section. The ALICE-USA collaboration will need to develop an understanding of the performance and data from these other detectors prior to installation and data-taking with the EMCal in order to undertake correlation measurements with triggered and tagged EMCal data. 3. Research Program of ALICE-USA The primary responsibilities of the ALICE-USA collaboration are to construct, install, commission and operate the US DOE-funded EMCal in ALICE; to develop and implement the software and analysis tools necessary to accumulate and analyze ALICE EMCal data; to develop the physics capabilities of the ALICE EMCal, and extract the unique physics associated with the EMCal in ALICE. The research plan for ALICE-USA, covering all tasks that are not a formal part of the EMCal Project, can be divided into four general areas necessary for effective utilization of the EMCal in ALICE. These are: a) EMCal detector support and operations, b) online software and trigger, c) offline software for simulations and analysis of data for extraction of physics, and d) Offline Computing. A description of the work tasks and deliverables in each of these four areas is presented below, followed by a chronological presentation of the deliverables. A summary of the number of FTEs per year required for successful completion in each of these areas and the manpower committed to accomplish these from institutions in ALICE-USA are presented in Appendix F. 3a. Description of Tasks and Deliverables - EMCal Detector Support and Operations The ALICE-USA collaboration supports the detector project via the following broad tasks: (1) Participation in test beam setup and data accumulation. (2) The development and application of scientific tools essential to understanding detector performance and limitations through simulations and test beam data analysis. (3) Establishment of the EMCal pre-calibration via cosmic ray measurements with completed super modules and the transfer of the pre-calibration to the LED system. (4) Development of calibration protocols to be applied in ALICE in simulations and their validation, to the extent possible, through test beam analysis and participation in the first round of PHOS calibrations. 10

11 (5) Participation in EMCal installation activities to provide QC/QA measurements using the LED system and/or cosmic rays immediately before and after super module installation. This is followed by a systematic detector-commissioning program. (6) Development of an EMCal slow controls system, maintenance of the associated software and provision of annual updates to the system as the number of modules increases (7) EMCal operation and monitoring during ALICE running. Each of these tasks required to accomplish the associated deliverables is discussed in more detail in the following. (1) Participation in the EMCal test beam The project plan calls for two independent test beam measurements with prototype EMCal modules. The first of these was performed in 2005 at the Fermi Lab Meson Test Facility using an array of 8x8 = 64 towers (4x4 modules) of a preliminary design. Data was digitized with near-final design front-end electronics and read out through a local copy of the ALICE DAQ system. A total of 16 ALICE-USA collaborators from 7 institutions participated in the month long run at Fermi Lab. In addition, 2 ALICE-EMCal collaborators from Frascati also participated. Following the data taking, these institutions actively participated in the analysis, which is nearing completion at this point. Based on these first test beam results, a final EMCal module design has been completed and first copies of the final readout electronics are available. A second test beam is now planned with the first set of production modules. These measurements will be made either at Fermi Lab or at the CERN PS depending on the exact scheduling. This second set of test beam measurements will be considerably more extensive than those of the first test beam. We expect they will provide an important database of module characteristics that is needed for ongoing detector performance simulations. We foresee, therefore, the need for an expanded collaboration involvement in both the setup and run phase. (2) Analysis tools The test beam measurements to be conducted in 2007 provide the first opportunity to study the performance of the final design modules and readout electronics with real data. To be most effective, this requires the development of a GEANT model of the test beam geometry, including trigger and tracking detectors, which can be used to simulate and then validate shower shape parameters, cluster finding/reconstruction, e/h discrimination, etc. with real data. These simulations and their calibration with test beam data can then be used to provide a realistic foundation for the development of EMCal offline analysis tools and thus calibrate the physics performance simulations conducted in the ALICE geometry for Pb+Pb and p+p data. (3) EMCal pre-calibration based on cosmic ray muons The overall EMCal calibration plan assumes that an absolute cosmic ray pre-calibration is made for each tower to a level of better than 10% systematic uncertainty in the energy calibration for each tower prior to installation in ALICE. Measurements with test beam tagged muons show that this level of calibration should be easily achieved with cosmic rays. At the point of final super module assembly and integration, members of the ALICE-USA collaboration will conduct 11

12 cosmic ray measurements and transfer this absolute calibration to the LED system for each tower in the calorimeter. This calibration along with absolute gain curves for the APDs will be used to set the starting conditions for the EMCal data acquisition and trigger. (4) EMCal calibration The final EMCal energy calibration will utilize a variety of reference data including minimum ionizing, high P T hadrons, tracked conversion-electron momentum measurements in the TPC and inner tracker and the reconstructed masses of π ο, J/ψ, ϒ, and Ζ ο versus p T. The collaboration is responsible for the preparation of the necessary software tools and for performing the initial online and then off-line calibration as super modules are installed. The collaboration will be responsible for updating the calibration each ALICE running year. Prior to the initial super module calibration, many of the software tools can be validated using PHOS data. (5) Installation/commissioning The ALICE-USA collaboration members will participate in the installation of super modules. As each super module is installed and before installation tooling is removed, the collaboration will have its first opportunity to examine the super module status using ALICE DAQ and the EMCal on-line system. This time window provides the last opportunity to easily make minor corrections to the super module, repair dead channels, etc. Once the super module is in its final position and fully integrated into the DAQ, trigger, and slow controls, the collaboration takes over the task of detector commissioning. (6) EMCal slow controls A dedicated online operating system to required to provide control functions for the EMCal both in the test beam and once installed in ALICE. This system allows control of detector parameters such as photo sensor HV and trigger and digitizer parameters. In addition, the system provides the link for software download and initialization to front end electronics and also provides the main tool to monitor detector status. The slow controls is developed and prototyped for the test beam in 2007 and implemented in ALICE in In subsequent years, the system is updated and commissioned along with new modules as they are installed. Controls systems software maintenance is an ongoing task throughout EMCal operation. (7) Detector operations The LHC will be in operational mode for over 9 months per year, which is estimated to yield ~140 days for physics operation. Most of this is p+p running at 14 TeV but in the early years, at least, ALICE will participate fully in p+p running for reference data as well as for the novel p+p physics at 14 TeV for which ALICE is uniquely suited. ALICE-USA collaboration members will be responsible for EMCal set up, operation and monitoring during all ALICE running. In addition, some lower level of ALICE-USA staffing will be required during the estimated 1 to 1.5 months of annual accelerator setup time. Approximately 500 to 600 shifts must be manned in a nominal ALICE year in which there is full participation in p+p running. Beyond the first few years of LHC running, ALICE may choose to reduce its participation in p+p running for physics. However, it is envisioned that substantial p+p running will be used each year to prepare the full ALICE detector, including the EMCal, for an efficient start up in Pb+Pb running. Thus, if we assume 2 staff members per shift (this is a minimum for operations and 12

13 monitoring) are required then detector operations accounts for approximately 4 to 5 FTEs per year in the early years (beginning in 2008) reducing to perhaps 3 to 4 FTEs in later years. 3b. Description of tasks and deliverables - Trigger There are two classes of Level 0/1 trigger for the EMCal: gamma/electron: utilizes existing PHOS-type capabilities for fast triggering for small clusters (4x4 tower sums) jet trigger: unique to EMCal, technical implementation under development. Sums large areas (typically δηxδφ~0.2x0.2 or larger) In addition, the EMCal will provide input to the ALICE High Level Trigger (HLT). L0/1 Quantitative study of both gamma/electron and jet trigger requires flexible and detailed mechanisms to be set up within the ALICE simulations framework. The framework must include accurate modeling of trigger architectures, together with mechanisms to embed simulated signal in background events. The physics performance of the L0 and L1 gamma/electron trigger will be assessed using this framework. Level 0 is relevant only for small, high rate collision systems such as p+p and p+pb. The Level 1 performance will be quantified for the full range of collision systems (including centrality dependence for Pb+Pb), for representative observables including high p T π 0, direct photons, electrons from heavy quark decay, and electrons from quarkonium decays. Physics simulations will indicate the required rejection factors and quantify efficiency and thresholding characteristics in p+p, peripheral Pb+Pb and central Pb+Pb. A Requirements Document will summarize these studies. A targeted effort will also be made to design and implement triggers for the Ultra-peripheral Collisions program in ALICE. This program is not yet well developed and work in this direction has not yet begun. Jet trigger: The jet trigger is an upgrade to the PHOS electronics, designed to exploit the large coverage of the EMCal to extend ALICE jet measurements to very high E T for the full range of LHC collision systems (p+p, p+pb, Pb+Pb). Detailed simulations of jet trigger response, required to optimize the jet trigger design, will be carried out in collaboration with the EMCal trigger electronics team (CERN, Grenoble, ORNL). Physicists from ALICE-USA will participate in trigger algorithm development, which includes some FPGA programming. A Requirements Document is being developed to summarize these studies. Physicists from ALICE-USA will collaborate with electronics, online, DAQ and trigger teams to implement, commission and test jet trigger prototypes and establish the final design. 13

14 Software: On-line calibration, monitoring and QA procedures will be developed for all classes of L0/1 trigger. Offline software development is needed to measure trigger efficiency via comparison to minimum bias data. High Level Trigger (HLT) Physicists in ALICE-USA will work with the ALICE High Level Trigger (HLT) group to modify and implement offline algorithms for jet finding, electron PID, and other EMCal-related functionality in the HLT framework. EMCal-specific HLT hardware/connectivity and other Online issues will also need to be addressed. Detailed simulations are needed to assess HLT performance for representative observables where the HLT plays a role (jets, electrons) in p+p, p+pb and Pb+Pb collisions. This will include realistic modeling of L1 performance together with estimates of LHC performance, ALICE datataking configurations, and HLT performance. Comparison will be made to measurements carried out without the EMCal in the HLT, to quantify and document the physics gains due specifically to HLT processing. This provides essential input to the global ALICE decisions for data taking strategies. EMCal Trigger Performance A separate and distinct task is the assessment of the overall performance of the EMCal triggering system. This requires simulations and calculations to estimate the recorded datasets for representative observables (γ, π 0, electrons, jets) in various collision systems (Pb+Pb, p+p@14 TeV, p+p@5.5 TeV, p+pb, light ions), taking into account expected LHC performance and ALICE data-taking configurations. Comparison of EMCal-triggered measurements to other ALICE data-taking approaches for the same or similar physics observables will quantify the gains due to the EMCal trigger. Such studies will identify key issues for optimization of datataking strategies, including requirements on minimum-bias data-taking for trigger calibrations. Formal documentation of the EMCal trigger performance will provide essential input to ALICEwide discussions about data-taking strategies. 3c. Description of Tasks and Deliverables - Offline Software for Simulations and Analysis of Data Responsibility to develop and maintain the offline software for simulation, reconstruction, calibration and analysis of EMCal data lies with ALICE-USA. A core team of developers with a coordinator to act as liaison to ALICE offline computing will manage this aspect of the project, with additional manpower coming from collaboration members who expect to analyze data for physics results. A dedicated discussion list and periodic teleconferences will be used to manage this work. 14

15 The initial years of the involvement of ALICE-USA in ALICE will be used to develop simulation software for the EMCal as well as the analysis code for EMCal specific physics measurements. Initially, the highest priority task is to develop computer software code for detector response that allows determination of detector efficiencies for simulated signals embedded in real events. The simulation code for such tasks will establish efficiencies for a variety of topics including electron/hadron discrimination, photon and neutral pion reconstruction, leptonic decays of heavy flavor, vector meson and resonance reconstruction, and jet energy reconstruction. These tasks must be completed by 2009, when EMCal components are first used in ALICE. The second priority is to execute detector performance simulations for specific calorimeter-based analyses in p+p and Pb+Pb collisions. These simulations, to determine the performance of the EMCal, rely partially on analysis of p+p and Pb+Pb data prior to installation of the EMCal. These pre-emcal analyses will establish the accuracy and efficiency for tracking to clusters in the EMCal, localization of secondary vertices for identifying heavy flavor decays, ability to distinguish specific secondary decay channels, and the reconstruction of hadronic resonance decay channels to compare to leptonic decay channels measured with the EMCal. Furthermore, minimum bias hadronic reference spectra and correlations must be analyzed for comparison to EMCal triggered and tagged events. The third priority will be to develop a full offline reconstruction chain within the ALICE analysis framework. The chain will include jet-finding algorithms, full jet reconstruction, jet triggering conditions for heavy flavor jets, photon jets, and hadronic di-jets. Particle identification procedures based on EMCal signals for neutral pions, photons, hadronic resonance and vector meson decays, as well as heavy flavor particles will be developed and tested with partial EMCal coverage. Once data-taking commences, specific physics driven analysis chains will need to be implemented to achieve the physics goals outlined in the research plan and in the chronological breakdown that follows. These physics topics include: - parton energy loss measurements as a function of jet flavor, jet energy and angular distribution relative to the collision geometry, and system size - high transverse momentum spectra of identified and non-identified hadrons, hadronic resonances, and vector mesons, as well as correlations as a function of jet flavor, energy, angular distribution with respect to the collision geometry, and system size - vector meson (J/ψ and Ψ) yields and spectra in the EMCal A summary of the current status for major components of the offline software and discussion/projections for further effort and improvements are presented below. Geometry A geometrical description of the detector for simulation with the ALICE Monte Carlo simulation suite has been developed for a preliminary detector design and is in use for simulation studies. Modifications will be required once the final detector design parameters have been established. 15

16 Data Structures EMCal data structures for raw, reconstructed and event summary data (ESD) have been defined and implemented with a preliminary mapping of detector channels to offline data format. As the design is finalized and the electronics are laid out, these structures and the accessor methods to fill and read back these structures will need to be modified. Simulation Simple creation of detector signals (digits) from GEANT simulated energy deposition (hits) has been implemented. The APD and FEE response parameters, along with electronic noise estimates must be applied to correctly transform simulated hits to detector digits once the electronics have been finalized. Algorithms to convert simulated digits to raw data format for propagating simulated data through the full reconstruction has been implemented, but needs to be evaluated and revised. Once the 2007 testbeam analysis is completed, reconstruction of simulated data should be compared to the testbeam results and simulations tuned to match the testbeam data. Alignment The number and format of alignment constants for accurate positioning of EMCal detector elements within ALICE have been established. Algorithms to translate and apply the survey data are needed. Calibrations Several possible offline calibration strategies were outlined in Section 3a. The software and database structures to generate and apply constants stored in the database must be designed and implemented. Trigger The performance of the triggers outlined in section 3b. should be evaluated and verified with simulations and real data in offline. The development of software for this task has begun, but requires further effort to provide feedback and efficiency estimates for the envisioned triggers. Reconstruction Initial algorithms for cluster finding and reconstruction using a nearest neighbor search have been implemented. Reconstructed clusters are stored in the ALICE Event Summary Data (ESD) format for offline analysis. Preliminary cluster and charged track matching software has been developed but requires tuning and evaluation. Particle Identification Cluster shape fitting for particle identification needs to be implemented and optimized. A preliminary gamma/hadron discrimination algorithm based on cluster size also exists but needs to be studied and refined. Electron identification using track matching is a high priority topic. A preliminary invariant mass algorithm for pi0 identification has been started, but cut optimization for different pi0 opening angles/transverse momentum regions requires further study. Analysis Analysis software for most specific physics topics is either in a very preliminary stage or has not 16

17 yet been undertaken. However, a cone jetfinder algorithm with background subtraction methods for heavy ion collisions was written and detailed studies of a preliminary EMCal design + fast ALICE tracking were performed and published in the Journal of Physics G. New efforts to implement a jet-splitting correction for the cone jetfinder and evaluation of the EMCal performance for investigating medium modifications to jet fragmentation functions have begun. Evaluation of the performance of FastJet, a k T jetfinder based on geometric nearest neighbor clustering for large multiplicity environments, using the EMCAL clusters and ALICE tracking is underway. 3d. Description of Tasks and Deliverables - Offline Computing ALICE-USA is responsible for all offline software associated with the EMCal. This includes software for simulations, data reconstruction, triggering, calibrations and analysis. The above research plan requires ALICE-USA to prepare aggressively for a full-scale analysis significantly prior to the data acquisition starting in FY09. The milestones for offline software are designated in Appendix D. ALICE-USA is required to provide computing resources in proportion to the Ph.D. fractional representation on the ALICE author list, and will assume responsibility for all offline tasks that pertain to the raw data format, calibration, and simulation of the EMCal detector. Details for these tasks are provided in the ALICE-USA computing plan, attached as Appendix D. Operations and Coordination with Facilities: We are expecting to run the offline computing tasks at a total of four facilities: the National Energy Research Scientific Computing Center (NERSC), the Ohio State Supercomputing Center (OSC), the Texas Learning Center (TLC), and Livermore Computing (LC). ALICE offline software has been installed at each site, and is currently running on two sites, NERSC and OSC, as part of the ALICE 2006 Physics Data Challenge. Each site will have a local facility coordinator who will be responsible for insuring that the software is current and the facility is operational. They will be the primary liaison from ALICE and ALICE-USA to the facility operations staff. Grid tool development and implementation ALICE software relies on Grid middleware for coordination across the collaboration s international computing resources. The jobs are currently handled by installing an ALICE Environment (AliEn) VO-box to handle job submission through the local job control software on each facility. We have proposed replacing this with an interface to the Open Science Grid (OSG) software that is under development through the combined support of SciDAC and the NSF and to enhance data management using OSG tools. A proposal to the NSF Physics at the Information Frontier (PIF) to fund this effort in collaboration with the OSG development group is currently pending. 17

18 3e. Deliverables by Year 2007 EMCal Detector Support and Operations Develop cluster finder and reconstruction tools Develop e/h discrimination tools Complete 2006 test beam analysis of shower shapes, etc. Participate in 2007 test beam and test/improve cluster tools test/improve e/h tools validate performance relative to requirements initial development and testing of EMCal slow controls EMCal installation test Trigger Develop software framework for detailed trigger simulation studies Carry out simulations to study EMCal trigger performance at L0, L1 Carry out simulations to determine requirements of Jet Trigger First studies of triggers for Ultra-peripheral collisions Development of software tools for Online trigger calibration, monitoring and QA Development of Offline trigger analysis tools First studies of EMCal in High Level Trigger Offline Software for Simulations and Analysis of Data EMCal Performance and PID Deliverables: Software code to match tracks to EMCal clusters. Software code for identifying electrons from background and determination of efficiency for p+p. Analysis Techniques & Software Deliverables: Optimized jet-finder code for testing and use with charged tracks in the 2008 pp run. Software code for jet particle identification and correlations in 2008 p+p run. Ongoing Tasks: Develop techniques & software for - identifying photons and neutral pions in EMCal to high p T - identifying particle and hadronic resonance decays in 2008 p+p run - separating charm and beauty decays using electron-hadron correlations in 2008 p+p run 2008 EMCal Detector Support and Operations Conduct first cosmic ray calibrations of assembled supermodule(s) Develop EMCal on-line analysis code and calibration tools based on mips and electrons 18

19 Develop cluster unfolding and pi-zero based calibration tools Test Emcal calibration procedures in PHOS data Finalize EMCal slow controls in the ALICE environment EMCal Installation Trigger Simulations to quantify EMCal trigger performance at L0, L1 Development of triggers for Ultra-peripheral collisions Development of software tools for Online trigger calibration, monitoring and QA Development of Offline trigger analysis tools Development of High Level Trigger implementation Offline Software for Simulations and Analysis of Data EMCal Performance and PID Deliverables: Software code for - identifying electrons from background and determination of efficiency for Pb+Pb in EMCal - electron-hadron separation in EMCal - identifying photons and neutral pions in EMCal to largest p T Analysis Techniques & Software Deliverables: Software code for - identifying particle and hadronic resonance decays - measuring jet fragmentation for π, K, p, Λ, D, B and hadronic resonances in 2008 p+p - separating charm and beauty decays using electron-hadron correlations in 2008 p+p - measuring direct photon and neutral pion spectra in 2008 p+p run. - identifying vector meson (ρ, φ, J/ψ, Υ) decays in 2008 p+p run - measuring jet/leading particle yields and shapes in 2008 p+p run 2009 EMCal Detector Support and Operations Conduct cosmic ray calibrations of supermodules EMCal Installation new modules/ Commissioning / Calibration EMCal operations Trigger Continued development of trigger algorithms as EMCal installation proceeds, acceptance expands, luminosity increases Commissioning of jet trigger Continued development of HLT functionality Offline: detailed analysis of trigger performance in first large ALICE dataset Offline Software for Simulations and Analysis of Data EMCal Performance and PID Deliverables: Software code for tagging and triggering on displaced vertices for heavy flavor decays in p+p and test in p+p 19

20 Analysis Techniques & Software Deliverables: Software code for - analysis of electron-hadron correlations in Pb+Pb - vector meson (ρ, φ, J/ψ, Υ) yields and spectra in Pb+Pb - nuclear modification factors for non-photonic electrons in Pb+Pb - heavy flavor identification in Pb+Pb - fragmentation functions for identified particles in Pb+Pb - jet/leading particle yields and shapes in Pb+Pb - jet particle correlations in Pb+Pb - identifying hadronic resonances in Pb+Pb - measuring jet fragmentation for π, K, p, Λ, D, B and hadronic resonances in Pb+Pb - photon and neutral pion spectra in Pb+Pb - Ultra-Peripheral Collisions (ρ production compared to RHIC) in Pb+Pb Ongoing Tasks: Continue improvement and evaluation of techniques & software for - identifying modifications (e.g. k T broadening) of jet shapes in EMCal in Pb+Pb - identifying decays of hadronic resonances in jets in EMCal in Pb+Pb - analysis of γ-jet correlations in EMCal in Pb+Pb - jet correlations (hadron-resonance, jet-resonance) in EMCal in Pb+Pb - photon and neutral pion spectra in EMCal in Pb+Pb - separating charm and beauty decays using electron-hadron correlations in EMCal in Pb+Pb - measuring direct photon and neutral pion spectra in EMCal in Pb+Pb. - measuring jet/leading particle yields and shapes in EMCal in Pb+Pb Physics Deliverables (from 2008 LHC p+p run): Papers (p+p) on: - direct photon and neutral pion spectra at large p T - jet/leading particle yields and shapes at large p T - π, K, p, Λ, charged hadron fragmentation and spectra at large p T 2010 EMCal Detector Support and Operations Conduct cosmic ray calibrations of supermodules EMCal Installation new modules/ Commissioning / Calibration EMCal operations Trigger Final commissioning and operation of full EMCal trigger functionality Continued development of trigger algorithms and data-taking strategies as the EMCAL, ALICE and the LHC mature and luminosity increases Offline Software for Simulations and Analysis of Data EMCal Performance and PID Deliverables: Software code for tagging and triggering on displaced vertices for heavy flavor decays in Pb+Pb 20