The TOTEM experiment at the LHC: results and perspective

Transcription

1 The TOTEM experiment at the LHC: results and perspective Edoardo Bossini Università degli studi di Siena and INFN-Pisa (on behalf of the TOTEM collaboration) Trieste, 24 Settembre 2013 OUTLINE: Detector overview Total, elastic and inelatic pp cross section Diffractive physics Future upgrades Edoardo Bossini, Trieste, 24 Settembre

2 Totem detector TOTEM detectors Edoardo Bossini, Trieste, 24 Settembre

3 Totem detector: T1 T1: equally spaced planes of six trapezoidal Cathode Strip Chambers (CSC) Distance from IP5 ~ 7.5 m Edoardo Bossini, Trieste, 24 Settembre

4 Totem detector: T2 T1: almost semi-circular Gas Electron Multi-plier (GEM) detectors per arm Distance from IP5 ~ 13.5 m Edoardo Bossini, Trieste, 24 Settembre

5 Totem detector: RP Very close to the beam, in secondary vacuum 4 stations, 2 units per station, 3 pots per unit(2 vertical, 1 horizontal) 10 planes per pot, 512 edgeless Si strips each Distance from IP5 ~ 147,220 m Edoardo Bossini, Trieste, 24 Settembre

6 Totem detector CMS T1 T1 T2 T2 RP220 T2 T1 T1 T2 RP220 CMS Edoardo Bossini, Trieste, 24 Settembre

7 LHC optic,, Θ, Θ, Transport matrix,, Θ, Θ, Θ Θ Θ + Θ, effective lenghts(sensitivity to scattering angle), magnifications(sensitivity to vertex position) dispersion (sensitivity to Δ ), ~ Edoardo Bossini, Trieste, 24 Settembre

8 LHC optic,, Θ, Θ, Transport matrix,, Θ, Θ, Θ Θ Θ + Θ 90m@220F (,, 0) Edoardo Bossini, Trieste, 24 Settembre

9 Total, elastic and inelastic pp cross sections

10 Total cross section measurements elastic observation only d d ( = 0.14 [COMPETE]) independent independent 1 16 d d 1 Edoardo Bossini, Trieste, 24 Settembre

11 Elastic Scattering: event selection in RP Raw hit distribution Elastic selection Beam halo Low-ξ p Aperture limitation The event selection requires the collinearity of the two outgoing protons, the suppression of the diffractive events and the comparison of the horizontal vertex position reconstructed from the left and right arms. Edoardo Bossini, Trieste, 24 Settembre

12 Elastic Scattering: vertex reco RP beam approach Aperture limitation For elastic proton Θ Θ Edoardo Bossini, Trieste, 24 Settembre

13 7 TeV extrapolation Edoardo Bossini, Trieste, 24 Settembre

14 Inelastic Scattering: corrections Search for event with at least 1 «primary» track in T2 Pile up and trigger efficiency estimated with zero-bias triggered events Beam gas estimated triggering on non colliding bunches T2 recostruction eficiency with MC studies Edoardo Bossini, Trieste, 24 Settembre

15 Inelastic Scattering T2 T1 T1 T2 From T1,T2 data Track in T1 (& empty T2) Edoardo Bossini, Trieste, 24 Settembre

16 Inelastic Scattering Rap gap T2 T1 T1 T2 Infered from T1 data Rapidity gap in T2 for 1-arm events (hadronization fluctuation) Edoardo Bossini, Trieste, 24 Settembre

17 Inelastic Scattering T2 T1 T1 T2 Central diffraction (T1,T2 empty) From MC, small correction with big uncertanties Edoardo Bossini, Trieste, 24 Settembre

18 Inelastic Scattering T2 T1 T1 T2 MC based Low mass diffraction (T1,T2 empty) Edoardo Bossini, Trieste, 24 Settembre

19 Total cross 7 TeV EPL 95 (2011) EPL 96 (2011) EPL 101 (2013) EPL 101 (2013) EPL 101 (2013) elastic observation only d d ( = 0.14 [COMPETE]) June 2011 : Oct 2011 : independent independent 1 16 d d Edoardo Bossini, Trieste, 24 Settembre

20 Total cross 7 TeV EPL 95 (2011) EPL 96 (2011) EPL 101 (2013) EPL 101 (2013) EPL 101 (2013) elastic observation only d d ( = 0.14 [COMPETE]) June 2011 : Oct 2011 : independent independent 1 16 d d d d 16 1 measurements ρ Edoardo Bossini, Trieste, 24 Settembre

21 7 TeV: results comparison Edoardo Bossini, Trieste, 24 Settembre

22 8 TeV results Phys.Rev.Lett. 11, d d Luminosity independent 0.14±0.007 [COMPETE] = (101.7±2.9) mb From, measurements Edoardo Bossini, Trieste, 24 Settembre

23 Cross sections summary Edoardo Bossini, Trieste, 24 Settembre

24 Very low measurement Measurement of require the study of the Coulomb Nuclear interference region down to ~6 10 of 1 needed! ħ ħ = relative Coulomb-nuclear phase G(t) = nucleon el.-mag. form factor /, 0 Edoardo Bossini, Trieste, 24 Settembre

25 Coulomb interference Analysis aim: 1. Measure d d at the smallest possible proton t (where the Coulomb interaction can be probed). 2. Fit the data with many theoretical models: evaluate the agreement, extract physics parameters (, ), further improve the measurement. Edoardo Bossini, Trieste, 24 Settembre

26 : preliminary result Edoardo Bossini, Trieste, 24 Settembre

27 Charged-particle pseudorapidity density EPL 98 (2012) Analysis with only T2 telescope , 40 Data Vs MC prediction Since about 80% of the T2 reconstructed tracks are secondaries, it has been crucial to find a procedure for primary charged particle identification with strong discriminating power. Analysis has been performed on each quarter independently 7 Edoardo Bossini, Trieste, 24 Settembre

28 Eta distribuiton with CMS New analisys ongoing for 8, with CMS! Both CMS and TOTEM analysis obtained triggering with T2, on the same events. Same CMS-TOTEM event slection (at least a track reconstructed in T2) Edoardo Bossini, Trieste, 24 Settembre

29 Diffractive physics

30 Event topology RP RP T2 T1 CMS Edoardo Bossini, Trieste, 24 Settembre

31 CERN-PH-EP Double Diffractive This measurement uses data collected in October 2011 at 7. The data were collected with the T2 minimum bias trigger. No leading proton only inelastic detector used Aim: Measurement of soft double diffractive cross section with particle visible to TOTEM T2 ( ). Edoardo Bossini, Trieste, 24 Settembre

32 Double Diffractive: analysis Event selection: trigger with T2, at least one track in both T2 hemispheres, no track in T1 («0T1+2T2» topology). ND (Non Diffractive) background estimated scaling the MC prediction using a data sample dominated by ND (tracks on T1 and T2 on both sides) SD (Single Diffractive) background from data using a data sample dominated by SD (tracks only in one side of T2) and requiring proton in the RP Four additional exclusive data samples defined for testing the background model. Edoardo Bossini, Trieste, 24 Settembre

33 Double Diffractive: results for events where for both diffractive masses Edoardo Bossini, Trieste, 24 Settembre

34 Single Diffractive Edoardo Bossini, Trieste, 24 Settembre

35 Single Diffractive: analysis SD event selected requiring only 1 proton in the RP in events triggered by T2 Diffractive mass can be obtained from the rapidity gap estimation base on charged particle track in T1 and T2 (Δ ). Better resolution for low-medium mass. SD events classified into 4 categories,based on the rapidity gap: Requiring a proton allow strong background rejection Inelastic+beam gas beckground estimated from data, esing mirrored events (diffractive mass and proton on same side) Edoardo Bossini, Trieste, 24 Settembre

36 Single Diffractive: preliminary results Low Mass Medium Mass Correction included: Trigger efficiency Recostruction efficiency Proton acceptance Background substraction Extrapolation to t=0 High Mass Missing: resolution and beam divergence effect Uncertainty (estimated): ~15% ; ~20% Very preliminary: Very High masses measurement ongoing Edoardo Bossini, Trieste, 24 Settembre

37 Central diffraction (Totem/CMS) Cuts: Vertex 1 Rp near edge removed (background suppression) Rp top-bot/bot-top topology 1.5%, better resolution FSC empty (suppress back.) CMS RP CMS RP MM(pp) = 244 GeV; M(CMS) = 219 GeV Jets 65,45,27 GeV Σ (CMS) = 3.4 GeV

38 Consolidation and upgrade

39 Current Setup 2 vertical RP (strip) ~1.5 ~ Near 147 Far (200m) 220 Near 220 Far 2 vertical RP (strip) 2 vertical RP (strip) 2 vertical RP (strip) 6 (230m) 1 horiz. RP (strip) 1 horiz. RP (strip) 1 horiz. RP (strip) 1 horiz. RP (strip) ~147 Outgoing beam ~220 CD physics (small cross section) High luminosity needed but How to deal with pile up? Edoardo Bossini, Trieste, 24 Settembre

40 New LHC optics Edoardo Bossini, Trieste, 24 Settembre

41 RP multitrack capability Current limitation: not able to reconstruct events with 2 tracks in same pot Patch 1: move 147 stations to 210 meters and tilt Far RP by ~8 True tracks reco track+ghost Tilt(degree) Patch 2 (long term): replace existing strip detectors with pixel detectors Edoardo Bossini, Trieste, 24 Settembre

42 Timing detector Vertex reconstruction by measuring the time of flight differences of the proton Improve physics capability at moderate pile-up (high-,vertical pots) Reduce trigger rates unisng proton left-right correlation without killing CD signal Signal background simuation has been performed usind real data ( ~9, 8, ) to: estimate pile-up scenario in timing dector for 30 optimizing timing sensor cell find effective trigger strategy Edoardo Bossini, Trieste, 24 Settembre

43 Detector segmentation Timing pixel have big impact in detector efficiency Inefficiency due to multiplicity cut reduced by factor ~ 2 w.r.t. fixed square cell size!! Edoardo Bossini, Trieste, 24 Settembre

44 Trigger strategy Trigger strategy: Apply multiplicity cut Edoardo Bossini, Trieste, 24 Settembre

45 Trigger strategy Trigger strategy: Apply multiplicity cut Compute for all combination Edoardo Bossini, Trieste, 24 Settembre

46 Trigger strategy Trigger strategy: Apply multiplicity cut Compute for all combination Select vertex displaced (highest prob. to be isolated) Longitudinal distribution of vertices separated by at least 1 cm from the others Edoardo Bossini, Trieste, 24 Settembre

47 Trigger strategy Trigger strategy: Apply multiplicity cut Compute for all combination Select vertex displaced (highest prob. to be isolated) Send list to CMS HLT to compare with CMS isolated vertex list Few KHz with purity 30%! Longitudinal distribution of vertices separated by at least 1 cm from the others Edoardo Bossini, Trieste, 24 Settembre

48 Trigger strategy Trigger strategy: Apply multiplicity cut Compute for all combination Select vertex displaced (highest prob. to be isolated) Send list to CMS HLT to compare with CMS isolated vertex list Longitudinal distribution of vertices separated by at least 1 cm from the others Few KHz with purity 30%! Ongoing studies on: Clock distribution Detector impedance DAQ & Trigger Edoardo Bossini, Trieste, 24 Settembre

49 Final setup 5 (200m) ~210 Outgoing beam ~ Near 220 Far 2 vertical RP (strip) 1 horiz. RP (strip/pixel) 2 vertical RP (strip) 1 horiz. RP (tilt/pixel) 2 vertical RP (strip) 1 horiz. RP (strip) ~220 ~5 220 Near 220 Far Timing 2 horiz. RP (timing) 2 vertical RP (strip/timing) 1 horiz. RP (strip) TCL 6 6 (230m) Highly flexible/scalable system! Different combinations of tracking+timing can be used to make different physics Edoardo Bossini, Trieste, 24 Settembre

50 Many phisics analysis have been performed.. Total, elastic and inelastic pp cross section at 7 and 8 Foward charged particle pseudorapity distribution at 7 Double diffractive cross section (3.4 8 ) indirect measurements at 7 many others are ongoing Conclusion Hadronic/coulomb interference, measure of at 8 Soft diffractive cross section for Foward charged particle pseudorapity distribution at 8 (TOTEM/CMS joint analysis) Other analysis with CMS (softcd and CD with dijets, SD and dijets, pa, ) and many others will begin after the consolidation/upgrade program (and the LHC restart )!! Thanks for your attention Edoardo Bossini, Trieste, 24 Settembre

51 Totem detector: coverage CMS RP T2 T2 T1 T1 T1 T1 T2 T2 RP CMS Edoardo Bossini, Trieste, 24 Settembre

52 DataSet Data at 7, 90 Data at 8, 90 Edoardo Bossini, Trieste, 24 Settembre

53 Elastic cut 1-2 track collinearity 3-4 low cut. If 0 reconstuction equation are invalid 5-6 low cut. If 0 correlation between position and track angle is lost 7 horizontal vertex comparison between opposite arms. Very strong cut Edoardo Bossini, Trieste, 24 Settembre

54 8 TeV extrapolation uncertainties Very good undertanding of beam optic needed!! Edoardo Bossini, Trieste, 24 Settembre

55 Elastic scattering uncertainties (7TeV) Edoardo Bossini, Trieste, 24 Settembre

56 Elastic scattering: model comparison Edoardo Bossini, Trieste, 24 Settembre

57 7 TeV results summary Edoardo Bossini, Trieste, 24 Settembre

58 ZImpact Edoardo Bossini, Trieste, 24 Settembre

59 High eta pseudorapidity correction Edoardo Bossini, Trieste, 24 Settembre

60 Pseudorapidity formula Edoardo Bossini, Trieste, 24 Settembre

61 Pseudorapidity uncertainties (7TeV) Edoardo Bossini, Trieste, 24 Settembre

62 T1/T2 acceptance for diffratctive masses Edoardo Bossini, Trieste, 24 Settembre

63 Models for Hadron/Coulomb region Edoardo Bossini, Trieste, 24 Settembre

64 DPE Cross section Edoardo Bossini, Trieste, 24 Settembre

65 Proton CD and mass acceptance Edoardo Bossini, Trieste, 24 Settembre

66 Segmentation for vertical RP Edoardo Bossini, Trieste, 24 Settembre

67 Cilindrical pots Edoardo Bossini, Trieste, 24 Settembre

68 Cilindrical pots Edoardo Bossini, Trieste, 24 Settembre