Channels & Challenges New Physics at LHC

Transcription

1 Channels & Challenges New Physics at LHC Jürgen Reuter Carleton University, Ottawa Southampton, 15. January 2007

2 The success of the Standard Model Standard Model describes microcosm gauge interactions: strong electroweak broken to electromagnetic Higgs mechanism Measurement Fit O meas O fit /σ meas α had (m Z ) (5) ± m Z [GeV] ± Γ Z [GeV] ± σ 0 had [nb] ± R l ± A fb 0,l ± A l (P τ ) ± R b ± R c ± A 0,b fb ± A 0,c fb ± A b ± A c ± A l (SLD) ± sin 2 θ lept eff (Q fb ) ± m W [GeV] ± Γ W [GeV] ± m t [GeV] ± Standard Model tested better than 1 % No significant deviations found since 1970s Theory and Experiment agree

3 Why New Physics?? Electroweak Symmetry Breaking, Higgs? Dark Matter: m DM 100 GeV? 28 free parameters? 3 families? unification, gravity M H [GeV] Λ[GeV] Hierarchy/Fine-Tuning Problem Quantum corrections to Higgs mass are sensitive for cut-off Λ δm 2 H Λ GeV 2 = ( ) GeV 2 Protective Symmetry?

4 Why New Physics?? Electroweak Symmetry Breaking, Higgs? Dark Matter: m DM 100 GeV? 28 free parameters? 3 families? unification, gravity α i U(1) SU(2) SU(3) Standard Model µ (GeV) M H [GeV] Λ[GeV] Hierarchy/Fine-Tuning Problem Quantum corrections to Higgs mass are sensitive for cut-off Λ δm 2 H Λ GeV 2 = ( ) GeV 2 Protective Symmetry?

5 Supersymmetry Little Higgs Spin-statistics: Corrections from bosons and fermions cancel connects gauge and space-time symmetries Global symmetries: Corrections from like-statistics particles cancel Higgs: Goldstone-Boson of spontan. broken global symmetry Q J 1 H H 0 Q G 1 G 1 [H G 2 G 1, H 2] 0 1 /H 1 H /H 2 H Ó ÓÒ ÖÑ ÓÒ multiplets of equal-mass fermions & bosons SUSY broken M H protected to all orders embedded in grand unified theory R-parity: dark matter collective breaking of global symmetries protects Higgs mass M H protected at first order strongly TeV T -parity: dark matter

6 Characteristics of Standard Model Extensions O( 10 TeV) O(1 TeV) O(250 GeV) F v Λ Scale Λ: hidden sector, symmetry breaking Scale F : new particles Scale v: Higgs, W/Z, l ±,... Rich spectrum of new Terascale, complicated decay structures SUSY H, A H ± q L t b2 2 q R b1 t 1 χ 0 4, χ± 2 M[TeV] 1.25 g χ Φ Φ ±± Φ ± Φ P Z γ Little Higgs W ± T U, C h τ 2 ν l τ 1 ll lr χ 0 2, χ± 1 t χ h η W ± Z t

7 Constraints on new models? Flavour structure: Meson mixing & rare decay modes, CP violation Astrophysical constraints: relic abundance Gauge structure: electroweak precision observables

8 η J. Reuter Channels & Challenges New LHC Southampton, Constraints on new models? Flavour structure: Meson mixing & rare decay modes, CP violation Astrophysical constraints: relic abundance Gauge structure: electroweak precision observables m 2 [ev 2 ] KARMEN2 LSND NOMAD Cl Ga Bugey K2K CHOOZ SNO ν e ν X ν µ ν τ ν e ν τ ν e ν µ NOMAD Super-K+SNO +KamLAND CDHSW CHORUS NOMAD BNL E776 SuperK CHORUS PaloVerde KamLAND 0.5 Super-K excluded area has CL > 0.95 ε K sin 2β V ub /V cb sol. w/ cos 2β < 0 (excl. at CL > 0.95) i 4 C K M γ f t t e r EPS tan 2 θ ρ α γ γ α excluded at CL > 0.95 β T α m d m s & m d ε K U 0 m t = ± 2.9 GeV m H = GeV sin 2 θ lept eff 68 % CL S m H m t m W prel. T Γ ll mh= 700GeV LHM F = 3.5 TeV 400GeV 250GeV 120GeV SM Kilian/JR, 2003 LHM F = 4.5 TeV S New particle scale F 1 3 TeV

9 Direct Searches: Large Hadron Collider CERN: from 2007/08 pp collider s = 14 TeV

10 É J. Reuter Channels & Challenges New LHC Southampton, The Challenge of LHC É Partonic subprocesses: qq, qg, gg No fixed partonic energy proton - (anti)proton cross sections σ (nb) σ tot Tevatron σ b σ jet (E jet T > s/20) σ W σ Z σ jet (E jet T > 100 GeV) σ t σ jet (E jet T > s/4) LHC events/sec for L = cm -2 s -1 Â Ø High event rates for t, W/Z, H, huge backgrounds Cuts for background ÓÐÐº reduction p T p p η 10-5 σ Higgs (M H = 150 GeV) σ Higgs (M H = 500 GeV) s (TeV) e

11 The Challenge of LHC Partonic subprocesses: qq, qg, gg No fixed partonic energy proton - (anti)proton cross sections σ (nb) σ tot Tevatron σ b σ jet (E jet T > s/20) σ W σ Z σ jet (E jet T > 100 GeV) LHC events/sec for L = cm -2 s -1 High event rates for t, W/Z, H, huge backgrounds ÓÖÛ Ö Cuts for background ÓÐÐº ÒØÖ Ð reduction σ t σ jet (E jet T > s/4) η = 5 η = σ Higgs (M H = 150 GeV) σ Higgs (M H = 500 GeV) s (TeV) η = 0

12 New Physics: Observables/Precision Measurements Signals for New Physics: /E T, high-p T jets, many hard leptons, but: Which model? q L χ 0 2 q 1 2 R 1 χ 0 1 Cascade decays: mass differences from endpoints of decay spectra Spin of new particles: Angular distribution,... Determining the model: Measurement of coupling constants Precise prediction for signal and background Consideration of cuts Distributions: dσ/dx, X = cos θ, η, p T,... Multi-particle final states: 2 4 bis 2 10 Quantum corrections: real and virtual Events/1 GeV/100 fb m(ll) (GeV)

13 Simulations: O Mega / Whizard Matrix Element Generator O Mega: Ohl, 2000/01; M.Moretti/Ohl/JR, 2001 Multi-purpose Event Generator Whizard: Ohl, 1996; Kilian, 2000; Kilian/Ohl/JR, 2007 Multi-Channel adaptive Monte-Carlo integration very well tested JR et al., 2006; Hagiwara/... /Krauss/Plehn/JR/..., 2006 Virtual Corrections: NLO Monte Carlo NLO MC for e + e χ + 1 χ 1 LO 200 NLO Kilian/JR/Robens, 2006 e e + χ 1 χ + 1 σtot [fb] Arbitrary NLO s [GeV]

14 Sbottom production at LHC Hagiwara/... /JR/..., 2006 b 1 production with subsequent decay b 1 χ 0 1 b Process A 1 A 2 P ( ) F 1 F 2, 3 different levels: Narrow Width σ(a 1 A 2 P ) BR(P F 1 F 2 ) Breit-Wigner σ(a 1 A 2 P ) Full matrix element σ(a 1 A 2 F 1 F 2 ) M 2 P Γ2 P (s M 2 P )2 +Γ 2 P M 2 P BR(P F 1 F 2 ) 10 5 evt/10 GeV L = 100 fb evt/10 GeV L = 100 fb pt(b/ b) [GeV] missing pt [GeV] pp b b χ 0 1 χ0 1 Main background: gg b bν ν Signal jets harder

15 Off-Shell effects at LHC: 6000 evt/5 GeV L = 100 fb evt/5 GeV L = 100 fb 1 PS: Harder jet more central Off-Shell effects (b bz ): only for low p T,b is cut out Not generally guaranteed pt(b/ b) [GeV] η(b/ b) Prozeß σ BR [fb] σ BW [fb] σbw cut Zh HA χ 0 1 χ χ 0 1 χ χ 0 1 χ b 1 b Sum Exact ILC: e + e b b χ 0 1 χ0 1 [800 GeV] Cuts for M b b eliminate other resonances

16 Real corrections: bottom-jet radiation K. Hagiwara/... /JR/..., 2006 g b b-splitting, b-isr als combinatorial background pp χ 0 1 χ0 1 b bb b: diagrams, 22 color flows, 4000 PS channels σ(pp b b χ 0 1 χ0 1 ) = 1177 fb σ(pp b bb b χ 0 1 χ0 1 ) = fb Forward discrimination between ISR and decay-b jets difficult: 2000 evt/5 GeV L = 100 fb 1 evt/5 GeV L = 100 fb pt(b/ b) [GeV] Only the most forward b jet considerably softer pt(b/ b) [GeV]

17 Real corrections: bottom-jet radiation K. Hagiwara/... /JR/..., 2006 g b b-splitting, b-isr als combinatorial background pp χ 0 1 χ0 1 b bb b: diagrams, 22 color flows, 4000 PS channels σ(pp b b χ 0 1 χ0 1 ) = 1177 fb σ(pp b bb b χ 0 1 χ0 1 ) = fb Only minor differences in p T,b, PDF: maximum for smaller value [arbitrary units] [arbitrary units] pt(b/ b) [GeV] missing pt [GeV] shifted to smaller /p T : light particles balance out the event

18 What if not SUSY?

19 Pseudo-Axions in Little Higgs Kilian/Rainwater/JR, 2004, 2006; JR, 2007 gauged U(1) group: Z ungauged: η couples to fermions like a pseudoscalar m η 400 GeV SM singlet, couplings to SM particles v/f suppressed η axion-like particle: BR [η] b b τ + τ c c gg γγ µ + µ Zh mη [GeV] Anomalous U(1): 1 F α s 8π 2 ηf µν F ρσ ɛ µνρσ U(1) explicitly broken Axion limits from astroparticle physics not applicable

20 The Glimpse of a Discovery Kilian/Rainwater/JR, 2004, 2006 LHC: Gluon fusion, diphoton signal für m η 200 GeV, 7σ possible LHC: T tη ILC: e + e t tη Godfrey/Rainwater/JR

21 The Glimpse of a Discovery Kilian/Rainwater/JR, 2004, 2006 LHC: Gluon fusion, diphoton signal für m η 200 GeV, 7σ possible LHC: T tη ILC: e + e t tη Godfrey/Rainwater/JR e e + t tb b #evt/2 GeV m η = 50 GeV 100 s = 800 GeV L = 1 ab 1 g ttη = M inv (b b) [GeV]

22 The Glimpse of a Discovery Kilian/Rainwater/JR, 2004, 2006 LHC: Gluon fusion, diphoton signal für m η 200 GeV, 7σ possible LHC: T tη ILC: e + e t tη Godfrey/Rainwater/JR ZHη coupling forbidden in Product Group Models Discrimator of diff. model classes { } H Zη llbb gg η ZH llbb, llljj

26 Outlook LHC: new era of physics Higgs mechanism New particles, symmetries: SUSY, Little Higgs Pheno: precision calculations/simulations of multi-particle final states Exciting times ahead!

27 Outlook LHC: new era of physics Higgs mechanism New particles, symmetries: SUSY, Little Higgs Pheno: precision calculations/simulations of multi-particle final states Exciting times ahead! There is light at the end of the tunnel!

28

29 Ideas for New Physics since 1970 (1) New Ingredients Technicolour: Higgs a bound state of strongly-interacting particles (2) Symmetries for cancellation of quantum corrections Supersymmetry: Spin-statistics corrections from bosons and fermions cancel each other Little Higgs models: Global symmetries corrections from like-statistics particles cancel each other (3) Nontrivial Space-time structure eliminates hierarchy Additional space dimensions: gravity appears only week Noncommutative space-time: coarse-grained space-time (4) Ignoring the Hierarchy Anthropic Principle: parameters have their values, because we (can) measure them

30 Constraints on new models? Flavour structure: K, D, B mixing, rare K, D, B decay modes CP violation: CP asymmetries, electric dipole moments Astrophysical constraints: relic abundance Gauge structure: electroweak precision observables

31 Constraints on new models? Z L Z L Z L Z L T ρ Z T Z T Z T Z T S T mh= 700 GeV 400 GeV 250 GeV 120 GeV 0.2 LHM F = 3.5 TeV SM LHM F = 4.5 TeV S Tree-Level mixing Z, Z induces big corrections Scale F 1 3 TeV Higgs compensates for Z Naturally heavy Higgs in Little Higgs Models Kilian/JR, 2003 Kilian/JR, 2003

32 Tests and Checks: Example MSSM JR et al., 2005; K. Hagiwara/W. Kilian/F. Krauss/T. Ohl/T. Plehn/D. Rainwater/JR/S. Schumann, 2006 MSSM: spectrum doubled, 100 parameters, 5000 vertices Implementation enforces tests and consistency checks Unitarity check: σ(2 2, s), σ(2 3, s) const or 1/s Gauge invariance: Ward- and Slavnov-Taylor identities Supersymmetry: Ward-/Slavnov-Taylor identities JR, 2002; Ohl/JR, 2002 Comparison of independent codes (O(600) processes): JR et al., 2005; K. Hagiwara/... /JR/..., 2006 Reference: ff X Process stat. Madgraph/Helas Whizard/O Mega Sherpa/A Megic 0.5 TeV 2 TeV 0.5 TeV 2 TeV 0.5 TeV 2 TeV uu ũ L ũ L 716.9(1) (4) (4) uu ũ R ũ R 679.6(1) (4) (4) uu ũ L ũ R (6) (5) (6) dd d L d L 712.6(1) (4) (4) dd d R dr 667.4(1) (4) (3) dd d L dr (6) (5) (7)

33 SUSY Exotics at LHC Gauge couplings run: dg a d log µ = g3 a 16π B 2 a, B a depends on field content Sparticles make couplings unify e.g.: SU(5) SU(3) c SU(2) w U(1) Y Doublet-triplet splitting problem: Proton decay by Higgs partner D /α1 1/α2 1/α3 Running of 1/α, SM Extended MSSM Higgs sector relaxed Higgs bounds (light pseudoscalars) possibly large invisible decay ratio lightest unhiggs: H parity protected dark matter dark matter mix: interesting relic abundance (relaxes all neutralino bounds!) Pair production of unhiggses/unhiggsinos, cascade decays log (µ [GeV])

34 SUSY Exotics at LHC Gauge couplings run: dg a d log µ = g3 a 16π B 2 a, B a depends on field content Sparticles make couplings unify e.g.: SU(5) SU(3) c SU(2) w U(1) Y Doublet-triplet splitting problem: Proton decay by Higgs partner D Dqq, Dlq /α1 1/α2 1/α3 Running of 1/α, MSSM Extended MSSM Higgs sector relaxed Higgs bounds (light pseudoscalars) possibly large invisible decay ratio lightest unhiggs: H parity protected dark matter dark matter mix: interesting relic abundance (relaxes all neutralino bounds!) Pair production of unhiggses/unhiggsinos, cascade decays log (µ [GeV])

35 SUSY Exotics at LHC Gauge couplings run: dg a d log µ = g3 a 16π B 2 a, B a depends on field content Sparticles make couplings unify e.g.: SU(5) SU(3) c SU(2) w U(1) Y Doublet-triplet splitting problem: Proton decay by Higgs partner D Dqq, Dlq Kilian/JR, Running of 1/α, MSSM with 1 [(Hu, D) (Hd, D c )] SU(3)c SU(2)L SU(2)R 1/α1 1/α2 1/α3 1/α1 Extended MSSM Higgs sector relaxed Higgs bounds (light pseudoscalars) possibly large invisible decay ratio lightest unhiggs: H parity protected dark matter dark matter mix: interesting relic abundance (relaxes all neutralino bounds!) Pair production of unhiggses/unhiggsinos, cascade decays log (µ [GeV])

36 SUSY Exotics at LHC Gauge couplings run: dg a d log µ = g3 a 16π B 2 a, B a depends on field content Sparticles make couplings unify e.g.: SU(5) SU(3) c SU(2) w U(1) Y Doublet-triplet splitting problem: Proton decay by Higgs partner D Dqq, Dlq Kilian/JR, Running of 1/α, MSSM with 1 [(Hu, D) (Hd, D c )] SU(4)c SU(2)L SU(2)R 1/α1 1/α2 1/α3 1/α log (µ [GeV]) Extended MSSM Higgs sector relaxed Higgs bounds (light pseudoscalars) possibly large invisible decay ratio lightest unhiggs: H parity protected dark matter dark matter mix: interesting relic abundance (relaxes all neutralino bounds!) Pair production of unhiggses/unhiggsinos, cascade decays

37 SUSY Exotics at LHC Gauge couplings run: dg a d log µ = g3 a 16π B 2 a, B a depends on field content Sparticles make couplings unify e.g.: SU(5) SU(3) c SU(2) w U(1) Y Doublet-triplet splitting problem: Proton decay by Higgs partner D Dqq, Dlq Kilian/JR, Running of 1/α, MSSM with 3 [(Hu, D) (Hd, D c )] SU(4)c SU(2)L SU(2)R 1/α1 1/α2 1/α log (µ [GeV]) (Down-type) Leptoquarks, Leptoquarkinos 3 generations at TeV scale produced in gluon fusion, single production final states: tτ, bντ, tτ,... if flavor symmetry leaves traces: gq Dl enhanced, decays tµ, te Extended neutralino sector like in NMSSM