Contact the LHC

Transcription

1 SUSY07, Karlsruhe, 31/07/ th International Conference on Supersymmetry and the Unification of Fundamental Interactions Contact the LHC Mónica L. VázuezV Acosta (CERN) on behalf of the ATLAS and CMS Collaborations

2 Search for Contact Interactions at the LHC A = ± 1 New physics at a scale Λ above the observed dijet (dilepton) mass is effectively modelled as a contact interaction. Quark compositeness New interactions from massive particles exchanged M ~ Λ M ~ Λ ŝ < Λ 6 2πA L = ( 2 Λ Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07, Contact Interaction i,j= 1 il Λ γ Λ µ il )( jl f f γ µ jl )

3 Contact Interactions in Mass Distributions Contact interaction produces increase in rate relative to QCD at high mass Observation in mass distribution alone reuires precise understanding of QCD cross section Hard to do: - Jet energy scale uncertainties give large cross section uncertainties - Parton distribution uncertainties are significant at high mass = high x and Q 2 QCD Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07, Λ CI

4 Contact Interactions in Angular Distributions Center of Momentum Frame θ* Jet Contact interaction is often more isotropic than QCD dn / dcos θ* Jet QCD Background Signal Angular distribution has much smaller systematic uncertainties than cross section vs. dijet mass Effects emerge at high mass 0 1 cos θ* Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07,

5 N/45 GeV 20 fb -1 ATLAS: Dijet Cross Section Contact Interaction Sensitivity Fast simulation 3TeV 5TeV 10 TeV 20 TeV 40 TeV QCD R dist 3TeV ATLAS Preliminary 5TeV 10 TeV 20 TeV 20 fb -1 ATLAS Preliminary p T (GeV) 0 0 N(E T > E ) T N(E T > E ) T 0 R= /,ET = 1100 GeV 0 0 N(E T E T) N(E T E T) < < CI+ QCD 40 TeV QCD p T (GeV) Luminosity to achieve sensitivity R dist =3 R dist R( Λ) R(SM) = σ Λ (TeV) Lumi 4.3 pb pb fb fb fb -1 No systematics R( Λ ) Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07,

6 N/45 GeV ATLAS: Dijet Cross Section Systematics 3TeV 30 fb-1 ATLAS Preliminary Λ=10 TeV, L=30 fb-1 5 TeV 10 TeV error PDFs 15 TeV ATLAS Preliminary 20 TeV QCD +1,2,3% central value QCD T QCD dσ dp 1% uncertainty in Energy Scale is enough to hide Λ = 20 TeV pt (GeV) Calorimeter non100 linearity = 10 TeV, fb. 1.1 ET (meas.) = ET PDF and calorimeter non linearity systematic uncertainties under study b = 0.045, 2TeV L=100 fb Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) 1 c(1 + (e / h 1)b ln ET ) S ry LA na AT limi e Pr pt (GeV) Nonlin Lin QCD -1,2,3% (GeV) ptp(gev) SUSY07, Karlsruhe, 31/07,

7 1dN Ndχ ATLAS: Dijet Angular Distributions No systematics, Fast simulation p T > 1 TeV Mjj > 4 TeV 20 fb -1 ATLAS Preliminary 3TeV 5TeV 10 TeV 20 TeV 40 TeV QCD χ = R χ η η * 1 + cosθ 1 cosθ 1 2 e = * N( χ < χ = N( χ > χ Jet θ* CM Frame Jet cut ) Rχ( Λ) R χ(sm), R1 = 2 2 cut ) σ Λ + σsm χ cut = 2.8 to maximize sensitivity Λ(TeV) Luminosity to achieve Lumi < 1 pb -1 6 pb fb fb fb -1 sensitivity R 1 =3 High-mass dijet angular distributions with first tens of pb -1 will allow the discovery of uark compositeness if the constituent interaction constant is Λ = 3-5 TeV Systematics are expected to be much smaller than for dσ/dp T Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07, χ

8 CMS: Dijet Cross Section Contact Interaction Sensitivity Systematic uncertainties on the cross section versus dijet mass are large 1 fb Jet Energy -1 CMS estimates ±5 % is achievable Changes dijet mass cross section 30-70% Parton Distributions CTEQ6 uncertainty Resolution Bounded by difference between hadron level and detector level jets Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07,

9 CMS: Dijet Angular Distributions Dijet Ratio = N( η <0.5)/N(0.5< η <1) Simple measure of the most sensitive part of the angular distribution Measure dijet ratio as a function of mass Systematics on the dijet ratio are small Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07,

10 Ratio N( η <0.5)/N(0.5< η <1) CMS: Dijet Ratio Systematic Uncertainties Corrected Dijet Mass (GeV) Absolute Jet Energy Scale No effect on QCD dijet ratio: flat vs dijet mass Causes 5% uncertainty in Λ Relative Energy Scale Energy scale in η <0.5 vs. 0.5 < η < 1 Estimate ±0.5 % is achievable in Barrel Changes ratio between ± Ratio N( η <0.5)/N(0.5< η <1) Corrected Dijet Mass (GeV) Resolution No change to the ratio when changing resolution Systematics bounded by statistics: 0.02 Parton Distributions CTEQ6.1 uncertainties, Systematics on ratio <0.02 No testbeam data above 300 GeV. Discovery range is in the regime where the calorimetric response is extrapolated Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07,

11 CMS: Dijet Ratio Significance of Contact Interaction Signal Significance in σ Significance in σ Significance in σ 1/Λ(TeV) 1/Λ(TeV) 1/Λ(TeV) Left-Handed Quark Λ + for 100 pb -1 Λ + for 1 fb -1 Λ + for 10 fb -1 Contact Interaction (TeV) (TeV) (TeV) 95% CL Stat Only Exclusion All Syst σ Stat Only Discovery All Syst D0 excludes at 95%CL scales of Λ + <2.7 TeV with 100 pb -1 (hep-ex/ ) Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07,

12 CMS: Dimuon Contact Interaction sensitivity Events 100 fb -1 Events 100 fb TeV 1-6 TeV Dimuon Mass (GeV) Dimuon Mass (GeV) Main sensitivity from cross ~ 1 TeV and higher Λ f Drell-Yan CI f Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07,

13 CMS: Dimuon Double Ratio (100 fb -1 ) Double Ratio Absolute Efficiency, EW corrections,... cancel out in a ratio mass bin GeV for normalization SM valid - Tevatron u uark PDF dominant which has the smallest uncertainty R i DATA = N id /N 0D = σ id.ε id / σ 0D.ε 0 D R i = N i /N 0 = σ i.ε i / σ 0.ε 0 Double ratio: DR i = R i DATA / R i If theory understanding and detector modeling are both perfect DR i = 1 Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07,

14 CMS: Dimuon Contact Interactions Discovery Reach Contact Interaction Scale TeV 5σ Discovery Contact Interaction Scale TeV 95% CL Exclusion Luminosity fb -1 Luminosity fb -1 Up to 10 fb -1 (higher for Λ + ) dominated by statistical errors Even 30 % systematic errors have small impact Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07,

15 Summary Contact interactions at a scale Λ are generally observed before any exchanged particle is directly seen Many techniues have been developed and show good results with low systematic effects: - Angular distributions and simple angular ratios (jets) - Double ratio (dimuons) Sensitivity of the LHC experiments to contact interactions has been investigated -The first hundred pb -1 of data will allow the discovery of contact interactions with Λ up to ~5 TeV - 100fb -1 of data allows discovery of compositeness up to ~30TeV Contact Interactions at the LHC, Mónica L. Vázuez Acosta (CERN) SUSY07, Karlsruhe, 31/07,