XXXIV Int. Symp. on Multiparticle Dynamics, Sonoma County, July 29, 2004 ISMD Rohlf p.1/50 Physics with Jets at the LHC Jim Rohlf Boston University
Outline Introduction Detectors and expected performance Event Rates and Triggering Calibration Missing transverse energy SUSY Higgs (taus and b tagging) Z Compositeness Heavy Ion Collisions Summary and Outlook ISMD Rohlf p.2/50
Documents ISMD Rohlf p.3/50
ISMD Rohlf p.4/50 LHC Protons The gaps are important for synchronization! LHC/PS = 42.4 (39 PS fill) (72 bunches/ps fill) = 2808 bunches 88924 ns t = 3564 ns = 24.95 ns Abort gap = 3 µs used for fast reset
ISMD Rohlf p.5/50 Charged particles 10 9 10 4 ID Entries Mean RMS 100 189538 0.6047 0.5757 8 7 10 3 6 5 14 TeV 10 2 14 TeV 4 3 10 2 1 0 0 0.5 1 1.5 2 2.5 dn/dη (charged particles) 1 0 2 4 6 8 10 p T of charged particles (GeV)
SLHC LHC parameters pp c.m. energy luminosity collision rate W/Z 0 rate bunch spacing 14 TeV 10 34 cm 2 s 1 1 GHz 1 khz 25 ns interactions per crossing 20 dn ch per crossing 10 5 cm 2 s 1 dη track flux @ 1 m 10 5 cm 2 s 1 rad. dose @ 1 m for 2500 fb 1 1 kgy First physics expected at low luminosity : 2 10 33 cm 2 s 1 ISMD Rohlf p.6/50
ISMD Rohlf p.7/50 Kinematics and Cross Section 10 9 LHC parton kinematics 10 5 inclusive jet cross section 10 8 10 7 x 1,2 = (M/14 TeV) exp(±y) Q = M M = 10 TeV 10 4 10 3 10 2 QCD-LO, µ=e T /2 CTEQ4M CTEQ4HJ MRST Q 2 (GeV 2 ) 10 6 10 5 10 4 10 3 10 2 10 1 M = 10 GeV M = 100 GeV M = 1 TeV y = 6 4 2 0 2 4 HERA fixed target 10 0 10-7 10-6 10-5 10-4 10-3 10-2 10-1 10 0 x 6 d 2 σ/dηde T η=0 (nb/tev) 10 1 10 0 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 s = 1.8 TeV s = 14 TeV 0 1 2 3 4 5 E T (TeV)
Detectors overview tracking in B field EM calorimetery had. calorimetry muon detectors A Toroidal Large hadron collider AparatuS (ATLAS) 7 ktons 0.5 T toroid, 2 T solenoid 25 m 46 m Compact Muon Solenoid (CMS) 14 ktons 4 T solenoid 15 m 22 m ISMD Rohlf p.8/50
ISMD Rohlf p.9/50 ATLAS and CMS zeroth-order difference ATLAS Large magnet cost (40%) good stand-alone muon resolution (BL 2 ) less resources spent on ECAL and tracking CMS Lower magnet cost (25%) high-resolution tracker high-performance ECAL
Detector technology CMS ATLAS Tracking: inner pixels pixels barrel silicon strips silicon strips / straw tubes endcap silicon strips silicon strips / straw tubes ECAL: barrel crystals (PbWO 4 ) liquid argon / Pb end cap crystals (PbWO 4 ) liquid argon / Pb HCAL: barrel scintillator / brass scintillator / Fe end cap scintillator / brass liquid argon / Cu forward quartz / Fe liquid argon / Cu-W Muon: barrel drift chambers drift tubes +resistive plate +resistive plate end cap cathode strip cathode strip + resistive plate + thin gap ISMD Rohlf p.10/50
ISMD Rohlf p.11/50 HCAL barrel ATLAS: scintillator / Fe CMS: scintillator / brass coverage res. @ 100 GeV thickness η φ ATLAS η < 1.0 8% 8-10 λ front 0.1 0.1 extended barrel 0.8 < η < 1.7 back 0.2 0.1 CMS η < 1.4 10% 11-15 λ 0.087 0.087
ISMD Rohlf p.12/50 HCAL end cap ATLAS: liq. argon / Cu CMS: scintillator / brass coverage res. @ 100 GeV thickness η φ ATLAS 1.5 < η < 3.2 8% 9 λ 1.5 < η < 2.5 0.1 0.1 2.5 < η < 3.2 0.2 0.1 CMS 1.4 < η < 3.0 10% 11 λ 1.4 < η < 1.7 0.087 0.087 1.7 < η < 3.0 0.087 0.17
CMS endcap contribution of Russian Navy ISMD Rohlf p.13/50
ISMD Rohlf p.14/50 Forward ATLAS: liquid argon / Cu-W CMS: quartz / Fe coverage π res. @ 300 GeV thickness η φ ATLAS 3.1 < η < 4.9 8% 9 λ 0.2 0.2 CMS 3.0 < η < 5.0 20% 10 λ 0.17 0.17
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Trigger CMS calorimeter Current Algorithms S. Dasu, University of Wisconsin October 2003-3 ISMD Rohlf p.16/50
ISMD Rohlf p.17/50 Jet Reconstruction C++ code cone based algorithms: SimpleCone IterativeCone MidPointCone (CMS and CDF/DO implementation) cluster algorithms: inclusive KtJets exclusive KtJets (d cut ) exclusive KtJets (N jets )
ISMD Rohlf p.18/50 HLT Jet Resolution Simple cone algorithm with 3 parameters: cone size, seed threshold, minimum jet E T. Small cone contains energetic partons, but larger cone needed to include soft fragmentation which introduces noise. s/e T 0.5 0.45 0.4 0.35 0.3 0.25 0.2 Resolution vs. generated E T R=0.7 R=0.5 η < 1 3.5 < η < 4.5 0.15 0.1 0.05 0 0 20 40 60 80 100120140160180200 s/e T 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0 20 40 60 80 100120140160180200 E T (GeV) E T (GeV) 0.5 R=0.7 R=0.5 1200 1000 800 600 400 200 R=0.5 Mean=83.8 s =18.0 R=0.7 Mean=92.4 s=22.5 0 0 50 100 150 200 250 2 300 ) di-jet mass (GeV/c
Jet rates ISMD Rohlf p.19/50 The jet rates are huge! Rate (Hz) 10 7 10 6 10 5 10 4 10 3 L = 2x10 33 cm -2 s -1 Calibrated Single Jet Single Jet, 95%Eff Calibrated Triple Jet Triple Jet, 95% Eff Calibrated Quad Jet Quad Jet, 95% Eff Rate (Hz) 10 7 10 6 10 5 10 4 10 3 L = 10 34 cm -2 s -1 Calibrated Single Jet Single Jet, 95%Eff Calibrated Triple Jet Triple Jet, 95% Eff Calibrated Quad Jet Quad Jet, 95% Eff 10 2 10 Jets (R=0.5) 10 2 10 Jets (R=0.5) 1 10-1 10-2 0 200 400 600 800 E T (GeV) 1 10-1 10-2 0 200 400 600 800 E T (GeV) Low Lum. trigger threshold (GeV) rate (Hz) 1-jet + 3-jets + 4-jets 570, 210, 87 9 (1-jet + 3-jets + 4-jets) E miss T (150, 75, 60) 93 5 electron jet 16 52 1 inclusive b jets 200 5 inclusive τ jets 93 3
ISMD Rohlf p.20/50 Calibration overview CMS HCAL is a small system (9072 channels)... however, the number of active elements is large 90k tiles for HB/HE/HO, 200k fibers for HF An absolute calibration of 2% for single particles is the goal on day 1 using radioactive sources tied to test beam measurements. Final calibration is likely to come from data. Is this not almost always the case? Tools: mip, ch. hadrons, γ,z+jet, jet-jet, W jet-jet from top,??? Jet energy calibration and dijet mass calibration constitutes a challenge beyond that of single particle response.
Source calibration technique CMS HCAL is calibrated with moving radioactive sources. The technique is described in E. Hazen et. al, Radioactive Source Calibration Technique for the CMS Hadron Calorimeter, Nucl. Inst. and Meth. A 511 (2003) 311. Mean Signal (least counts) 18.5 18.45 18.4 18.35 18.3 18.25 18.2 18.15 Source In Source Out 18.1 0 50 100 150 200 250 300 350 400 450 Time (14 ms) No. of Measurements No. of Measurements 140 120 100 80 60 40 20 100 0 18.2 18.22 18.24 18.26 18.28 18.3 18.32 18.34 18.36 18.38 18.4 80 60 40 20 a) Source In Source Out b) Source In Source Out Mean (ADC counts) 0 1.5 1.525 1.55 1.575 1.6 1.625 1.65 1.675 1.7 Sigma (ADC counts) ISMD Rohlf p.21/50
ISMD Rohlf p.22/50 Source calibration test beam The technique has been tested in the test beam (2002) 128 HB towers 16 layers and repeated with HE and HF (2003 and 2004). Mean Signal (least counts) 15.6 15.5 15.4 15.3 15.2 15.1 15 0 100 200 300 400 500 600 700 800 Time (15.4 ms)
Resolution and linearity CMS ISMD Rohlf p.23/50
ISMD Rohlf p.24/50 Improving jet resolution with tracks Replace energy recorded in calorimeter with track pc where signals are consistent. Add in tracks that are swept out of jet cone by magnet. Response ECAL (cone 0.5) / E tracker 1.2 ECAL hadronic interactions 1 0.8 0.6 0.4 0.2 0 0 20 40 60 80 100 120 P T single particle, GeV Response HCAL (cone 0.5) / E tracker 1.2 1 0.8 0.6 0.4 0.2 ECAL hadronic interactions 0 0 20 40 60 80 100 120 P T single particle, GeV Response HCAL (cone 0.5) / E tracker 1.4 1.2 1 0.8 0.6 0.4 0.2 MIP ECAL 0 0 20 40 60 80 100 120 P T single particle, GeV CMS Note
ISMD Rohlf p.25/50 Improving jet resolution with tracks cont. Jet resolution improved, huge corrections for central jets (about 25% for 50 GeV, η < 0.3), less for forward jets. Jet energy and jet-jet mass scale corrected. Jet res. Jet scale Jet-jet mass jet E T resolution, (%). reco cone 0.5 40 35 30 25 20 15 10 η jet MC 0.3 calo only calo + tracks (all) calo + tracks (out) E T reco/e T MC, cone 0.5 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 η jet MC 0.3 calo only calo + tracks (all) calo + tracks (out) Number of events 450 400 350 300 250 200 150 100 50 calo only MEAN = 0.88 SIGMA = 0.12 calo + tracks MEAN = 1.01 SIGMA = 0.12 5 0 20 40 60 80 100 120 E T MC jet in cone 0.5, GeV 0.4 0 20 40 60 80 100 120 E T MC jet in cone 0.5, GeV 0-0.5 0 0.5 1 1.5 2 2.5 Z mass reco / Z mass MC
ISMD Rohlf p.26/50 MET Resolution η coverage 7-10% low p T hadrons 5% low p T charged tracks 10% minimum bias event 10-15% pileup (low lum.) 13-15% pileup (high lum.) 20% electronic noise 10-12% det. resolution 15% total = 30-35% in 50 GeV MET (t t events)
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SUSY MET+jets 1500 1400 1300 1200 1100 1000 900 800 miss msugra reach in E T + jets final state A 0 = 0, tanβ = 35, µ > 0 g ~ (3000) h(123) 3 years, high lumi (300 fb -1 ) m1/2 (GeV) g ~ (2500) 1 year, high lumi (100 fb -1 ) q ~ (2000) q ~ (2500) g ~ (2000) 1 year, low lumi (10 fb -1 ) Charged LSP g ~ (1500) 1 month, low lumi (1 fb -1 ) 700 600 g ~ (1000) g ~ (500) q ~ (1000) q ~ (1500) q ~ (500) 500 400 300 200 h (114) mass limit 100 0 Chargino Searches at LEP No symmetry breaking 0 500 1000 1500 2000 m 0 (GeV) ISMD Rohlf p.28/50
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MSUGRA Cascade χ 2 χ 1 h χ 1 b b ISMD Rohlf p.30/50
SUSY Reach χ 2 χ 1 h χ 1 b b m 1/2 (GeV / c 2 ) 800 700 600 500 400 Charged LSP χ 2 τ τ 100 fb -1 10 fb -1 A 0 = 0, tanβ = 30, µ > 0 Br (χ 2 χ 1 h) = 50 % χ 2 χ 1 h h(118) h(120) 300 χ 2 χ 1 Z A(800) 200 100 A(500) χchargino 2 χ 1 bb - searches at LEP II h(114) 0 No EWSB 0 200 400 600 800 1000 1200 1400 m 0 (GeV / c 2 ) ISMD Rohlf p.31/50
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ISMD Rohlf p.34/50 Vector boson fusion Forward cal. important! q W/Z W/Z H q W W 1000 800 600 HF noise (2.7 fc/count) h403 Entries 2000 Mean 4.198 RMS 0.8401 q q 400 200 0 0 5 10 15 20 25 30 Single event, time slices 120 pulse height Entries 20 Mean 8.445 RMS 4.038 100 80 60 40 20 0 2 4 6 8 10 12 14 16 18 20 time sample (25 ns) rapidty of tagged jets
Z jet jet ISMD Rohlf p.35/50
JetMET Dijet mass DC04 (R. Harris) ISMD Rohlf p.36/50
ISMD Rohlf p.37/50 Asymptotic freedom CERN jet events 1982 q q q q q q q q
ISMD Rohlf p.38/50 Compositeness cross section gets a term ŝ αλ 2 q q q q
ISMD Rohlf p.39/50 Scattering quarks 1986 q q (1986) demonstrating: 1/r 2 strong force spin 1 gluon pointlike quarks dσ d cos θ α2 s( c ) 2 1 E CM (1 cos θ) 2
ISMD Rohlf p.39/50 Scattering quarks 1986 q q (1986) αau (1913) demonstrating: 1/r 2 strong force spin 1 gluon pointlike quarks dσ d cos θ α2 s( c ) 2 1 E CM (1 cos θ) 2
ISMD Rohlf p.40/50 Scattering quarks 1986 q q (1986) αau (1913)
ISMD Rohlf p.41/50 Pileup is important! 10 33 cm 2 s 1 10 34 cm 2 s 1 10 35 cm 2 s 1
ISMD Rohlf p.42/50 Effect of pilepup Atlas: W jj from top Events / 2 GeV 120 100 80 No pile-up Events / 2 GeV 100 With pile-up = 5.0 GeV 80 = 6.9 GeV 60 60 40 20 40 20 0 25 50 75 100 125 m jj (GeV) 0 25 50 75 100 125 m jj (GeV)
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VIII ISMD Kaysersberg, France, 1977 ISMD Rohlf p.46/50
ISMD Rohlf p.47/50 E260 First calorimeter jet trigger (1977) Field-Feyman fragmentation σ(pp jet)/σ(πp jet) QCD calculation (G. Fox)
XIII ISMD Volendam, 1982 ISMD Rohlf p.48/50
ISMD Rohlf p.49/50 Summary Jets are an important part of LHC physics Higgs, SUSY, compositeness, and the UNKNOWN! Calibration and triggering will be challenging Relating measured jets to parton 4-vectors remains a central issue If we are lucky, we may have an opportunity to do high-mass jet spectroscopy with high statistics... (top is both a calibration tool and a vicious background)
Predictions ISMD Rohlf p.50/50
ISMD Rohlf p.50/50 Predictions The first physics papers from the LHC will be on jets. ISMD XXXVIII? There will be a renewed interest in multiparticle dynamics at the TeV scale!
ISMD Rohlf p.50/50 Predictions The first physics papers from the LHC will be on jets. ISMD XXXVIII? There will be a renewed interest in multiparticle dynamics at the TeV scale! The results will be exciting (worth waiting for)!