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8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 1 B Physics in CMS Silvia Goy López (CIEMAT) For the CMS collaboration LHC2010, October 4 th -9 th.

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Presentation on theme: "8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 1 B Physics in CMS Silvia Goy López (CIEMAT) For the CMS collaboration LHC2010, October 4 th -9 th."— Presentation transcript:

1 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 1 B Physics in CMS Silvia Goy López (CIEMAT) For the CMS collaboration LHC2010, October 4 th -9 th 2010, Split

2 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 2 Outline and references J/ / ψ prompt and non-prompt cross sections in pp collisions at s = 7TeV (CMS PAS BPH-10-002) Upsilon production cross section in pp collisions at s = 7TeV (CMS PAS BPH-10-003) Open beauty production cross section with muons in pp collisions at s = 7TeV (CMS PAS BPH-10- 007) Inclusive b-jet production in pp collisions at s = 7TeV (CMS PAS BPH-10-009)

3 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 3 The CMS detector CMS very well suited for b-physics due to excellent tracking and muon detectors Pixel detector for precise reconstruction for secondary vertexes Excellent tracking efficiency and resolution Muon system with ability to trigger on low p T muons TRACKER MUON DETECTOR

4 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 4 J/ψ and Υ cross sections Theoretical models do not simultaneously describe the cross-section and polarization measurements at Tevatron. New results from LHC at higher energies and wider rapidity ranges can help clarifying the quarkonium production mechanism Non-prompt charmonium production leads to a direct measurement of bb cross section. Measurements at LHC allow testing current theoretical models at high energy and help to validate QCD and PDFs J/ψ and Υ measurements are starting point for dimuon analysis in CMS

5 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 5 Inclusive J/ψ production cross section Selection: Opposite sign muons constrained to vertex (χ 2 cut) with 2.6<M( + - )<3.5 GeV/c 2 Quality cuts: # hits, χ 2 Muon kinematic cuts Tag muon Is the muon identified? Probe track Tracker Muon system J/ Muon reconstruction and trigger efficiency computed from data using tag+probe method (plus MC correction)

6 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 6 Inclusive J/ψ production cross section Acceptance from MC simulation. Dependent on assumed polarization Various polarization scenarios for prompt component Non-prompt component modeled from b-factory experimental results. Yield: Cristal Ball plus exponential in p T bins, in two rapidity ranges. Central region better resolution and low background End-cap region down to p T ~0

7 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 7 Inclusive J/ψ production cross section Total cross section for inclusive J/ψ production 4< p T (J/ψ)< 30 GeV/c, |y(J/ψ)|<2.4 Results for 100 nb -1 Differential vs p T (J/ψ)<30 GeV/c in two rapidity regions Main source of systematic uncertainty from muon efficiency. Will be reduced with additional data

8 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 8 J/ψ prompt vs non-prompt Signed decay length of secondary vertexes Signed impact parameter of tracks in the jet For each candidate estimate B-hadron decay length = l J/ψ = Fraction of J/ψ s from B-hadron decays obtained by ML fit to F(l J/ψ,M( + - )) in p T bins Main source of systematic uncertainty from primary vertex estimation and resolution model for prompt component

9 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 9 Non- Prompt J/ψ prompt vs non-prompt Cross section for J/ψ production due to B-hadron decays 4< p T (J/ψ)<30 GeV/c, |y|<2.4 σ ( J/ψ from B)*BR( J/ψ -> + -)=56.1 ± 5.5 (stat) ± 7.2 (syst) nb Prompt 2< p T (J/ψ)<4 GeV/c, 1.4<|y|<2.4

10 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 10 Theoretical predictions for Y more robust than for charmonium due to heavier b quark Selection similar to J/ψ Kinematic cuts Efficiencies computed using T&P technique on J/ψ sample, reweighing for different p T distribution Acceptance and efficiencies in p T ( ), η ( ) bins applied event by event. Upsilon production cross section Signal extraction EUML fit to mass distribution in p T (Υ) bins to 3Crystal ball +linear function for background Common resolution for 3 peaks Y(1S) mass free parameter, ΔM of the others fixed by PDG

11 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 11 Upsilon production cross section Results for 280 nb-1 of data, assuming zero polarization Main source of systematic uncertainty in Y(1S) production cross section is determination of muon identification efficiency (will be reduced with additional data) and luminosity.

12 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 12 b-production Recent progress in theoretical understanding of b-quark production (in particular fragmentation) but theoretical uncertainties still sizeable Big interest in verifying the results at LHC energies, high cross section for bb production, accessing new regions in phase space. In addition events containing b-quarks are important background for many searches. Two methods for measuring inclusive b-production cross section, with different kinematic reaches and systematic uncertainties: Muon tagging Jet tagging b-production at LHC

13 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 13 b-production with muons In semileptonic decay of b-quarks into muons and jets, the transverse momentum of the muon wrt closest track jet discriminates b events from background Tracks clustered in jets with anti-kT with R=0.5 Binned log-likelihood fit of the observed p T rel to obtain f b from data Signal and c-template from simulation udsg background dominated by hadrons misidentified as muons, determined from data

14 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 14 b-production with muons Trigger efficiency (single muon trigger) from data with minimum bias events. Muon reconstruction efficiency, b-jet finding efficiency, fake rate from simulation. Systematic uncertainties dominated by description of the udsg background and of the underlying event and by luminosity Lumi=8.1 nb -1

15 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 15 b-production with jet b-tagging Signed decay length of secondary vertexes Signed impact parameter of tracks in the jet Secondary vertices (SV) from b- and c/light-quark decays can be distinguished by their relative distance from the primary vertex using a 3D decay length significance Reconstruct PF jets in 18<p T <300 GeV with anti-kT in R=0.5, with |y|<2.0 b-jets identified with secondary vertex tagger

16 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 16 b-production with jet b-tagging N tagged = Measured number of tagged jets per (p T,η) bin. f b = fraction of tagged jets containing a b-hadron (purity) ε b = efficiency of tagging b-jets ε jet = jet reconstruction efficiency C smear =unfolding correction from measured p T back to particle level f b, ε b, ε jet calculated from MC in (p T,η) bins, in agreement with data estimations. 18<pT<300 GeV, |y|<2.0

17 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 17 b-tagging efficiency Pass b-tag Fail b-tag Efficiency of tagging b-jets from simulation. Measured in the data using semileptonic decays of b-> +jets. Fit p T rel both in b-tagged and in non b- tagged sample. Efficiency given by ratio of corresponding Nb Data/MC ratio: 1 within 20% statistical uncertainty.

18 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 18 b-tagging purity Data estimate: Compute invariant mass of tracks associated to SV computed after selection. Fit performed, taking shapes for light, c, b from simulation. Good data/MC agreement

19 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 19 Inclusive b production with b-tagging Leading uncertainties: jet energy scale, luminosity, b-tag efficiency and mistag rates.

20 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 20 Ratio b-jet to inclusive jet production Luminosity and jet energy scale uncertainties cancel out in the ratio Leading uncertainties from b-tag efficiency and charm mistag rates. These are statistical uncertainties from data-driven methods.

21 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 21 Conclusions Very good tracking and muon detector performance allow rich quarkonia and B-Physics program at CMS. First measurements of J/ψ and Y cross sections at 7 TeV available. Very good b-tagging performance from early stage already! Measurement of inclusive b-production cross section has been possible with this method And much more to come!

22 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 22 Main references CMS PAS BPH-10-002. J/ / ψ prompt and non-prompt cross sections in pp collisions at s = 7TeV CMS PAS BPH-10-003. Upsilon production cross section in pp collisions at s = 7TeV CMS PAS BPH-10-007. Open beauty production cross section with muons in pp collisions at s = 7TeV CMS PAS BPH-10-009. Inclusive b-jet production in pp collisions at s = 7TeV CMS PAS BTV-10-001. Commissioning of b-jet identification with pp collisions at s = 7TeV CMS PAS MUO-10-002. Performance of muon identification in pp collisions at s = 7TeV CMS PAS TRK-10-002 Measurement of tracking efficiency. CMS PAS JME-10-001. Jets in 0.9 and 2.36 TeV collisions

23 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 23 Back Up

24 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 24 First exclusive B channels

25 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 25 b-tagging input variables Data/MC

26 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 26 b-tagging

27 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 27 b-tagging

28 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 28 b-tagging

29 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 29 b-tagging

30 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 30 Negative tags

31 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 31 Templates for b-tagging efficiency

32 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 32 b-tagging, production mechanism

33 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 33 J/Psi

34 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 34 Ks mass

35 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 35 J/Psi mass

36 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 36 J/Psi mass

37 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 37 J/Psi mass

38 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 38 J/Psi: muon momentum resolution

39 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 39 Upsilon

40 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 40 Muon ID efficiency

41 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 41 Single muon trigger eff

42 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 42 Muon ID and trigger efficiencies

43 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 43 Systematics J/psi yield

44 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 44 Systematics non-prompt J/psi yield

45 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 45 Systematics upsilon yield

46 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 46 Systematics open beauty

47 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 47 PV

48 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 48 PV

49 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 49 Material budget

50 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 50 Muon: fakes and efficiencies

51 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 51 Muons in jets

52 8/10/2010 LHC Days, Split Silvia Goy Lopez (CIEMAT) 52 JEC

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