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b and c production in CMS and ATLAS

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Presentation on theme: "b and c production in CMS and ATLAS"— Presentation transcript:

1 b and c production in CMS and ATLAS
Francesco Fiori on behalf of CMS and ATLAS collaborations VII Meeting on B-physics (LAL)

2 LHC luminosity evolution
LHC startup in March 2010 9.67 pb-1 delivered lumi 5 pb-1 certified lumi 6 pb-1 in the last 2 weeks Inst. lumi > cm-2s-1 Now up to ~ 500 nb-1/day No explosions so far  30/06/2019 F.Fiori

3 b and c LHC The study of heavy quark production is of main interest in LHC: Quarkonia production (J/psi, Y) Test of QCD (NRQCD) CP violation (B-mesons) Higgs (if light enough) Huge programme (already started): Quarkonia and b cross section (already in place) Charmed mesons properties ( pb-1) Quarkonia polarization B-mesons properties (limits to) BR of rare decays (FCNC) ( > 1 fb-1) Need of high performance tracking detectors (b-tagging) and efficient lepton triggers Bs→J/ψ φ candidate in CMS 30/06/2019 F.Fiori

4 CMS and ATLAS Performant inner tracking detectors (based on Si pixels and strips) Fast and redundant muon identification system (Mu triggers) Extended coverage with respect to Tevatron detectors (|η|≤ 2.5) Very different configuration of B field, in the inner region superconducting solenoids are used by both (2 vs 4 T) 3 Levels for trigger decision (L1 Hardware, L2/L3 software) 30/06/2019 F.Fiori

5 J/ψ Very inclusive trigger paths: ATLAS: MinBias + L1 single Muon
Fit : /- 345 Mean : GeV +/ Very inclusive trigger paths: ATLAS: MinBias + L1 single Muon CMS: L1 Double Muon + single Mu (pT>3 GeV/c) Pairs of opposite charge muons Good primary vertex and secondary vertex by the two muons Quality cuts (n° of hits, χ2 fit ... See backup) Yields extracted by MLL fits to data: CMS: CB + Exp ATLAS: Gauss + Linear 30/06/2019 F.Fiori

6 Cross Section from MC From data , T&P (for CMS) From fit to data (MLL)
ATLAS weights event by event with 1/Aε (efficiency taken by simulation) CMS correct the yields in each bin with 1/<A ε> The acceptance is strongly dependent by the polarization, 5 scenarios considered: ATLAS include in systematic error , CMS quotes 5 Xsections 30/06/2019 F.Fiori isotropic Helicity fully long. Collins-Soper fully long.

7 Differential Cross Section
Systematics: Signal (background) PDF (1-8%) Single Mu efficiencies (10-15%) Momentum scale (>1%) FSR (1-2%) Polarization (not included in sys.) Total production cross section in 4 < pT<30 and |y| <2.4: 289.1 ±16.7(stat) ±60.1(syst) nb For details on J/psi see: ATLAS CMS 30/06/2019 F.Fiori

8 B-Fraction pseudo-proper decay length
Prompt J/ψ: triple Gaussian resolution function Simultaneus MLL fit to the mass and lifetime distributions B-hadron component, two approaches: MC template of true pseudo-decay length, convoluted with the same resolution function extracted from prompt decays (used as reference) Assume a convolution of an exponential decay with two resolution functions: A Boost resolution function to account for differences between the B-hadron and the J/Psi boost Decay length resolution R (assumed to be the same of prompt J/Psi) (The difference is taken as systematic) 30/06/2019 F.Fiori

9 Lifetime Fits 56.1±5.5(stat)±7.2(syst) nb Resolution: Barrel
pT   (85 ± 15) um pT   (46 ± 5) um pT (39 ± 7) um Forward pT   (253 ± 9) um pT   (141 ± 6) um pT   (74 ± 4) um pT (55 ± 4) um pT (37 ± 6) um 0<pT<2 forward 2<pT<4 forward Total cross secion x Br for B hadron decays in 4< pT< 30 and|y|<2.4: 56.1±5.5(stat)±7.2(syst) nb 30/06/2019 F.Fiori

10 Comparison with predictions
prompt Non prompt 30/06/2019 F.Fiori

11 ... and with other experiments
compilation by Hermine Woehri 30/06/2019 F.Fiori

12 Ψ(2S) R= N(psi(2S))/N(J/psi):
Resolution J/psi: 20 MeV +/- 0.6 Mean J/psi: GeV +/ N psi(2S): 311 +/- 23 Resolution psi(2S): 18 MeV +/- 2 Mean psi(2S): GeV +/ CDF R= N(psi(2S))/N(J/psi): RCMS = ± (<pT>=11.7 GeV/c) RATLAS = ± 0.005 30/06/2019 F.Fiori

13 Y family Y family well visible in CMS and ATLAS data
NY(1S) = 678 ± 38 NY(2S) = 158 ± 24 NY(3S) = 81 ± 21 Y family well visible in CMS and ATLAS data CMS already published a pT differential cross section The selection of events is the same of the J/psi 30/06/2019 F.Fiori

14 Y production in CMS Trigger: Double Muon at L1 Fit: 3 Gaussians + Linear Dominant source of systematics is the efficiency computation (statistical origin) Barrel only Full Stat. 5 cross sections quoted for the different polarizations Stat Lumi sys. R= [σ(Y2S) + σ(Y3S)]/σ(Y1S) Deatails here 30/06/2019 F.Fiori

15 B±-mesons in CMS Single Mu trigger (pT> 3GeV/c)
Opposite sign di-muon combinations, if more than one chose the one with mass closest to the J/psi mass di-muon vertex Probability >0.1% Combine J/psi candidate with tracks (pT>0.9 GeV/c) Kinematic fit with J/psi mass constraint Require vertex probability > 0.1% If multiple candidates/event, choose highest pT B- candidate cτ(J/ψK)/Δcτ > 1 N_sig= 48 ± 8 Mean= GeV/c2 Resolution= 32 MeV/c2 Details here 30/06/2019 F.Fiori

16 Inclusive b-jet production in CMS
CMS measured a double differential cross section for b-jet production and the ratio to inclusive jet production in the kinematic range |y|<2 and 18 < JpT < 300 GeV/c b-tag: The secondary vertex is fitted with at least three charged particle tracks. A selection on the reconstructed 3D decay length significance is applied, corresponding to about 0.1% efficiency to tag light flavor jets and 60% efficiency to tag b jets at pT = 100 GeV. Purity and mistag probability taken from MC (Pythia) Trigger: MinBias + single-jet 30/06/2019 F.Fiori

17 b-jets/inclusive-jets
The ratio reduces the uncertainties on JES and luminosity Good agreement with Pythia NLO calculations are in agreement at low pT, with very different shape at high pT Leading systematics: b-tagging efficiency (20%) Mistag (1-10%) Details here 30/06/2019 F.Fiori

18 Conclusions After 6 months from the LHC start up ATLAS and CMS have produced good quality physics results New results with much more statistics coming soon (weeks) J/psi X section measurement in place for both experiments More refined B-physics studies require more data however the collaborations seem very reactive. The re-discovery of the Standard Model is just started 30/06/2019 F.Fiori

19 Back up 30/06/2019 F.Fiori

20 Selection I Event selection: Mu selection: Triggers used:
Good Vertex, Anti Scraping [+L1 tech bits (only for runs<136086)] Mu selection: Use GlobalMuons and TrackerMuons see next slide for selection details No Mu cleaning (does not affect x-section once using trigger bits) Triggers used: HLT_L1DoubleMuOpen (pT<4 GeV/c) + HLT_Mu3 (pT>4 GeV/c) strategy: keep the loosest unprescaled trigger path and that gives the smallest systematics Analysis is performed on GG+GT+TT In case more than a combination use the GG; if both are GG, GT or TT take the one with larger pT Given the small number of events the three categories are lumped into a single category. 30/06/2019 F.Fiori

21 Selection II Both muons in acceptance Muon tracker tracks:
χ2/ndof < 4.0 |d0| < 3.0 cm (calculated w.r.t. PV) |dz| < 15.0 cm (calculated w.r.t. PV) number of valid hits (pixel + strips) > 11 number of pixel layers with hits ≥ 2 Global muons: χ2/ndof (global fit) < 20.0 number of valid muon hits > 0 also tracker muons arbitrated and passing TMLastStationAngTight selector Tracker muons: arbitrated and passing TMLastStationAngTight a secondary vertex must be found with P(χ2) > 0.1% 30/06/2019 F.Fiori

22 Mass Fit CB signal + Exponential background
Example of two (very) different bins: Practically no background High background level, worse resolution Fit : 923 +/- 59 Resolution : /- 2.4 MeV/c2 Mean : / GeV/c2 S/B= 1.4 Fit : 412 +/- 22 Resolution : /- 1.4 MeV/c2 Mean : / GeV/c2 S/B= 26.5 1.4 <|y|<2.4 0 < pT < 1 |y|<1.4 8 < pT < 10 L1DoubleMuOpen HLT_Mu3 we have considered a CB+Gauss for the signal and a linear fit for the background to estimate for systematics 30/06/2019 F.Fiori

23 Efficiencies From single mu to J/ψ: Triggers used:
Determined by T&P (single muon) From single mu to J/ψ: From data For double Mu trigger All the single muon efficiency computed on data For single Mu trigger Triggers used: L1DoubleMuOpen (Forward region for pT<4 GeV/c) HLT_Mu3 (For pT>4 GeV/c, gives a better S/B) 30/06/2019 F.Fiori

24 Trigger efficiency (T&P)
DoubleMuOpen HLT_Mu3 30/06/2019 F.Fiori

25 Id and Tracking Muon Id Tracking: use the T&P from PAS TRK-10-002.
assumed that the pT behaviour is the same between the data and MC. Correct for phi-eta dependence. 30/06/2019 F.Fiori

26 Inclusive Xsection As the data sample grows, it will become possible to measure the polarization and re-evaluate the corresponding cross section. 30/06/2019 F.Fiori

27 B-tagging efficiency 30/06/2019 F.Fiori

28 Purity 30/06/2019 F.Fiori

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