Heavy flavor produc.on and spectroscopy at ATLAS. For the ATLAS collabora.on

Transcription

1 Heavy flavor produc.on and spectroscopy at ATLAS Brad Abbo8 University of Oklahoma For the ATLAS collabora.on 1

2 Introduc.on Charmonium/Open Charm Produc2on Measurement of the differen.al cross- sec.ons of prompt and non- prompt produc.on of J/ψ and ψ(2s) in pp collisions at s = 7 and 8 TeV with the ATLAS detector, arxiv: (To appear in EPJC) ± ± ± Measurement of D*, D and D s meson produc.on cross sec.ons in pp collisions at s=7 TeV with the ATLAS detector, arxiv: (To appear in Nucl. Phys. B) B Baryons/B c Measurement of the branching ra.o Γ(Λ 0 b J /ψλ 0 ) with the ATLAS detector, arxiv: (Phys Le8 B 751 (2015) 63-80) Study of the B + + c J /ψ D s and B + *+ c J /ψd s decays with the ATLAS detector, arxiv: (Eur. Phys J.C, 76(1), 1 (2016)) b Quark Fragmenta2on Determina.on of the ra.o of b- quark fragmenta.on frac.ons f s /f d in pp collisions at s=7 TeV with the ATLAS detector, arxiv: (PRL 115, (2015)) 13 TeV Results ± ± ± ( ) Γ Λ b 0 ψ(2s)λ 0 B mass reconstruc.on in B J/ψ K decay at ATLAS at 13 TeV pp collisions at the LHC, ATLAS- conf Differen.al non- prompt J/ψ produc.on frac.on at s= 13 TeV,ATLAS- conf All ATLAS Heavy Flavor results can be found at: h8ps://twiki.cern.ch/twiki/bin/view/atlaspublic/bphyspublicresults 2

3 Muon Spectrometer Triggering η <2.4 Precision Tracking η <2.7 ATLAS Experiment Inner Detector PT>0.4 GeV η <2.5 New for Run2: Insertable B- Layer (IBL) Addi.onal inner- most pixel layer (r=33mm) and lower x/x0 beam pipe Resolu.on in mµ+µ- ~50 MeV for J/ψ and 150 MeV for ϒ(nS) Resolu.on in b- hadron proper decay.me ~100 fs (no IBL, ~30% improvement expected 3

4 Data Datasets (pp): 7 TeV data, 5.08 p ns bunch spacing Peak: 3.7 x cm - 2 s TeV data, 21.3 p ns bunch spacing Peak: 7.7 x cm - 2 s TeV data, 3.9 p /25 ns bunch spacing Peak: 5.0 x cm - 2 s - 1 4

5 Triggering for Heavy Flavor physics 20/40 MHz collision rate ~400 Hz recorded HF physics concentrates on low p T di- muon signatures Quarkonia : J/ψ µµ, ϒ µµ Exclusive: B J/ψ(µµ) X decays Rare decays: B µµ(x) decays Trigger on low- p T 4,6 GeV dimuons Large gain in yields w.r.t single muon triggers 5

6 Charmonium Produc.on at the LHC Quarkonium produc.on at the LHC offers unique windows on our understanding of the strong interac.on Two dis.nct charmonium produc.on mechanisms at the LHC Prompt: Produced directly in the pp interac.on or through feed- down from heavier (directly produced) states Theory: Non- rela.vis.c QCD Non- Prompt: produced in decays of b- hadrons, can be separated experimentally due to the long b- hadron life.me. Theory: Fixed Order Next- to- Leading Logarithm ~35% of prompt J/ψ come from feed- down, ψ(2s) are almost all direct 6

7 J/ψ and ψ(2s) Produc.on at 7 and 8 TeV Data (2.1 p - 1 at 7 TeV and 11.4 p - 1 at 8 TeV) collected with dimuon triggers, basic muon kinema.c selec.on (P T (µ 1,2 )>4 GeV and η(µ 1,2 ) <2.3) and vertex fit of dimuon tracks Each dimuon candidate is weighted to correct for trigger efficiency, muon iden.fica.on, and reconstruc.on and geometrical acceptance. Corrected prompt and non- prompt J/ψ and ψ(2s) yields are determined from an unbinned fit to the 2- D dimuon mass and pseudo- proper decay.me (τ) distribu.on τ = L xym(j /ψ) 2- D fits performed in 22 p T x 8 rapidity bins p T (J /ψ) 7

8 J/ψ and ψ(2s) Produc.on at 7 and 8 TeV Prompt J/ψ compared to NRQCD- good agreement across range of P T, no y dependence 8

9 J/ψ and ψ(2s) Produc.on at 7 and 8 TeV Prompt ψ(2s) (no significant feed- down) compared to NRQCD. Generally describes data well but deteriorates at higher p T 9

10 J/ψ and ψ(2s) Produc.on at 7 and 8 TeV Non- prompt compared to FONLL- predicts slightly harder p T spectra Seen consistently across charmonium, open charm and open beauty measurements compared to FONLL J/ψ ψ(2s) 10

11 J/ψ and ψ(2s) Produc.on at 7 and 8 TeV Ra.o of ψ(2s)/j/ψ Prompt: slight increase as func.on of p T Non- prompt: consistent with flat across the whole p T range studied Prompt J/ψ frac.on dominates at low p T but non- prompt exceeds prompt at ~20 GeV 11

12 D* produc.on Charm produc.on studied through the reconstruc.on of exclusive D meson decays D* ± D ± ± D s D + φπ + (φ K + K - ) Valuable tool for tuning and valida.on of MC generators used for LHC physics Total and differen.al cross sec.ons compared to a range of theory predic.ons and MC generators Results within fiducial space (3.5<P T <100 GeV, η <2.1) extrapolated to a measurement of the total charm cross sec.on tot σ cc = 8.6 ± 0.3(stat) ± 0.7(syst) ± 0.3(lum) ± 0.2( ff ) (extr)mb ff fragmenta.on func.on extr extrapola.on procedure 12

13 D* +- D +- Extracted strangeness suppression factor in charm fragmenta.on 0.26 ± 0.05(stat) ± 0.02(syst) ± 0.02(br) ± 0.01(extr) Extracted frac.on of charged non- strange D- mesons produced in a vector state 0.56 ± 0.03(stat) ± 0.01(syst) ± 0.01(br) ± 0.02(extr) 13

14 B- quark Fragmenta.on Frac.ons f s /f d Important for studies such as B (s) µµ Using decay modes B s J/ψφ and B 0 J/ψ K *0 f s f d B(B 0 s J /ψφ) B(B 0 d J /ψk *0 ) = ± 0.004(stat) ± 0.008(syst) Perturba.ve QCD predic.on X. Liu, W. Wang, Y. Xie: Phys. Rev. D 89 (2014) , arxiv: v2 B(B 0 s J /ψφ) B(B 0 d J /ψk *0 ) = (ω B ) ( f M ) (a i ) (m c ) f s f d = ± 0.004(stat) ± 0.010(syst) ± 0.017(th) 14

15 B- quark Fragmenta.on Frac.ons f s /f d Measured as a func.on of p T and η (no evidence of dependence found) 15

16 Observa.on of Λ b ψ(2s)λ First observa.on of the decay mode Λ b Measured rela.ve BR to Λ b J/ψ Λ 0 ψ(2s)λ (8 TeV pp collisions) In kinema.c range p T (Λ b ) > 10 GeV and η(λ b ) <2.1 Modeling B 0 ψ(ns)k 0 s reflec.on < 0.5% bias to ra.o from Λ b Λ 0 µµ Γ(Λ b 0 ψ(2s)λ 0 ) Γ(Λ b 0 J /ψλ 0 ) = 0.501± 0.033(stat) ± 0.016(syst) ± 0.011(Br) Predic.on: 0.8 ± 0.1 ** in analogous B meson decays 16 ** T. Gutsche et. al. PRD 88 (2013)

17 BR and Angular Analysis of B c J/ψ D S +(*) Two heavy quarks, both can decay weakly, affects theore.cal predic.on of B c proper.es B c J/ψ D +* s decay is a transi.on of PS V+V described by 3 helicity amplitudes Simplified angular analysis, dis.nguishing A 00 from (A ++ and A - - ) ±± Measuring frac.on of transverse polariza.on Γ /Γ 00 Measurement of rela.ve BR of B c J/ψ D s + w.r.t B c J/ψ D s +* and of both the decay modes w.r.t BR of B c J/ψ π + D s + φ(k + K - )π + D s +* D s+ [π 0 /γ] soy (not detected) MC based templates 17

18 B c J/ψ D S +(*) Results B Bc + J /ψd s + B Bc + J /ψπ + = 3.8 ±1.1(stat) ± 0.4(syst) ± 0.2(BF) Ra.os of BR B Bc + J /ψd s *+ B Bc + J /ψπ + =10.4 ± 3.1(stat) ±1.5(syst) ± 0.6(BF) B Bc + J /ψd s *+ B Bc + J /ψd s + = (stat) ± 0.3(syst) Transverse polariza.on frac.on Γ ±± Γ = 0.38 ± 0.23(stat) ± 0.07(syst) Comparison to LHCb and Theore.cal predic.ons 18

19 Measurement of B + mass with 13 TeV data Ini.al performance study using full (3.2 p - 1 ) 2015 pp dataset at s= 13 TeV in prepara.on for further detailed b- hadron measurements ± ± Reconstruct B J/ψ K decay with simple selec.on P Tµ > 4GeV and P K T > 3 GeV Perform three- track (µ + µ - ± K ) vertex fit with χ 2 /dof<3 ± B mass extracted from 16 separate unbinned fits to ± ± M(J/ψ K ) distribu.ons binned in y(j/ψ K ) Systema.c uncertainty (0.25 MeV) dominated by fit model (momentum scale not yet included) Fit B ± mass [MeV] Fit error [MeV] Default Fit (stat.) L xy > 0.2 mm (stat.) World Average fit LHCb (stat.) ± 0.33 (syst.) Good agreement with world average 19

20 Non Prompt J/ψ frac.on at 13 TeV First ATLAS quarkonium produc.on measurement at 13 TeV. Similar to Run- 1 study Early data sample of 6.4 pb - 1 collected with di- muon triggers Yields extracted from an un- weighted and unbinned fit to 2D dimuon mass and pseudo proper decay.me Efficiencies and acceptance cancel to a good approxima.on in the non- prompt frac.on. Assign small (3%) uncertainty Li8le dependence on s when moving from 7 to 13 GeV Minimal dependence on rapidity, similar to Run- 1 results 20

21 Conclusions Number of new results in produc.on and decay proper.es using full Run- 1 data set. Important input for theory MC generator tuning First studies of 2015 pp collision data at s=13 TeV. J/ψ produc.on and b- hadron reconstruc.on ATLAS will con.nue its B- physics program in Run 2,3 and the HL LHC era. Focusing on precision measurements, rare decays and heavy flavor produc.on and spectroscopy. Detector upgrades (tracking and muon system) and new trigger strategies will help to cope with high luminosity environment 21