LHCb Physics, Performance, Prospects

Transcription

1 7th Patra Workhop Mykono, June 26-July 1, 211 LHCb Phyic, Performance, Propect Olaf Steinkamp on behalf of the LHCb collaboration Phyik-Intitut der Univerität Zürich Winterthurertrae 19 CH-857 Zürich

2 Short phyic motivation Brief introduction to the LHCb experiment Some word on operational experience A few elected reult from 21 data taking Outlook for 211 and beyond

3 CKM Matrix and Unitarity Triangle quark mixing in charged-current interaction L cc = g 2 2 u i γ μ ( 1 γ 5 ) V ij d j Wμ V ij = 3 quark familie 4 independent parameter ( V ud V u V ub V cd V c V cb V td V t V tb ) 3 rotation angle + 1 complex phae ource of all CP violation in Standard Model unitarity implie 6 orthogonality condition 6 unitarity triangle in complex plane Vud V ub V cd V cb THE Unitarity Triangle from 1t and 3rd row: V ud V ub V cd V cb V td V tb = ( ρ,η ) α γ (, ) Vtd V tb V cd V cb β (1, ) ide and angle of Unitarity Triangle can be preciely determined from variou obervable in B meon ytem: B+ =(u b), B(d) =(db), B =( b) + cc LHCb Phyic, Performance, Propect (3/28)

4 Unitarity Triangle from B decay many obervable (jut howing ome of the more intereting one): BF(B π ℓ ν ℓ ) BF(B D ℓ ν ℓ ), CP violation in B d π π,ρρ,ρ π BF (B Xu ℓ ν ℓ ) BF (B X c ℓ ν ℓ ) BF(B± τ ± ν τ ) ( ρ, η ) B d B d and B B ocillation frequencie α CP violation in B± DK±, B D K, γ (, ) CP violation in β (1, ) B d J/ ψ K, B d ϕ K over-contrained determination of Unitarity Triangle inconitencie would be ign for New Phyic beyond the Standard Model pattern of deviation can hint at underlying dynamic of the New Phyic LHCb Phyic, Performance, Propect (4/28)

5 Statu 21 many beautiful meaurement at B factorie (BaBar, Belle) and Tevatron (CDF, DO) all reult conitent with Standard Model prediction CKM dominant ource of CP violation in quark ector meaurement preciion permit Box Diagram New Phyic at ~1% level loop-mediated procee: new heavy particle can B potential for indirect dicovery of new particle to mae far in exce of LHC energy W b change amplitude and phae u,c,t ± u,c,t B b? Penguin b b B W ± u,c,t B b b B LHCb Phyic, Performance, Propect (5/28) + K u B u K? + K u u K

6 LHCb Phyic Programme main goal: perform preciion meaurement of CP violating phae and rare heavy-quark decay pecial emphai on obervable with large enitivity to New Phyic improve conitency tet of Unitarity Triangle compare procee with different enitivity to New Phyic B B mixing phae, rare B decay exploit the large b b production cro ection at the LHC from Penguin & from Tree obervable that are predicted to be mall in the Standard Model preciion on CKM angle 29 μb at 7 TeV v. 1 μb at Tevatron v. 1 nb at B factorie dedicated etup, fully optimized for it phyic programme LHCb Phyic, Performance, Propect (6/28)

7 Forward Spectrometer CMS cover forward region ( 1.9 < η < 4.9 ) optimized for the trongly forward peaked LHCb heavy quark production at the LHC cover only ~4% of olid angle but capture ~4% of heavy-quark production cro ection LHCb Phyic, Performance, Propect (7/28)

8 Key Feature excellent vertex and proper-time reolution econdary B decay vertex rapid B B ocillation excellent momentum and invariant ma reolution background rejection excellent kaon/pion eparation final tate with kaon/pion flavour tagging efficient trigger on hadron a well a muon and electron purely hadronic final tate LHCb Phyic, Performance, Propect (8/28)

9 LHCb Detector VErtex LOcator muon ytem RICH detector interaction point tracking ytem calorimeter LHCb Phyic, Performance, Propect (9/28)

10 Optimized Trigger overcome large inelatic cro ection: >1 x bb cro ection elect intereting B decay channel: typical branching fraction of 1-5 exploit generic B decay ignature: decay product with large p T (few GeV) _ and high impact-parameter, well eparated B decay vertex high-et cluter (e,h,γ) in calorimeter Software level (HLT): multi-proceor farm (14k core) acce to full detector data HLT1: cut on impact parameter and lifetime HLT2: global event recontruction + election for pecific channel L e, L had L 1 MHz HLT1 high-pt μ track egment in muon ytem Impact Parameter Lifetime cut 3 khz Global recontruction HLT2 High-Level Trigger Hardware level (L): Level - 4 MHz Incluive election, +track, Excluive election 2 khz LHCb Phyic, Performance, Propect (1/28)

11 Data Taking LHCb fully operational from firt day of LHC colliion in March 21 > 9% of detector channel operational data taking efficiency > 9% cap intantaneou luminoity to keep fraction of event with multiple pp interaction mall track multiplicity in buy forward region aignment of B decay to primary vertex luminoity levelling by teering of LHC beam operating uccefully at ignificantly higher pp interaction per LHC bunch croing colliion multiplicitie than foreeen in deign nominal now (preliminary) reult hown here baed on ~ 35 pb-1 of data collected in 21 already collected ~ 3 pb-1 in 211 expect 1 fb-1 by the end of the year LHCb Phyic, Performance, Propect (11/28)

12 Charged Particle Tracking ilicon micro-trip uptream of magnet traw + ilicon micro-trip downtream bigget challenge i patial alignment no detector inide magnet no acceptance for comic meaured reolution very cloe to imulation J/, , 2, 3 LHCb Phyic, Performance, Propect (12/28)

13 b J/ X Signal B J/ K b J / B J/ K B J / clean ignal, excellent ma reolution c.f. CMS: ~ 16 MeV, ATLAS: ~ 26 MeV world' bet ma meaurement [LHCb-CONF ] preliminary LHCb Phyic, Performance, Propect (13/28)

14 Vertex Recontruction ilicon trip detector inide LHC vacuum pipe only 8mm from LHC beam during data taking retracted by ±3 cm in between fill internal alignment better than 5 μm proper-time reolution t 5 f 6 cm compare to B lifetime: B 15 f meaured lifetime compatible with PDG value B+ J / ψ K+ [LHCb-CONF-211-1] preliminary LHCb Phyic, Performance, Propect (14/28)

15 K/ Identification B flavour tagging down to few GeV two-body B decay up to 1 GeV ± ± ± B d π π B(d, ) K π B K K two RICH detector with three radiator photon-detection in pixel-hpd performance cloe to imulation for all momenta GeV/c GeV/c LHCb Phyic, Performance, Propect (15/28)

16 B h h' Signal + - B h+ h ' 2-body decay, no PID, π ma aumed for both decay particle apply PID cut B B K±, B K± LHCb Phyic, Performance, Propect (16/28) B K K

17 CP Violation in B K π ± further eparate B K± π ample into B K+ π and B K π+ aymmetry in ignal yield how CP Violation B K π + + after correction for (mall) production and detection aymmetrie: ACP ( B K + π ) =.74±.33±.8 B K π in good agreement with world average: [LHCb-CONF ] preliminary ACP ( B K + π ) = [HFAG 21] charmle two-body B-decay mode central to LHCb phyic programme ignificant contribution of Penguin diagram window to New Phyic! LHCb Phyic, Performance, Propect (17/28)

18 _ bb Production Cro Section from B D(K-π +) μ -X+: identify D from B by large impact parameter with repect to D from B recontructed primary vertex ue wrong-ign D μ pair to etimate background prompt D - fake from B J/ψ X: ue ditribution of peudo proper time tz to identify J/ from b extrapolate from LHCb acceptance to full phae pace: Pythia Monte-Carlo σ (pp b b X) = (284±2±49) μ b [Phy Lett B 694 (21) 29] σ (pp bb X) = (288±4±48) μ b [Eur Phy J C71 (211) 1645] good new: LHCb performance imulation had aumed 25 μb at 7 TeV LHCb Phyic, Performance, Propect (18/28)

19 CKM angle mot poorly meaured angle of the Unitarity Triangle γ can be determined from pure Tree procee and from Penguin procee improving meaurement preciion tet conitency of Unitarity Triangle comparion of reult probe poible New Phyic contribution in Penguin LHCb: for both approache expect σ(γ) ~ 5º with 211/12 data LHCb Phyic, Performance, Propect (19/28)

20 from Tree D K B e f K D K B b c u u K V ub e B D f u D f c b iγ u u K _ u iγ final tate f common to D and D interference of tree amplitude with different weak phae lead to different decay rate for B+ and B- decay f = KK, ππ ; f = K+π - ; f = Kππ variou decay rate ratio and aymmetrie B± D (K π )K± enough obervable to extract γ, trong phae, ratio of magnitude between the two diagram but: interference mall, branching ratio mall tatitic from Tevatron/B factorie inufficient advantage LHCb: large B production rate, example B D (K π )K LHCb: ~44 event from.35 fb-1 CDF: ~15 event from 5 fb-1 ± ± efficient trigger for hadronic final tate, excellent K/π identification LHCb Phyic, Performance, Propect (2/28)

21 from Penguin B e e π π (K K ) + i2β() B () e i γ + B b V ub e i γ + K u u K b B u K Penguin ignificant New Phyic enitivity! meaure two time-dependent CP aymmetrie ACP (t) = Amix in(δ m( d, ) t) + Adir co(δ m( d, ) t) + u K CP violation from interference of mixing and decay () iγ B d π + π aume U-pin ymmetry (exchange of d quark) Penguin/Tree ratio the ame for both channel take mixing phae β () from B d J/ ψ K, B J / ψ ϕ extract γ together with Penguin/Tree ratio (phae and magnitude) from the four amplitude B K K LHCb advantage: a before + excellent proper time reolution to reolve fat B B ocillation LHCb Phyic, Performance, Propect (21/28)

22 B B Ocillation Frequency meaured uing flavour-pecific decay B D (3)π + with D K+ K π total of ~ 13 ignal event from 35 pb-1 flavour at production ( B or B ) implied from combination of oppoite-ide tagger lepton charge kaon charge vertex charge calibrated on B+ J / ψ K+ and B d D π + reult competitive with previou world-bet meaurement from CDF (uing 1 pb-1) Δ m = ( ±.11(tat) ±.4 (yt) ) p 1 Δ m = ( ±.1 (tat) ±.7 (yt) ) p [LHCb-CONF-211-5] preliminary [PRL 97, ] LHCb Phyic, Performance, Propect (22/28)

23 B B Mixing Phae ϕ = 2β B e i2β J/ψϕ B b B c c J/ ψ ϕ B b u,c,t W ± b W± B u,c,t ϕ predicted to be very mall in Standard Model New Phyic enitivity golden channel : time-dependent CP aymmetry in B J/ ψ ϕ complication 1: lifetime difference Δ Γ between the two CP-Eigentate of the B /B ytem not well known ha to be determined imultaneouly complication 2: J/ ψ ϕ not produced in a CP Eigentate need timedependent angular analyi to eparate CP even/odd component bet contraint o far: CDF (5.2 fb-1) [CDF Note 126] D (6.1 fb-1) [D 698-CONF] LHCb Phyic, Performance, Propect (23/28)

24 B B Mixing Phae ϕ = 2β LHCb: tatitic from 21 data et too mall for competitive meaurement ued the data uccefully to validate all apect of analyi procedure obtained firt contraint in ϕ / Δ Γ plane ϕ SM [ 2.7,.5] 68 CL [LHCb-CONF-211-6] preliminary good new: ytematic very mall expect world bet meaurement of ϕ from 211 data LHCb Phyic, Performance, Propect (24/28)

25 Rare Decay: B μ μ + very rare in Standard Model: BR(B μ + μ ) = (3.2±.2) 1 9 [Bura, arxiv: ] but can be ignificantly enhanced by New Phyic not yet oberved, bet upper limit o far from Tevatron CDF (3.7 fb-1): BR < CL [CDF note 9892] DØ (6.1 fb-1): BR < CL [PLB 693 (21) 539] meauring branching fraction above Standard Model prediction would be clear ign for new phyic improving on the upper limit contrain parameter pace for New Phyic model e.g. Minimal Superymmetric Standard Model BR(B μ μ ) tan β ma4 LHCb Phyic, Performance, Propect (25/28)

26 Rare Decay: B μ μ + advantage LHCb: large B production rate, excellent ma reolution claify event according to μ +μ - invariant ma and GL: multi-variate claifier exploiting characteritic of the two-body event topology ditance of cloet approach of the two μ', their iolation and impact parameter wrt primary vertex impact parameter, pt and lifetime of B candidate calibrate GL on B h+ h ' event etimate invariant ma reolution from B h h ' + + and from J/ ψ, ψ (2) μ μ, Υ (1), (2), (3) μ μ + expected excluion 9% CL oberved number of event in bin of invariant ma and GL compatible with expected background BR(B μ + μ ) < 4.3 x 1 9 % CL [Phy.Lett.B 699 (211) 33] now LHCb Phyic, Performance, Propect (26/28)

27 Long-Term Outlook (mentioned today) LHCb Phyic, Performance, Propect (27/28)

28 Concluion LHCb ha a unique potential for the INDIRECT DISCOVERY OF NEW PHYSICS both the LHC and the experiment are performing very well in ome analye already competitive reult from the 21 data et already 1x more data on dik, taken under much more table condition expect to collect 1 fb-1 by the end of thi year expect many world-bet meaurement from 211 data tay tuned... [p. could only ketch a tiny fraction of the many analye under way] [in particular, did not ay anything about Charm] LHCb Phyic, Performance, Propect (28/28)