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First Results from LHCb Yu. Guz (IHEP Protvino), on behalf of the LHCb collaboration 24 September 01 October 2011, Sochi, Russia The XXth International Workshop High Energy physics and Quantum Field Theory LHCb detector Selected physics results LHCb upgrade issues Conclusions

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2 LHC is a pp collider with E CM = 14 (or 7) TeV and luminosity up to 10 34 cm -2 s -1

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The LHCb experiment at LHC 3 b b b b LHC is good as a B factory: the bb cross section (pp bbX) is large, ~300 b The bb production is sharply peaked forward- backward. LHCb choice: a single arm detector 1.94 GeV/c misID 2.4%, p 0.18% BR( )=5.80.810 -6

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Trigger Hardware Level-0 trigger followed by two-stage software High Level Trigger, HLT1 and HLT2 L0 requires presence of a high p T object (h, , , , e ) in CALO and Muon system HLT1 performs partial reconstruction, confirms L0 objects: associates them with reconstructed tracks, especially with those displaced from the PV HLT2: full reconstruction; uses reconstructed objects for exclusive selections with clear signature Depending on luminosity, the L0 and HLT thresholds can be tuned such that not to exceed maximal throughput of the systems. First data of 2010 with low LHC luminosity: loose trigger conditions, data suitable for production studies. Since summer 2010 trigger optimized for B-physics 9 Yu. Guz QFTHEP-2011 First Results from LHCb Average event size ~35 kB 10 MHz 850 KHz 3 KHz

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LHCb running in 2011 10 Yu. Guz QFTHEP-2011 First Results from LHCb The luminosity is limited, in particular, by requirement from reconstruction of not too many visible pp interactions in one event (). LHC does luminosity leveling for LHCb by varying the bunch overlap Currently, at LHC energy of 2x3.5 TeV, LHCb is running at L 3.510 32 cm -2 s -1. With ~1400 bunches in LHC, this corresponds to 1.3 (the original design parameters for 2x7 TeV running with ~2800 bunches were L 210 32 cm -2 s -1 and 0.4 ).

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LHCb luminosity 11 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb is running smoothly since the LHC startup, no major hardware problems, the detector is > 99% operational. 2010 2011 1 fb -1 expected by the end of 2011, same (or more) in 2012

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Selected physics results

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Mass measurements 13 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb-CONF-2011-027 LHCb, MeV/c 2 5279.17 0.29 5279.50 0.30 5366.30 0.60 5620.2 1.6 6277 6 PDG Performed with 2010 data, 37 pb -1. More precise than PDG values!

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Lifetime measurements 14 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb-CONF-2011-001 Performed with 2010 data, 37 pb -1. 1.638 0.011 1.525 0.009 1.477 0.046 1.391 0.038 PDGLHCb, ps Bs J/ , t > 0.3 ps

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bb production 15 Yu. Guz QFTHEP-2011 First Results from LHCb The pp bb cross section was measured in two ways: deduced from J/-from-b production cross-section using the LEP average b J/ branching fraction and extrapolating into 4 (see talk of K. Belous): (pp bbX)=288 448 b measured using b D 0 X - (+cc) inclusive yields gives a compatible result: (pp bbX)=2842049 b In this analysis the b decay candidates were selected as D 0 ( K - + ) and - having common vertex; the right sign combinations has significant nonzero impact parameter (IP) of D 0 ( K - + ), which is a signature of a true b decay. PL B694 (2010) 209 EPJ C71 (2011) 1645 wrong sign (D 0 +) combinationright sign (D 0 -) combination all D 0 K-+ candidates

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B + production 16 Yu. Guz QFTHEP-2011 First Results from LHCb The B+ production total and differential cross-section were measured in the LHCb acceptance in B + J/K + : (B+, 2

s from B s J/ 22 Yu. Guz QFTHEP-2011 First Results from LHCb 827694 The lifetime cut t>0.3 ps removes most of the background, resulting in total of 827694 signal events. Only OS flavor tagging used for the J/ analysis, calibrated on J/K* : D=0.2770.0110.025, tag = (2.080.41)% LHCb-CONF-2011-049 Proper time resolution was calibrated on prompt J/: t ~50 fs. per-event mistag probabilities

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s from B s J/ 23 Yu. Guz QFTHEP-2011 First Results from LHCb Goodness of fit was checked using the point-to-point dissimilarity test ( arXiv:1006.3019 ). LHCb-CONF-2011-049 [3.01, 3.36] @ 68% CL The 4% KK S-wave contribution. The systematic errors mainly come from uncertainties in the description of angular and decay time acceptance and background angular distribution.

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s from B s J/ 24 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb-CONF-2011-049 SM To date, worlds most precise result: s = 0.13 0.18(stat) 0.07(syst) s = 0.656 0.009(stat) 0.008(syst) s = 0.123 0.029(stat) 0.008(syst) - first 4 evidence of s > 0 ! Expectations for 2 fb -1 of 2011+2012 s statistical uncertainty of ~0.07 from simple scaling further improvement of statistical uncertainty from including same side tagging reduction of systematic errors from better understanding of acceptance and background

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s from B s J/ 25 Yu. Guz QFTHEP-2011 First Results from LHCb From http://lhcb-public.web.cern.ch/lhcb-public

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s from B s J/ f 0 (980) 26 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb-CONF-2011-051 CP-odd final state, cannot determine s and s simultaneously. CL contours obtained using s from J/. Using both s and s from B s J/: s =-0.440.44(stat)0.02(syst) When combining B s J/ and B s J/f 0 (980): s =-0.03 0.16(stat) 0.07(syst) LHCb-CONF-2011-056 The decay B s J/f 0 (980) first observed by LHCb, CERN-PH-EP-2011-011

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B s 27 Yu. Guz QFTHEP-2011 First Results from LHCb +NP BR much lower than Bs J/ . As a first stage - measurement of time-integrated triple product asymmetry In SM both A U/V =0. Non-zero measurement means weak phase difference between CP even and odd eigenstates, clear sign of NP [M. Gronau and J. L. Rosner, arXiv:1107.1232], U=sin(2), V=sin(), sign from cos( 1 )*cos( 2 ) Proceeds via b s FCNC penguin, possible New Physics contribution can be revealed e.g. through comparison of CPV phase with the one obtained from Bs J/

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B s 28 Yu. Guz QFTHEP-2011 First Results from LHCb Studied with 340 pb -1 of data. Very clean mass peak. No flavour tagging needed for triple product asymmetry Consistent with zero Next step : time-dependent CP asymmetry measurements (needs more statistics) LHCb-CONF-2011-052 AU=-0.0640.0570.014AV=-0.0700.0570.014

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direct CP asymmetry in B d,s K 29 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb-CONF-2011-042 A cp (B d K) = -0.0880.011(stat) 0.008(syst) World Average = -0.098 A cp (B s K) = 0.270.08(stat) 0.02(syst) - first evidence +0.012 -0.011 Non-physical asymmetries A were evaluated: A (B d K) = -0.007 0.006 A (B s K) = -0.010 0.002

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B s,d Very rare in SM (FCNC & helicity suppressed): BR(B s ) SM =(3.20.2)10 -9 ; BR(B d ) SM =(1.10.1)10 -10. 30 Yu. Guz QFTHEP-2011 First Results from LHCb Previous measurements: D0: BR(B s ) < 5.110 -8 (95%) (6.1 fb -1 ) PL B693, 539 (2010) CDF: BR(B s ) = (1.8 )10 -8 (hint !) (7 fb -1 ) arXiv:1107.2304 LHCb: BR(B s ) < 5.610 -8 (95%) (6.1 fb -1 ) PL B699, 330 (2011) Recent CMS measurement: BR(B s ) < 1.910 -8 (95%) (1.1 fb -1 ) arXiv:1107.5834 +1.1 - 0.9 A.J.Buras, arXiv:1012.1447 see talk by Yu. Shcheglov May be significantly enhanced in models with S or P coupling; e.g. in MSSM BR(B s.d ) ~ tan 6 / M A 4, a good probe for New Physics! World best limits obtained by LHCb with 300 pb -1 of 2011 (+37 pb -1 of 2010) BR(B s ) < 1.5 (1.2) 10 -8 at 95% (90%) CL BR(B d ) < 5.2 (4.2) 10 -9 at 95% (90%) CL

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B s 31 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb-CONF-2011-047 CMS PAS BPH-11-019 Combined with recent CMS result: BR(B s ) < 1.08 (0.90) 10 -8 at 95% (90%) CL Prospects for LHCb taken from arXiv:1108.3018 see talk by Yu. Shcheglov

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Other LHCb results 32 Yu. Guz QFTHEP-2011 First Results from LHCb Physics results not covered here: studies of radiative decays B s and B d K*. FB asymmetries in B K*; CPV in charm, measurement of A and A CP : results of 2010 available, 2011 expected soon LFV search in B K(); CP asymmetry in B + DK + ; B c production and decays; b baryons; and more LHCb-CONF-2011-042 LHCb-CONF-2011-046 LHCb-CONF-2011-023 LHCb-PAPER-2011-009 LHCb-CONF-2011-023 LHCb-CONF-2011-038

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LHCb Upgrade

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LHCb long term plans 34 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb Upgrade LoI: CERN-LHCC-2011-001 By 2017, LHCb is expected to take 5-10 fb -1 of data. There is strong physics motivation to continue the present programme. Next step is to collect other ~50 fb -1 probe / measure NP effects at % level. For this, LHCb should be able to run at higher luminosities: (1-2)1033 @s = 14 TeV. Upgrade is necessary

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LHCb upgrade plan 35 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb Upgrade LoI: CERN-LHCC-2011-001 LHCb at higher luminosity typical L0 efficiency for purely hadronic final states ~ 50% and will drop with luminosity. The acquisition rate for purely hadronic channels (like Bs ) does not increase with increasing luminosity! apart from the trigger, the LHCb performance will not deteriorate significantly up to 10 33 cm -2 s -1 The only way out is to replace the present hardware L0 trigger by a flexible software one which is able to digest the full input bandwidth, up to 40 MHz. This implies replacement of almost all the frontend electronics.

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LHCb upgrade plan 36 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb Upgrade LoI: CERN-LHCC-2011-001 Presently: hardware L0 software HLT1 with max 1 MHz input HLT2 with up to 2 (3) kHz output run now at 3.5 10 32 cm -2 s -1 @ s=7 TeV Upgrade: fl;exible software LLT up to 40 MHz input up to 20 kHz HLT output run at 5 times higher luminosity big gain for hadronic modes

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Detector issues 37 Yu. Guz QFTHEP-2011 First Results from LHCb VELO: replace the whole detector (rad damage). New readout chips. Choice between strip and pixel options. other tracking detectors: leave present OT straw tubes at the periphery. Middle part: the options are silicon strips or scintillating fibers. RICHes: replace all the photodetectors, as present HPDs include readout electronics. MAPMTs is baseline. Remove aerogel in RICH1 (material budget). additional PID detector: Time of Internally Reflected Cherenkov Light (TORCH). Quartz plate radiator, 10-15 ps resolution. Installed between RICH2 and calorimeters. CALO: reduce PMT gain. Possible replace few modules in hottest areas. Removing part of the preshower is discussed. MUON: present frontend electronics can be kept and read out at 40 MHz. remove the M1 station before calorimeters.

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Conclusions 38 LHCb is running successfully at its design luminosity (and beyond!), demonstrating very good detector performance, and collected by now ~800 pb -1 of physics data already now, LHCb obtained physics results competitive with B-factories and Tevatron experiments: most precise direct CP violation measurements in B d,s K most precise measurement of m s, most precise measurement of s and s in B s J/, J/f 0 (980), best upper limits on rare decay B s by now, no significant deviation from SM observed, in particular the hints observed by Tevatron in B s and s not confirmed 1 fb -1 expected by the end 2011, more in 2012. Many important physics results expected! high luminosity upgrade is foreseen. Yu. Guz QFTHEP-2011 First Results from LHCb

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Thank you!

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Backup

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Luminosity measurement in 2010 41 Yu. Guz QFTHEP-2011 First Results from LHCb N number of bunches f collision frequency n 1i, n 2i -- # of protons in bunches Xi, Yi transverse bunch sizes LHCb preliminary 2009, E CM =0.9 TeV In 2010, luminosity will be estimated from beam properties Determined with ~15% accuracy in 2009 (dominated by the bunch current measurement uncertainty). In 2010 5-10% precision is expected.

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Lepton flavor violation 42 Yu. Guz QFTHEP-2011 First Results from LHCb Looking for DL=2 processes B + K - + + and B + + + (allowed in NP models with a Majorana neutrino) No signal observed in 36 pb -1 Improved present best limits by a factor of 40 (30). Publication in preparation. LHCB-PAPER-2011-009

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B s 43 Yu. Guz QFTHEP-2011 First Results from LHCb Experimental probe: A (or effective lifetime) [F. Muheim, Y. Xie, R. Zwicky, PLB 664:174, 2008] A sensitive to fraction of right-handed photons (even for small s ) A ~ 0 in SM, can be enhanced by NP with large RH currents. Dominating SM quark level diagram has left handed photons An example MSSM diagram with right-handed photons

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B s 44 Yu. Guz QFTHEP-2011 First Results from LHCb LHCb-CONF-2011-055 First step: measure BR. Next step: measure A (or effective lifetime) B d K* B s