The LHCb Experiment On behalf of the LHCb Collaboration presented at Hadron99, Beijing, 24-28 August 1999 On behalf of the LHCb Collaboration Tatsuya Nakada* CERN, Switzerland *on leave from PSI

Introduction CP violation is observed only in the neutral kaon system: e: CP violation in K-K oscillations e: CP violation in the decay-oscillation interplay e: CP violation in the decay amplitudes They are within the framework of the Standard Model: KM phase. However, 1) no “precision” test has been made… (difficult with the kaon system due to theoretical uncertainties) 2) no real understanding, on the origin of the mass matrix… (Why strong CP is small but weak CP not?) 3) Cosmology (baryon genesis) suggests that an additional source of CP violation other than the Standard Model is needed. A lot of room for new physics  B-meson systems _

The B-meson system is an ideal place to search for new physics through CP violation. 1) For some decay modes, the Standard Model predictions can be made accurately. - precision tests - 2) CP violation can be seen in many decay channels. - consistency tests - The system allows to extract the parameters for both the Standard Model and new physics, if it exists.  a simple demonstration to follow

CKM Unitarity Triangles VtdVtb + VcdVcb + VudVub = 0 VtdVud + VtsVus + VtbVub = 0   Vub Vtd Vtd Vub      Vcb Vts arg Vcb = 0, arg Vub = , arg Vtd = , arg Vts = 

Extensions to the Standard Model Supersymmetry, left-right symmetric model, leptoquark, … etc. all introduces new flavour changing neutral currents Db = 1 process: Decays through penguin Db = 2 process: Oscillations through box through tree b d, s new particles b d, s l or d,s b new particles b d, s l or new particles d,s b 1

CKM and new physics in the oscillation amplitudes |Vtd*Vtb|2 _ _ HB-B  [{(1 - r)2 + h2}+ rdb] e2i(b + fdb) Bd-Bd oscillations Dmd CP in BdJ/y KS _ |Vts*Vtb|2 _ Bs-Bs oscillations HB-B  [ l-2 + rsb ] e-2i(dg + fsb) Dms CP in Bs J/y f CP in Bd J/y KS due to the interference b c J/y c Bd Bd J/yKS W Bd s _ KS d d _ HB-B  e-2i(b + fdb) ABJ/yKs  Vcb* Vcs  e0i

A consistency test by comparing the two gKM then combine them to CP violation in Bd  J/y KS v.s. Bd  J/y KS measures 2bJ/yK = 2(bKM + fdb) _ CP violation in Bd  D*+ np v.s. Bd  D*- np Bd  D*- np v.s. Bd  D*+ np measures 2(bKM + fdb ) +gKM _ _ A consistency test by comparing the two gKM then combine them to improve the precision CP violation in Bs  J/y f v.s. Bs  J/y f measures 2bJ/yf = 2(dgKM + fsb) Bs  Ds+ K- v.s. Bs  Ds- K+ Bs  Ds- K+ v.s. Bs  Ds+ K- measures 2(dgKM + fsb) +gKM _ _ _

semileptonic decays are least effected by new physics |Vtd| = (1 - rKM)2 + hKM 2 Measured Gbu  rKM2 + hKM2 bKM: CKM angle Vtd  e-ibKM hKM r rKM 1 Measured gKM from CP violation in BdD*np, BsDsK

determination of CKM parameters 1) gKM is determined 2) |Vub| and gKM  bKM or (rKM, hKM) determination of CKM parameters 3) hKM  dgKM 4) (rKM, hKM)  |Vtd| and |Vts| 5) bJ/yK and bKM  fdb determination of new physics parameters 6) bJ/yf and dgKM  fsb 7) Dms, Dmd and (rKM, hKM)  rdb and rsb Both CKM and New Physics parameter sets are fully and cleanly determined. (and many other examples)

Potential problems for BaBar, BELLE, CDF, D0, HERA-B J/yKS very high statistics for a precision D*np small asymmetries require high statistics, low background DsK need Bs (problem for BaBar, BELLE) particle ID at large p (problem for CDF, D0) small branching fractions <10-5 require high statistics J/yf need Bs (problem for BaBar, BELLE) large statistics needed to obtain CP=+1/CP=-1

The LHCb experiment Operating at the most intensive source of Bu, Bd, Bs and Bc, i.e. LHC with -particle identification -trigger efficient for both leptonic and hadronic final states. (ATLAS and CMS: no real particle ID and only with lepton triggers)

The LHCb Experiment (~450 people, ~50 institutes) Brazil USA Finland Ukraine France UK Germany Switzerland Italy Poland PRC Netherlands Romania Russia Spain

The LHCb Collaboration (August 99) Finland: Espoo-Vantaa Inst. Tech. France: Clermont-Ferrand, CPPM Marseille, LAL Orsay Germany: Humboldt Univ. Berlin, Univ. Freiburg, Tech. Univ. Dresden, Phys. Inst. Univ. Heidelberg, IHEP Univ. Heidelberg, MPI Heidelberg, Italy: Bologna, Cagliari , Ferrara, Genoa, Milan, Univ. Rome I (La Sapienza), Univ. Rome II(Tor Vergata) Netherlands: Univ. Amsterdam, Free Univ. Amsterdam, Univ. Utrecht, FOM Poland: Cracow Inst. Nucl. Phys., Warsaw Univ. Spain: Univ. Barcelona, Univ. Santiago de Compostela Switzerland: Univ. Lausanne UK: Univ. Cambridge, Univ. Edinburgh, Univ. Glasgow, IC London, Univ. Liverpool, Univ. Oxford CERN Brazil: UFRJ China: IHEP(Beijing), Univ. Sci. and Tech.(Hefei), Nanjing Univ., Shandong Uni. Russia: INR, ITEP, Lebedev Inst., IHEP, PNPI(Gatchina) Romania: Inst. of Atomic Phys. Bucharest Ukraine: Inst. Phys. Tech. (Kharkov), Inst. Nucl. Research (Kiev) U.S.A.: Univ. Virginia, Northwestern Univ., Rice Univ.

IP 8

The LHCb Detector Vertex detector: Si r-f strip detector, single-sided, 150mm thick, analogue readout Tracking system: Outer; drift chamber with straw technology Inner; Micro Strip Gas Chamber with Gaseous Electron Multiplier, Micro Cathode Strip Chamber or Si RICH system: RICH-1; Aerogel (n = 1.03) C4F10 (n = 1.0014) RICH-2; CF4 (n = 1.0005) Photon detector; Hybrid Photon Diodes (backup solution PMT) Calorimeter system: Preshower; Single layer Pb/Si (14/10 mm) Electromagnetic; Shashilik type 25X0, ~10% resolution Hadron; ATLAS design tile calorimeter 5.6l, <80% resolution Muon system: Multi-gap Resistive Plate Chamber or Thin Gap Chamber and Cathode Pad Chamber

Physics capability of the LHCb detector is due to: -Trigger efficient for both lepton and hadron high pT hadron trigger 2 to 3 times increase in pp, Kp, D*p, DK*,Dsp, DsK … Dsp: 34k (flexible and robust) -Particle identification e/m/p/K/p pp, Kp, D*p, DK*, Dsp, DsK -Good mass resolution e.g. 11 MeV for Bs  Dsp, 17 MeV for Bd  p+p- (particle ID + mass resolution  redundant background rejection) -Good decay time resolution e.g. 43 fs for Bs  Dsp, 32 fs for Bs  J/yf

Trigger: Flexible: Multilevel with different ingredients Robust: Evenly spread selectivities over all the levels Efficient: High pT leptons and hadrons (Level 0) Detached decay vertices (Level 1)

LHCb Trigger Efficiency for reconstructed and correctly tagged events L0(%) L1(%) L2(%) Total(%)  e h all BdJ/(ee)KS + tag 17 63 17 72 42 81 24 BdJ/()KS + tag 87 6 16 88 50 81 36 BsDsK + tag 15 9 45 54 56 92 28 BdDK        Bd + tag 14 8 70 76 48 83 30 - trigger efficiencies are ~ 30% - hadron trigger is important for hadronic final states - lepton trigger is important for final states with leptons

Major background: Bs  Ds(No CP violation) Bs  DsK Major background: Bs  Ds(No CP violation) Importance of particle identification and mass resolution

Bs-Bs oscillations with BsDs _ Bs-Bs oscillations with BsDs 120 k reconstructed and tagged events measurements of mswith a significance >5: up to psxs

The LHCb detector, a forward spectrometer with particle ID, will have a wide programme in heavy flavour physics. CP violation: Bd  p+p- rp K±pm fKS K*0g K*0l+l- … Bs  K+ K- K±pm ff fKS fg fl+l- … rare and forbidden decays: Bs, d  m+m-, m±em ... Bc meson decays b-baryon spectroscopy etc. tree + penguin penguin only

Conclusions LHCb has been approved in September 1998,  preparing for Technical Design Reports. Construction will start the beginning of 2001. LHCb is one of the four baseline LHC experiments,  taking data from the day one. Efficient and robust trigger  the optimal luminosity 21032 exploiting the physics potential from the day one. Locally tuneable luminosity  long physics programme. Effective trigger, particle ID, decay time and mass resolution  essential to reveal New Physics from CP violation. (not possible by the general purpose LHC experiments)

LHCb CP Sensitivities in 1 year (work still in progress) Parameter Channels No of events (1 year) LHCb feature 2(+) Bd + c.c. 6900 |P/T| = 0 2-5 PID, hadron trigger Bdr + c.c. ~1000 in progress PID, hadron trigger 2+ Bd  D* 446000 9 PID, hadron trigger  BdJ/Ks 45000 0.6 -2 Bs DsK 24000 6-13 PID, hadron trigger, t  Bd  DK* 400 10 PID, hadron trigger  Bs  J/yf 44000 0.6 t Bs oscillations xs Bs  Ds 120000 upto 75 hadron trigger, t Rare Decays Br Bs   <210-9 t No. Bd  K*  26000 photon trigger