1 / 30

LHCb Physics, Status, and Perspectives

This paper discusses CP violation in the Standard Model, focusing on unitarity testing of the CKM matrix and potential impacts of new physics on mixing phases. It explores precision measurements, unitarity triangles determination, and challenges in particle decay observations. The study emphasizes the need for high-statistics data and sensitive tests using Bd and Bs mesons to probe CP-violation mechanisms further. It offers insights into potential scenarios and the importance of LHCb measurements in understanding weak decay phases and particle interactions.

foremans
Download Presentation

LHCb Physics, Status, and Perspectives

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. LHCbPhysics, Status, and Perspectives Bernhard Spaan Technische Universität Dresden on behalf of the LHCb Collaboration • Motivation • CP Violation, Tests of the Standard Model • LHCb • Design, Status • Physics Reach • Conclusions 4th Four Seas Conference, Istanbul 2004 Supported by bmbf:

  2. LHCb: a dedicated B-Physics Experiment at the LHC 565 scientists 47 universities and laboratories 15 countries Geneva CERN LHCb ATLAS CMS ALICE LHC Tunnel

  3. CP µ– µ W– b Vcb c CP-Violation in the Standard Model • Standard model: Origin of CP-Violation: Higgs-Sector! • Higgs: • responsible for mass generation of all particles • Quark-Mass-Mixing matrix • Cabibbo Kobayashi Maskawa (CKM) Matrix weak eigenstates C: Charge Conjugation P: Parity CKM Matrix: • complex • unitary • 4 parameters: • 3 Euler angles • 1 Phase mass eigenstates

  4. CP-Violation in the Standard Model SM CP violation > 10 orders of magnitude too small to explain matter antimatter asymmetry in the universe • test whether observable CP-Violation can be explained by the Standard Model  origin of observable CP-violation? test unitarity of CKM matrix BTW: Lepton sector may offer other mechanisms to generate sizeable matter antimatter asymmetry in the universe.

  5. Unitarity Test of the CKM-Matrix: 6 unitarity conditions Unitarity Test:  overconstrain Unitarity Triangles  determine angles and magnitude of sides Representation as „Unitarity Triangles“: 6 Triangles are possible, all with the same area. However, 4 of them are are almost degenerated and do not allow a sensitive unitarity test. Sensitive tests: Bd- and Bs-mesons   

  6. CKM Parametrizations Vhas 4 observable parameters and an infinite number of choices for these 4 L. Wolfenstein 1983: ,A,, relevant for Bs Small „phase“ forVts Tiny imaginary correction forVcd Expect sizeable „phases“ for:Vub, Vtd, and Vts,

  7. Unitarity Triangles : Bdmixing phase : Bsmixing phase : weak decay phase Im  Wolfenstein:Vub= ei   Almost identical triangles (differences at the percent level) 0 1 Re Im   + Precision Test requires measurements with Bu-, Bd-, andBs-mesons  0 Re

  8. Mixing new particle loop New Physics may influence mixing Phase!  shifted,  ?  Unitarity Triangle may not close! CP in Interference between Mixing and DecayB0J/KS vs Bs J/ Oscillations dominated by top quark Vtb Vtd Wolfenstein: only „real“ CKM elements in decay  no weak phase need to considerV

  9. Unitarity Triangle - 2004 Hardly any constraint on  Possible scenario in 2007 before LHCb • Need Precision Measurement on  • LHCb decrease errors on  and  • LHCb sin2 Possible impact of a LHCb measurement on  sin2  (LHCb)

  10. new particle loop new particle loop new particle loop Penguins & Co B0J/KS Tree B0KS • Pure Penguin (bsss)– same weak phase as in bccs should yield sin2 • Difference to sin2 from BJ/KS Hints for New Physics??  large potential for detection of New Physics in modes with penguin contribution need high statisticsLHCb sin2: 2.7s sin2: 2.4s

  11. Penguins & Co Small Branching Fractions More interesting penguin mediated modes: e.g. Tree Penguin • Need huge statistics! • LHCb + look for other rare Decays e.g. B+

  12. p p „sea quarks“ B production in pp Collisions at s = 14 TeV (LHC) Interactions of 2 partons (quarks, gluons) with fractional momenta xi Parton 2 x2 Parton 1 x1 p p Examples: all b-hadron species are produced: Challenge compare with ~40% ~40% ~10% ~10% @

  13. Boost B production • B hadrons are mostly produced in the forward (beam) direction • Choose a forward spectrometer10–300 mrad • Both b and b in the acceptance: important for tagging the production state of the B hadron • Efficient Trigger needed b–b correlation (PYTHIA)

  14. LHC environment • Bunch crossing frequency: 40 MHz • sinelastic = 80 mb at high L >> 1 pp collision/crossing  run at <L> ~ 2 × 1032 cm-2s-1 dominated by single interactions • Reconstruction easier • e.g. b-quark vertex identification • Lower radiation level • Beams are defocused locally to maintain optimum luminosity even when ATLAS and CMS run at <L> ~ 1034 cm-2s-1 • LHCb-detector must be able to operate in a high rate and high multiplicity environment Inelastic pp collisions/crossing

  15. Time Resolved Measurements sin2, sin2, (), Oscillations Measurements ms, …… • opposite side lepton and kaon tag • same side kaon tag (for Bs) • opposite B vertex charge tagging Flavour-determination of other b-Quark („tag“)  Flavour of Brec at t=0 p- 0 K s m- p+ K- D0 p+ B0 D*+ p+ • Exclusive B-reconstruction • (e.g. CP Eigenstates)  Measure momentum p from decay products (1-100 GeV/c) • Identify decay products (Leptons, /K separation) B0  e+ J/ nm e- • Determination of t = /c • typically 1 cm in LHCb (very high vertex resolution for Bs measurements required)

  16. LHCb Requirements • Efficient trigger for many B decay topologies (large non B-Backgrounds!) • Leptonic final state →Muonsystem, ECAL + Preshower • Hadronic final state →HCAL • High pt-particles with large impact parameter →VELO,TT • Efficient particle identification • π/K separation (1<p<100GeV) →RICH • Good decay time resolution→VELO • Good mass resolution →Tracker and Magnet • Must work in high rate and high multiplicity environment Vertex Locator Trigger Tracker

  17. LHCb Requirements DISTINGUISH/K Search for rare decays e.g. Bd,s+ - O(10-9) in SM Precision measurements on CPV and with e.g. BKs, J/, K*, K(*)+ HIGH STATISTICS

  18. LHCb detector ~ 250 mrad p p 10 mrad  Forward spectrometer (running in pp collider mode) Inner acceptance 10 mrad from conical beryllium beam pipe

  19. LHCb detector Silicon strip sensors mounted in Roman Pots (inside vacuum) made in two halves in roman pots very close to beamline (starts at 8 mm)  can be retracted e.g. during injection  Vertex locator (VELO) around the interaction region Silicon strip detector with ~ 30 m impact-parameter resolution

  20. T3 T2 T1 OT IT TT Assembly completed, rolled into position LHCb detector TT: 144k channels, Silicon Strip IT: 129k channels, Silicon Strip OT: 54k channels, Straw Tubes  Tracking system and dipole magnet to measure angles and momenta p/p ~ 0.4 %, mass resolution ~ 14 MeV (for Bs DsK)Magnetic field will be reversed to reduce experimental systematics

  21. LHCb detector  Two Cherenkov detectors (RICH) for charged hadron identification  > 3s p–Kseparation for 3 < p < 80 GeV

  22. RICH Entrance/exit window RICH2 Photon Detector: Hybrid PhotoDiodes HPD – 1024 pixels – LHCb development  ordered Mechanics/mirrors/detectors: under construction/ordered

  23. LHCb detector e h  Calorimeter system (Preshower PS/SPD, ECAL and HCAL) provides Identification of electrons, hadrons and neutrals Important for the first level of the trigger

  24. Calorimeters ECAL PS/SPD HCAL Preshower (Scintillator Pad) ~25% of modules completed ECAL (shashlik) 100% of modules completed HCAL (Scintillator Tile) ~60% of modules completed

  25. 1368 MWPC‘s production started LHCb detector m  Muon system to identify muons, also used in first level of trigger Efficiency ~ 95% for pion misidentification rate < 1%

  26. Simulated Event

  27. Some Efficiencies and yields 1012 bb pairs per year produced (nominal year) Yields include CP-conjugated decays Branching ratios are from PDG or SM predictions

  28. BsBs-Oscillations proper time resolution ~ 40 fs Best channel for LHCb: ms = 25ps-1 • can make a 5 measurement in one year of running for ms up to 68 ps-1 (far beyond Standard Model expectation < 26ps-1) • once oscillations are established  determine ms with (ms)~0.01 ps-1

  29. Performance figures (1 year, 2 fb-1)

  30. Conclusions • LHCb: a dedicated B-Physics Experiment at LHC • all B-Hadron species accessible • huge statistics compared to B-Factories • ready for data taking in 2007 • Construction of the experiment is progressing well • Installation of first components started • Already after the first year of data taking, LHCb will have competitive measurementson, , , ms…… • Rare decays will become increasingly important • LHCb: huge statistics and excellent detector performance provide excellent opportunities to search (find?) New Physics

More Related