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High precision CP violation physics at LHCb

Meeting of the EPFL Research Commission, EPFL, November 30, 2004. High precision CP violation physics at LHCb. presented by Olivier Schneider. On-going, long-term project supported in Lausanne since several years by SNSF and FORCE grants (FORCE = Fonds pour la Recherche au CERN):

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High precision CP violation physics at LHCb

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  1. Meeting of the EPFL Research Commission, EPFL, November 30, 2004 High precision CP violation physics at LHCb presented by Olivier Schneider • On-going, long-term project supported in Lausanne since several years by SNSF and FORCE grants(FORCE = Fonds pour la Recherche au CERN): • Co-applicants: • Prof. A. Bay, LPHE • Prof. T. Nakada, LPHE • Prof. O. Schneider, LPHE • Dr. Minh-Tam Tran, LPHE • Main project of the LPHE(Laboratoire de Physique des Hautes Energies) • LHCb experiment in preparation at CERN by a large international collaboration Contents: – CP violation, B physics … – LHCb physics goals – LHCb experiment – LPHE’s involvement and responsibilities

  2. CPLEAR experiment at CERN, Phys. Lett. B 363, 243 (1995) p+ p- K0 K0 CP is violated ! p- p+ CP mirror Number of observed decays in , N(K ) K0  p+p- K0  p+p- Measured proper time t / (KS) CP symmetry: textbook example Parity P: left  right Charge conjugation C: q  –q CP: matter  antimatter If CP is conserved, the probability for a K0 to decay to  after a certain proper time t should be the same as that of an anti-K0. Meeting of EPFL Research Commission

  3. Quarks can only appear as “colourless” combinations (=hadrons): u u s b d d d u d • Forces are described as exchange of bosons (e.g. photon for the electromagnetic, W± and Z for the weak interaction) 1015 m Feynman diagram: time Standard Model (SM) of particle physics • Matter is made of fermions (spin 1/2) • Each fermion has an anti-matter counterpart Meeting of EPFL Research Commission

  4. weak states mass states CKM matrix Quarks Anti-quarks CP violation in the Standard Model • Higgs field (yet to be discovered !) generates mass of particles • Quark mass eigenstates are different from weak eigenstates quark mixing matrix (Cabibbo, Kobayashi, Maskawa) Vij proportional to transition amplitude from quark j to quark i Different mixing matrix for quarks and anti-quarks  CP violation Meeting of EPFL Research Commission

  5. Im   Re  0 1 CP violation in the Standard Model • CKM matrix: • complex and unitary  4 parameters (e.g. 3 angles and 1 phase) • 6 unitarity triangles • most sensitive experimentaltests on the two unsquashedtriangles, with transitionsinvolving b quarks responsible for CP violation “Unitarity triangle” (area CP violation) Meeting of EPFL Research Commission

  6. New Physics ? ? ? ? ? ? – Bs decay: “Penguin” diagram B0–B0 oscillations: “Box” diagram 0 Physics beyond the Standard Model ? • Cosmological argument: • Our Universe displays obvious matter-antimatter asymmetry • Evolution from symmetric situation at Big Bang requires CP (Sakharov) • CP violation in SM far too small to explain  other sources of CP must exist • New particles ? • Motivated from theories of grand unification, supersymmetry, dark matter, … • Almost every SM extension implies new sources of CP • May be observed directly (if produced in high-energy collisions), or indirectly in “loop” processes (even at lower energies) • Examples of loop processes: Standard Model Meeting of EPFL Research Commission

  7. CKM unitarity triangle as measured today Physics goals of LHCb High-precision measurements of CP violation with B decays and study of rare B decays search for New Physics Possible scenario in 2007 before LHCb Possible impact of an LHCb measurement Meeting of EPFL Research Commission

  8. LHC = Large Hadron Collider Start operation in 2007 Proton bunch spacing: 7.5 m = 25 nsProton-proton collisions at 14 TeV World’s largest beam energy and most intense source of b hadrons Genève CERN LHCb (B physics, CP violation) ATLAS (Higgs, ...) Rates at LHCb: ~16 MHz of pp interactions 0.1 MHz of b hadrons Huge statistics CMS (Higgs, ...) ALICE (heavy ion collisons, quark-gluon plasma) LHC tunnel (27 km = 0.09 ms) Meeting of EPFL Research Commission

  9. VELO: Vertex Locator (around interaction point) TT, T1-3: Tracking stations RICH1-2: Ring Imaging Cherenkov detectors ECAL, HCAL: Calorimeters M1-5: Muon stations VELO proton beam proton beam B B = 1.5 ps 1 mm LHCb detector collision point Meeting of EPFL Research Commission

  10. Technical challenges • Imposed by LHC environment and physics requirements • Examples:Typical/nominal values • Fast detectors and front-end electronics 25 ns cycle • Radiation-hard detectors and front-end electronics ~1014 neq/cm2/y at r = 8 mm • Pattern recognition in dense environment ~72 rec. tracks per bb event • Ability to perform precise measurements • Lowest possible amount of material (tracking region) 30% X0 • Impact parameter and vertex resolution z = 45 m on interaction point • B proper time resolution 40 fs • B mass resolution 15 MeV/c2 • Particle identification (e.g. K/ separation) • Very selective and efficient multi-level triggerfor interesting B decays (L0 hardware & L1, HLT software) 16 MHz  1 kHz (so 1/16’000) • Huge dataset handling, large scale computing(distributed analysis, GRID, …) 21010 evts/year * 100 kB/evt = 2 PBytes per year Meeting of EPFL Research Commission

  11. Pre-cursor ideas Expressions of interest LHCb dipole magnet installed in cavern viewed along beam line towards interaction point LHCb collab. formed Letter of Intent R&D Prototypes Technical Proposal & CERN approval Technical Design Reports ~ 4 m Construction 1990 1993 1998 2000 LHC startup 1st physics paper 1995 Data taking Analyses Publications (physics results) Fe yoke (1.45 kt) Al coil (2  25 t) 2002 4.2 MW power at 1 T field 2004 2007 2010 2015 ? We are here LHCb now in construction phase Detector construction underway: – Installation until end 2006 – Commissioning in 2007 until LHC beam (summer) Meeting of EPFL Research Commission

  12. LHCb collaboration • ~500 scientists, 45 institutions, 13 countries • Memoranda of Understanding: • construction, M&O, computing • Constitution (defining organisation) • Organization • Collaboration board (one member/institution) • Management: • spokesperson, technical coordinator, resources coordinator • Project leaders: • different sub-detectors, trigger, physics, reconstruction, software, computing, … • Coordinators: • electronics, test beam, coordination panels • Monitoring, imposed and controlled by CERN • LHC committee (scientific and technical review) • Resources Review Board Two Swiss institutes:EPFL and UniZH Prof. Tatsuya Nakada (EPFL), spokesperson since 1995, recently re-elected for a new term until Feb. 2008 Prof. Ueli Strauman (UniZH),Si tracker project leader Prof. Olivier Schneider (EPFL),physics project leadersince 2000 Gérald Parisod, RRB member Meeting of EPFL Research Commission

  13. 1999 CERN 2000 CERN, France, Romania, Russia, Spain, Ukraine 2000 CERN, Italy, UK 2001 Brazil, CERN, Italy, Russia 2001 CERN, Germany, Netherlands, Switzerland, UK, Ukraine 2001 China, GermanyNetherlands, Poland 2001 CERN, China, France Switzerland, UK 2002 Germany, Spain Switzerland 2003 2003 Brazil, CERN, France, Italy, Poland, Switzerland, UK 11th TDR on on computing due in 2005 Technical Design Reports Meeting of EPFL Research Commission

  14. LPHE’s responsibilities in LHCb VELO line adaptor • VELO and readout electronics: Prof. A. Bay • Development of an off-detector electronics board for the VELO became a global project within LHCb for (almost) all detectors:TELL1, coordinated by A. Bay (final R&D and production) • Transmission lines and power supplies for the VELO • Inner Tracker: Dr. Minh-Tam Tran • R&D and construction of tracking stations downstream of the magnet, close to the beam pipe (Si detectors):ladder assembly & bonding, mechanics, cooling, … • TELL1 and Inner Tracker maintenance and operations (during commissioning and several years of data-taking) • Trigger and physics: SNSF Prof. T. Schietinger & Prof. O. Schneider • Monte Carlo performance studies and overall detector optimization • Development of software trigger algorithms (L1, HLT) and physics reconstruction algorithms Need to rely on our electronics and mechanics workshops Inner Tracker gluing jig Meeting of EPFL Research Commission

  15. VELO Vertex locator analogue links Inner Tracker (Si detectors) LPHE’s construction commitments Off-detector electronics "TELL1" Meeting of EPFL Research Commission

  16. Inner tracker • Design: • 3 stations (T1, T2, T3) • 4 boxes per station • 4 Si planes (xuvx) per box • 504 Si sensors • Si strip pitch 198 m • 129’024 detection channels • 1008 Beetle readout chips with analog pipeline (L0 buffer, 4 s) • Big issue: minimize material • Construction: • EDR in Dec 2004 • Start construction early 2005(assembly in Lausanne and CERN) • Installation finished end 2006 ~ 6 m  4.5 m readout connectors Be beam pipe 320 mm Si 410 mm Si 5C ~130 cm  45 cm C6F14 coolant(–15C) Meeting of EPFL Research Commission

  17. Pre-processor FPGA L1 buffer (58 ms, 58 kevts) 1 MHz Optical or analog interfaces  Fully developed at LPHE Credit-card PC L0 “yes”  Experiment control system Font-end (on-detector) electronics  clock  40 kHz Optical or analog interfaces L1 “yes”  L0 “yes” CPU farm (~1800)  to L1 Gigabit ethernet interface to HLT  Sync & link FPGA  HLT “yes” storage TELL1 readout board Final design ready ~300 boards to be built for LHCb Meeting of EPFL Research Commission

  18. – • Bs–Bs oscillation frequency: ms  |Vts|2 0 0 Vts Vts Expected unmixed BsDs sample in one year of data taking (fast MC) Physics performance study (example) Full MC • Very interesting measurement to be done with 1st year of data • Needed for the observation of CP asymmetries with Bs decays Fast Bs oscillation, proper-time resolution crucial 0 After 1 year, can observe5 signal if ms < 68 ps1 well beyond SM prediction Meeting of EPFL Research Commission

  19. CP Summary • CP: • fundamental (a)symmetry of nature (matter vs antimatter) • cosmology calls for CP violation beyond Standard Model • LHCb: • will exploit LHC’s huge b-hadron production to measure precisely CP violation and search for New Physics • detector R&D finished, construction started • data-taking as soon as LHC turns on (2007) • LPHE @ EPFL: • plays a leading role in LHCb collaboration • responsible for crucial parts of the detector 40 years after its discovery in 1964, CP violation may still reveal secrets about its origin. We hope it will be the case in LHCb. Meeting of EPFL Research Commission

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