The LHCb experiment

Transcription

1 The LHCb experiment Julien Cogan Accueil M2 2014, Sept 9

2 Triumph of the Standard Model 2

3 Is it the end? Is it the end? Certainly not! Open questions pointing towards the existence of physics beyond the SM : Cosmological dark matter Baryon asymmetry of the Universe Non-zero (but small) neutrino masses quark and lepton masses hierarchical structure : 3

4 Beyond the Standard Model??? New degrees of freedom are expected at a scale Λ above the electroweak scale Which is the energy scale of New Physics (or the value of Λ)? Which is the symmetry structure of the new degrees of freedom(or the structure of the cn)? 4

5 Two natural paths to look for new physics Direct search (ATLAS & CMS) production of new particles (real) the more the new particles are heavy, the more energy is needed to produce them observation of their decay Indirect search (LHCb) Is there anything else beyond the SM at the TeV scale? virtual production of new particles heavy particles can be produced virtually (off mass shell) with moderate energy in the center of mass of the collision these virtual particles affect the decay processes differences w.r.t. standard model prediction What determines the observed pattern of masses and mixing angles of quarks and leptons? 5

6 The LHCb LHC CMS LHCb Atlas Alice LHCb : one of the 4 major experiments at LHC 6

7 The LHCb collaboration 934 members 65 institutes 17 countries 7

8 The LHCb physics program LHCb dedicated to precision measurements of heavy flavor : comparing precision measurements and clean predictions to find evidence for new physics flavor sector : very rich sector of the Standard Model (CKM mechanism, CP violation,...) with precise theoretical predictions 8

9 The LHCb physics program LHCb dedicated to precision measurements of heavy flavor : comparing precision measurements and clean predictions to find evidence for new physics flavor sector : very rich sector of the Standard Model (CKM mechanism, CP violation,...) with precise theoretical predictions Large measurements spectrum : B decay to charmonium Bs mixing, CPV B decay to open charm γ, B decay to double charm, rare hadronic B decay Rare decays leptonic, electroweak, radiative, LFV Charm physics mixing and CPV, charm production and spectroscopy Charmless B decay B h,h', B-> VV Semi-leptonic B decays search for CPV in mixing, form factors, rare decays B hadron and quarkonia Production and spectroscopy QCD, electroweak and exotica EW boson production, new long lived particles 9

10 The LHCb detector Typical topology : VErtex LOcator RICH detectors Calorimeters Resolve fast BS oscillation excellent vertex resolution Background reduction : very good impact parameter resolution good mass resolution good particle identification (K/π) Collect high statistics : efficient trigger for both hadronic and leptonic final states TRACKING system MUON system10

11 The LHCb detector Typical topology : Installation of the Vertex Locator VErtex LOcator RICH detectors Calorimeters Resolve fast BS oscillation excellent vertex resolution Background reduction : very good impact parameter resolution good mass resolution good particle identification (K/π) Collect high statistics : efficient trigger for both hadronic and leptonic final states TRACKING system MUON system11

12 The LHCb detector Typical topology : VErtex LOcator RICH detectors Calorimeters Resolve fast BS oscillation excellent vertex resolution Background reduction : very good impact parameter resolution good mass resolution good particle identification (K/π) Collect high statistics : efficient trigger for both hadronic and leptonic final states TRACKING system MUON system12

13 The LHCb detector Typical topology : VErtex LOcator RICH detectors Calorimeters Resolve fast BS oscillation excellent vertex resolution Background reduction : very good impact parameter resolution good mass resolution good particle identification (K/π) Collect high statistics : efficient trigger for both hadronic and Le trigger à muon de niveau 0 (CPPM) leptonic final states TRACKING system MUON system13

14 The LHCb detector specificities Acceptance in forward region maximize the acceptance for B decays complementary to ATLAS & CMS Run in low pile-up conditions lower instantaneous luminosity than ATLAS & CMS 14

15 Some recent LHCb results First observation of CP violation in the decay of Bs mesons (April 2013) Observation of an exotic particle Z(4430) [ccdu] (April 2014) Precise search for new physics (determination of the weak phase ФS - March 2013) B K*µµ : hint at new physics? (July 2013) B Kµµ/B Kee : breaking lepton universality? (σ=2.6) (July 2014) Observation of Bs μμ decays (CMS & LHCb - July 2013) And more to come... 15

16 LHCb plans and upgrade 2010 bunch spacing ECM LS1 50 ns 7 TeV TeV ns LS LS3 13 TeV 3 fb-1 > 5 fb-1 # of bunch crossings up to 1262 ~ 2622 (nominal) ℒ (cm-2s-1) ℒ 2019 > 5 fb-1 / year > fb-1 in less than 10 years LHCb upgrade 2015 : resume data taking - at higher energy - restart after 2 years!! 2018 : major upgrade of the LHCb experiment - full read-out at 40 MHz - increase instantaneous luminosity (get larger statistic) 16

17 CPPM

18 Le groupe LHCb au CPPM Members : 6 chercheurs 1 post-doctorant S. Akar 4 Doctorants E. Aslanides, J. Cogan, R. Le Gac, O. Leroy, G. Mancinelli, J. Serrano A. Morda et W. Kanso (2ème année) M. Martin (débute en octobre) 5 Ingénieurs permanents electronic : J-P. Cachemiche, F. Hachon, F. Réthoré temps réel : P-Y. Duval informatique : A. Tsaregorodtsev Main activities Technical level-0 muon trigger 40 MHz read-out (LHCb upgrade) grid middle-ware Participation to data taking (shift, piquet,...) Analysis very rare decays CP violation 18

19 Rare decays (1/2) Bs/d µµ SM : FCNC + helicity suppress very small branching ratio in the SM BR(Bs µµ) = 3.2±0.2 x 10-9 BR(Bd µµ) = 1.1±0.1 x Very sensitive to new physics contribution SM MSSM Recently measured at LHCb BR(BS µµ)= x10-9 Constraints on new physics models 19

20 Rare decays (2/2) Bs ττ less rare than B µµ : BR(BS ττ) 7 x 10-7 but can be largely enhanced by new physics very challenging experimentally τ is unstable (ex: τ πππν!!!) No experimental limit yet 20

21 Probing New Physics CP Violation With the start of LHC operation an exciting era in the search for N Physics has begun ΦS in BS J/Ψ Φ parameter sensitive to the interference between direct decay and decay after oscillation Direct searches Bs for new particles (ATLAS + CMS) J/ψφ Indirect searches (LHCb) _ Effect of virtualb particles in loop processes s New phases in loops! new sources of CP violation The LHC New Particles? Indirect searches can be powerful, e.g observation of BdNo mixing by ARGUS inyet 1985from pointedstandard to heavy top deviation model precision to be increased 21

22 Conclusion Flavor physics is a very active and exiting sector of the SM LHCb has taken the leader ship in this domain The CPPM group is involved in key LHCb measurements Data taking will resume shortly with a lot of new and exciting data to analyse! You are welcome to visit us... Contacts: R.Le Gac: legac@cppm.in2p3.fr O.Leroy: oleroy@cppm.in2p3.fr G.Mancinelli: giampi@cppm.in2p3.fr J.Cogan: cogan@cppm.in2p3.fr J.Serrano: serrano@cppm.in2p3.fr 22