The LHCb experiment at Cern

Transcription

1 The LHCb experiment at Cern Olivier Leroy 5 Sep 2017 Introduction of the CPPM-LHCb group, M2 P3TMA O. Leroy The LHCb experiment 5/9/ / 15

2 Outline 1 Introduction 2 Searching for New Physics in Flavor Physics 3 The LHCb detector at the LHC 4 The CPPM LHCb activities 5 Conclusions O. Leroy The LHCb experiment 5/9/ / 15

3 Introduction to LHCb WHAT? LHCb: experiment installed on the LHC, the world largest particle accelerator, at Cern in Geneva. International collaboration gathering 1100 physicists WHY? Search for Beyond the Standard Model physics, studying properties of beauty and charm hadrons HOW? Compare precise theoretical predictions to precise experimental measurements. Detector dedicated to precision heavy flavor physics: ability to select wide range of heavy flavor decays, to measure seconds lifetimes, to separate kaons from pions,... O. Leroy The LHCb experiment 5/9/ / 15

4 The Standard Model Many un-answered questions: Why 28 free parameters? Why 3 families? Mass hierarchy 8 orders of magnitude!? Where is antimatter? Dark matter? Dark energy? O. Leroy The LHCb experiment 5/9/ / 15

5 Searching for New Physics Fundamental questions: Hierarchy of masses and mixing angles? why 3 generations? Stability of the Higgs mass? Dark matter? Baryon asymmetry of the Universe requires CPV beyond the SM (Not necessarily in flavor changing processes, nor necessarily in quark sector) Two ways to address them: Direct searches: try to produce directly new real particles on-shell, but we don t know their mass or lifetime and we are limited by the center-of-mass energy of accelerator. Indirect searches: study the effect of off-shell (virtual) particles. Compare precise theoretical predictions with precise experimental measurements. Not limited by the center-of-mass energy of accelerator. e.g. Argus 1987, B 0 B 0 mixing heavy top quark Flavor physics exploits the second approach O. Leroy The LHCb experiment 5/9/ / 15

6 The Large Hadron Collider LHC 27 km in circumference Center-of-mass energy: 13 TeV Proton-proton collisions > 40 millions times per second O. Leroy The LHCb experiment 5/9/ / 15

7 The LHCb detector Unique features: Real time selection of collisions with beauty or charm content Exceptionally good resolution on particle time of flights Separation pions / kaons O. Leroy The LHCb experiment 5/9/ / 15

8 The LHCb Collaboration physicists from 73 institutes and 16 countries O. Leroy The LHCb experiment 5/9/ / 15

9 LHCb at CPPM Permanent physicists: Elie Aslanides Julien Cogan Renaud Le Gac Olivier Leroy (group leader) Giampiero Mancinelli Justine Serrano Postdocs: Andrey Tayduganov (B K 0 τ τ ) + one newcomer this Autumn PhD students: Morgan Martin (CP violation) Joan Arnau (B τ µ) Cédric Méaux (B τ τ ) O. Leroy The LHCb experiment 5/9/ / 15

10 Two intriguing anomalies in Flavor Physics Nowadays, the 2 largest deviations with respect to the Standard Model expectations are observed in flavor physics, both at the 4σ level: charged current b cτν τ (R D, R D ) neutral current b sll (R K, R K, P 5,...) Anomalies linked to Lepton Flavor Universality (e, µ, τ) If measured central value do not change, LHCb can transform these hints into discoveries with the data of the ongoing Run 2! ( ) O. Leroy The LHCb experiment 5/9/ / 15

11 Charged current anomalies b cτν τ R(D) B(B0 D τ + ν τ ) B(B 0 D l + ν l ), R(D ) B(B0 D τ + ν τ ) B(B 0 D l +, l {µ, e} ν l ) SM = ± 0.008, SM = ± R(D*) 0.5 BaBar, PRL109,101802(2012) Belle, PRD92,072014(2015) LHCb, PRL115,111803(2015) Belle, PRD94,072007(2016) Belle, PRL118,211801(2017) LHCb, FPCP2017 Average 2 χ = 1.0 contours SM Predictions R(D)=0.300(8) HPQCD (2015) R(D)=0.299(11) FNAL/MILC (2015) R(D*)=0.252(3) S. Fajfer et al. (2012) σ 4σ Different experiments, techniques, channels ALL above SM LHCb, Belle and BaBar combination: 4.1σ away from SM! Hint for Lepton Flavor Non Universality? HFLAV FPCP 2017 P(χ 2 ) = 71.6% R(D) O. Leroy The LHCb experiment 5/9/ / 15

12 Neutral current anomalies b sll Several measurements involving b sll, (l = µ, e) deviate from their SM expectation (2 3σ) R K = B(B + K + µ + µ )/B(B + K + e + e ), R K, BR de B 0 K µ + µ, B 0 s φµ + µ, Λ b Λ 0 µ + µ, P 5 The combined effect of these small deviations point towards the same direction: C9 NP µ = 1, implying violation of the leptonic universality µ e. Significance of global fits 5σ arxiv: Deficit of muons? Theoretical uncertainties or experimental? μ μ arxiv: O. Leroy The LHCb experiment 5/9/ / 15

13 Test of Lepton Flavor Universality at CPPM We are studying both these anomalies at CPPM: 1 Study of neutral anomalies b sll: B ττ, B K 0 ττ Test of the Lepton Number Violating decay B τµ B 0 s b s W u, c, t u, c, t γ, Z 0, H 0 τ + B 0 s τ b s Z τ + τ 2 Study of charged anomalies using B 0 D τ + ν τ In the long term, not only we may discover NP, but also discriminate various scenarios thanks to: Different spins (0, 1/2, 1) in the final state B + D ( )0 τ + ν τ, B 0 D τ + ν τ, Bs 0 D ( ) s τ + ν τ, B c + J/ψ τ + ν τ, Λ b Λ ( ) c τ + ν τ,... Different observables: BR, τ polarization, angles, BR(q 2 ) O. Leroy The LHCb experiment 5/9/ / 15

14 Exciting prospects for a PhD b sll ( ) transitions with a τ lepton in the final state the 3rd family is still poorly known important measurements in the context of the current anomalies experimentally very challenging, pioneer studies Strong expertise at CPPM : B (s) τ( 3πν)τ( 3πν) : Run1 - best limits on BR - published B (s) τ( 3πν)τ( µνν) : Run1 and Run2 - on going thesis B (s) τ( 3πν)µ (LFV!) : Run1 and Run2 - on going thesis Other important decays to address : B (s) K ττ (in progress) B (s) K ττ B (s) K τµ Plenty of room to contribute! O. Leroy The LHCb experiment 5/9/ / 15

15 Conclusions LHCb is a big experiment installed on the world largest particle accelerator LHC at Cern in Geneva. The CPPM is involved in LHCb since its beginning (1998) We contributed to its construction, we are currently taking data, analyzing them and preparing the upgrades phases scheduled after We are working on two 4σ intriguing anomalies, in the charged b cτν τ and neutral currents b sll You are welcome to make your interships with us or simply come and discuss! Olivier.Leroy@in2p3.fr O. Leroy The LHCb experiment 5/9/ / 15

16 Backups O. Leroy The LHCb experiment 5/9/ / 15

17 Matter - antimatter Matter and animatter do not behave exactly the same way We measure it! But the measured asymmetry is too small to explain the disappearence of antimatter at the Universe scale O. Leroy The LHCb experiment 5/9/ / 15

18 Planning LHC 2035 O. Leroy The LHCb experiment 5/9/ / 15

19 Hardware/Software contributions - LHCb CPPM We are responsible for DIRAC, the World Wide distributed computing grid middle-ware We have designed and constructed the level-0 muon trigger We are responsible for the 500 electronic read-out boards for the upgrade phase (2019) We already prepare the next steps (2030) with possible contributions to the fast data acquisition and/or to the vertex detector O. Leroy PCI40 module at different production steps The LHCb experiment 5/9/ / 15