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LHCb status and plans

LHCb status and plans. Roger Forty (CERN) on behalf of the LHCb Collaboration. LHCb status Physics highlights Plans. Physics at the LHC, Vancouver, 4–9 June 2012 . 1. LHCb status. LHCb is the dedicated flavour physics experiment at the LHC

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LHCb status and plans

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  1. LHCb status and plans Roger Forty (CERN) on behalf of the LHCb Collaboration LHCb status Physics highlights Plans Physics at the LHC, Vancouver, 4–9 June 2012

  2. 1. LHCb status • LHCb is the dedicated flavour physics experiment at the LHC • ATLAS & CMS search for the direct production of new states LHCb is designed to see their indirecteffect on charmand beautydecays via virtual production in loop diagrams: • Such an indirect approach can be very powerful: e.g. B0–B0 mixing discovered at ARGUS (1987) → top quark unexpectedly heavy: m(t) > 50 GeV/c2 • Key topics for LHCb include: to check whether CP violation is due to a single phase in the quark mixing (CKM) matrix, as in the Standard Model Study rare decays: FCNC decays (e.g. Bs→m+m-) are strongly suppressed in SM, may be enhanced by Supersymmetry, or other new physics e+e- (4S)  B0B0 LHCb status and plans

  3. Forward spectrometer 10 – 300 mrad p p • Forward-peaked B production → LHCb is a forward spectrometer (operating in collider mode) • bb cross-section = 284 ± 53 mbat the LHC (s = 7 TeV) [PLB 694 209] →~ 100,000 bb pairs produced/second (104B factories) Charm production factor ~20 higher! [PYTHIA] See talk of Marco Adinolfi [CONF-2010-013] LHCb status and plans

  4. Advantages • Enormous production rate  have overtaken B factories even for B0 and B+ decays • BR(B+ p+m+m-)= (2.4±0.6stat±0.2sys)×10-8Previous limit < 6.9×10-8(Belle PRD 78 011101)Rarest B decay ever observed! • All b-hadron species are produced at the high energy of the LHC • New states discovered e.g.Lb*(5912/5920) orbitally-excited states • New decay modes discovered e.g.Bc+ J/yp+p-p+ • Bsphysics is rich and little explored • Large boost: B decay lengths ~ O(1cm) • Complementary coverage for other physics • Electroweak, QCD, exotics, … [CONF-2012-006] W± charge asymmetry vsh Lb* [arXiv:1205.3452] [CONF-2011-039] Bc+ B+ p+m+m- [arXiv:1204.0079] ATLAS/CMS LHCb William Barter & Marianna Fontana LHCb status and plans

  5. Collaboration 804 16 55 Muondetector RICH Magnet VELO Calorimeters Tracker Added since PLHC-2011: Birmingham, Cincinnati, Lahore, Rostock LHCb status and plans

  6. Tracking performance • Dipole magnet, polarity regularly switched to cancel systematic effects • New this year: beam optics changed to decouple crossing angles from LHC (V) and spectrometer magnet (H) • Momentum resolution:Dp/p = 0.4 – 0.6 % (5–100 GeV/c) Real data! Beam optics at interaction point Bs J/y f [CONF-2012-002] • s(mB) = 8 MeV/c2 cf ~ 16 MeV/c2[CMS DPS-2010-040]22 MeV/c2[ATLAS CONF-2011-050] LHCb status and plans

  7. Vertex detection • VELO (Vertex Locator)21 modules of r-f silicon sensor disksRetracted for safety during beam injection • Reconstructed beam-gas vertices (used for luminosity measurement) • Impact parameter resolution ~ 20 mmProper-time resolution: st = 45 fscf CDF: st = 87 fs[PRL 97 242003] r z Beam Prompt J/y Bs J/y f VELO sensors 7 mm [CONF-2012-002] • [PLB 693 69] Beam 2 Beam 1 LHCb status and plans

  8. Particle identification RICH-1: dual radiator • Charged hadrons identified with two Ring-imaging Cherenkov detectors covering 2 < p < 100 GeV/c • Hybrid Photon Detectors (HPDs) 500 tubes each with 1024 pixelsHigh efficiency, low noise • New this year: gas-tight box for aerogelto avoid contamination by C4F10 gas Allows strong suppression ofcombinatorial background inhadronic decays e.g.f  K+K- RICH-1: dual radiator Without RICH With RICH eKK> 90% for epK< 5% LHCb status and plans

  9. Calorimeters + Muon Bs→ f g • ECAL: ShashlikPb-scintillators(E)/E = 10% /√E 1% • HCAL: Tile Fe-scintillatorallows triggering on hadronicfinal states • Muon system: 5 stations MWPCs/Fe [arXiv:1202.6267]  m+m- GiacomoGraziani [arXiv: 1202.6579] LHCb status and plans

  10. Data taking pp collisions/crossing (25ns) • Nominal LHCb luminosity = 2 ×1032 cm-2 s-1Precision physics depending on vertex structure:easier in a low-pileup environment • Continuous (automatic) adjustment of offset of colliding beams allows luminosity to be levelledThanks to LHC team for excellent collaboration! • Data taken with high efficiency > 90%Offline data quality rejects < 1%Detectors all with > 98% active channels 2011 2012 LHCb 2011 was a fantastic year! L dt= 1 fb-1 (used for most results shown here) ~ 30×more data than at PLHC-2011 Data taking in 2012 at 4 ×1032 cm-2 s-1~ 0.4 fb-1 integrated so far LHCb status and plans

  11. Data processing Output rate of single server vs time Detector • Trigger in two steps: Level-0 in hardware pT of e, m, and hadron(thresholds ~ 1–3 GeV) reduce rate to 1 MHz • Then all detectors read out into large CPU farm (~1500 servers) High Level Trigger in software • New this year: • Output rate increased to 4.5 kHz to provide data sample for analysis during shutdown(events are relatively small ~ 60 kB) • Deferred triggering: fraction of events writtento local storage of CPUs and processed during inter-fill gap ~10% increase in effective power • O(1010) events recorded per year: centralized “stripping” selection to reduce to samples of < ~107 events for individual analysis:~ 800 selections! 4.5 kHz Storage LHCb status and plans

  12. 2. Physics highlights • 56 physics publications to date, more in pipeline > 80 preliminary results submitted as Conference Papers [LHCb-CONF-xxx]all available at www.cern.ch/lhcb • Can only give a selective taste of LHCb’s physics output— for the full feast see the contributed talks and posters • Tagging of production flavour (B/B) important for mixing & CP analysesPerformance calibrated using control channels such as B+→ J/yK+ • Tagging power: eeff = e(1-w)2determined from mixing signals • eeff = (3.2 ± 0.8) % (Opposite side) Miriam Calvo Gomez (1.3 ± 0.4) % (Same side) [CONF-2011-050] LHCb status and plans

  13. Particle-antiparticle mixing • Studied for all neutral mesons B0 : now well-established • Bs0 : studied using Bs0  Ds+p- decays Dms = 17.725 ± 0.041 ± 0.026 ps-1(world-best)cf : 17.77 ± 0.10 ± 0.07 ps-1(CDF PRL 97 242003) • D0 : “wrong-sign” decays D0 K+p- measuredTime-dependent analysis in progress to separate mixing from DCS contribution D0 [CONF-2011-029] Right-sign B0 Bs0 [arXiv:1202.4979] [CONF-2011-050] Wrong-sign B0  D*-m+n LHCb status and plans

  14. CP violation Olivier Leroy • Phase of B0 mixing is well known: sin 2b = 0.67 ± 0.02[PDG] • Analogous phase in the Bs system is denoted fsExpected to be very small, precisely predicted: fs= -0.036 ± 0.002 rad (SM) • First Tevatron results hinted at large value (discrepancywith SM up to ~3s) • Golden mode for this study is Bs J/yf • VV final state: mixture of CP-odd and -even components separated using angular analysis [arXiv:1106.4041] Transversity angle distributions [CONF-2012-002] CP-even [LHCb-CONF-2012-002] CP-odd LHCb status and plans

  15. CPV in Bs mixing Sean Benson Results correlated with DGs = width difference of the Bs mass-eigenstates plotted as contours in (fsvsDGs) plane Ambiguous solution excluded by study of phase vs KK mass SM Update with 10× data Result presented at PLHC-2011 [arXiv:1202.4717] • LHCb result consistent with Standard ModelFirst significant direct measurement of DGs = 0.116 ± 0.018 ± 0.006 ps-1 • fs also measured in a second mode: Bs J/yf0Combined result: fs = -0.002 ± 0.083 ± 0.027 radStill room for new physics: increased precision required! [CONF-2012-002] LHCb status and plans

  16. CPV in B decays Daniel Johnson • Using the particle ID capability of LHCb, can isolate clean samples of the various decays that contribute to 2-body B →h+h-(h = p, K, p) • B0→K+p-: direct CP violation (in decay) clearly visible in raw distributions • Corrections required for detector and production asymmetriescontrolled using D0→K-p+, B0→ J/y K*0 samples: percent-level effects ACP = G(B0→K- p+) – G(B0→K+ p-) / sum = -0.088 ± 0.011 ± 0.008 in good agreement with world average: -0.098 ± 0.012 Bs →p+ K- Bs →p- K+ • Adjusting the selectionto enhance the Bs →p+ K- contribution • ACP (Bs→p+ K-) = 0.27 ± 0.08 ± 0.02 • → First 3s evidence for CP asymmetry in Bs decays B0→K+ p- B0→K- p+ [PRL 108 201601] 0.011 LHCb status and plans

  17. Rare decays Mitesh Patel Bsm+m- candidate • Bsm+m- strongly suppressed in SMPredicted BR = (3.2 ± 0.2)  10-9*very sensitive to new physics • Analysis based on multivariate estimator (BDT, combining vertex and geometrical information) & dimuon mass Mmm • Their distributions calibrated using data: B → hh and dimuon resonances • World-best limit set:BR < 4.5 × 10-9 (at 95% CL)cf< 7.7 × 10-9(CMS arXiv:1203.3976)< 22 × 10-9(ATLAS CONF-2012-010) • Sensitivity (slightly) greater than CMS from 5 less integrated luminosity* Experimental BR is time-integrated, so prediction should be scaled by ×1.1 for comparison [arXiv:1204.1737] Mmmin sensitive region of BDT [JHEP 1010 009] Setting limit on BR [arXiv:1203.4493] CosmeAdrover mmm = 5.357 GeV, BDT = 0.90, Decay length = 11.5 mm Tracks shown for pT > 0.5 GeV LHCb status and plans

  18. Rare decays Mitesh Patel • Bsm+m- strongly suppressed in SMPredicted BR = (3.2 ± 0.2)  10-9* very sensitive to new physics • Analysis based on multivariate estimator (BDT, combining vertex and geometrical information) & dimuon mass Mmm • Not enough candidates to providesignificant measurement of BR • World-best limit set:BR < 4.5 × 10-9 (at 95% CL)cf< 7.7 × 10-9(CMS arXiv:1203.3976)< 22 × 10-9(ATLAS CONF-2012-010) • Large enhancement of BR relative to SM expectation is ruled out * Experimental BR is time-integrated, so prediction should be scaled by ×1.1 for comparison [arXiv:1204.1737] Mmmin sensitive region of BDT [JHEP 1010 009] Setting limit on BR [arXiv:1203.4493] CosmeAdrover LHCb status and plans

  19. B0 K*m+m- CosmeAdrover [arXiv:1101.0470] • Rare decay viab→s penguin: • Forward-backward asymmetry sensitive to modification of the helicity structurePrevious results hinted at discrepancy • LHCb has largest sample in the world: 900 events, as clean as the B factories! • Zero-crossing point precisely predictedq2 (AFB= 0) = 4.0 – 4.3 GeV2/c4 • First measurement: 4.9 +1.1 GeV2/c4Earlier discrepancies not confirmed • However, evidence seen for different BR between B+ K+mm& B0 K0mm modes ( Additional slides) SM [CONF-2012-008] -1.3 LHCb status and plans

  20. Impact of results • LHCb results provide strong constraints on possible models for new physicsComplementary to the direct searches at ATLAS/CMS • Recent examples: limit on Bsm+m-constraining SUSY at high tan band combination of Bsm+m-and fs restricting various models: [N. Mahmoudi, Moriond QCD] [D. Straub, arXiv:1107.0266] Direct exclusion(CMS 4.4 fb-1) Bsm+m-(LHCb1fb-1) • And then something unexpected… (fs) LHCb status and plans

  21. CPV of charm Silvia Borghi • Expected to be small in the SM (< 10-3) • Enormous statistics available: >106 D0 K+K- from D*+ D0p+Charge of p from D* determines D0 /D0 • DACP = difference in CP asymmetry for D0  K+K- and D0  p+p- Robust: detection and production asymmetries cancel (at first order) DACP = (-0.82 ± 0.21 ± 0.11)% Zero CPV is excluded at 3.5 s • Before the LHCb result: “CP violation…at the percent level signals new physics” [Y. Grossman, arXiv:hep-ph/0609178] (and many others) After: “We have shown that it is plausible that the SM accounts for the measured value… Nevertheless, new physics could be at play”[J.Brodet al, arXiv:1111.5000] D0 K+K- 1.4 × 106 signal [PRL 108 111602] LHCb LHCb status and plans

  22. 3. Plans • New physics has not yet shown itself clearly at the LHC • Essential to improve measurements of precisely-predicted quantities: fs, BR(Bs→ m+m), q2 (AFB= 0) … Another example: the CP-angle gis the least well measured UT angle (depends on rare b→u decays)Uncertainty 10–12º [UTfit/CKMfitter] • Clean determination using B  DK tree decays with theoretical uncertainty < 1º • First constraints already achieved:Can profit from much higher statistics long term programme at LHCb g (rad) [PLB 712 203] Daniel Johnson & Sean Benson rB LHCb status and plans

  23. LHCb upgrade Silvia Borghi • Expect to double data-set by end of this yearAfter long shutdown, further doubling of data-set in 2015–17 (plus increase of cross-sections with higher energy): total of 5–7 fb-1 • Main limitation that currently prevents exploiting higher luminosity is the hardware trigger: keeping output rate < 1 MHz requires raising of thresholds  hadronic yields reach plateau: • Propose to remove the hardware trigger Read out LHCb at 40 MHz crossing rateFlexible software trigger in CPU farm increase in yields by factor 10–20 at 1–2 ×1033 cm-2 s-1 (25 ns is required) • Requires replacing front-end electronicsPlanned for the long shutdown in 2018Running for ~10 years will give 50 fb-1 → General-purpose detector for the forward region LHCb status and plans

  24. Detector modifications • Baseline detector modifications to allow 40 MHz readout e.g. Scintillating-fibretracker R&D on possible detector upgrades TORCH time-of-flight Pixel VELO LHCb status and plans

  25. Upgrade status • Letter of Intent for upgrade submitted to LHCC last year Encouraged to proceed to Technical Design Report • Framework TDRjust submitted (25 May) schedules & cost of subsystems, and institute interests • Update of physics case and expected performance: [LHCC-2012-007] Timeline (tight!) Letter of Intent Framework TDR R&D ongoing Subsystem TDRs 2014-16 Tender & prodn 2017 Acceptance testing Installation Data taking LHCb status and plans

  26. Conclusions • LHCb taking data with high efficiency and excellent detector performance • Luminosity above design, 1.4 fb-1 recorded so far • Excellent mass and decay-time resolution, particle ID, etc. • World-best measurements of many physics parameters • Dms, DGs, fs, BR(Bsm+m-), masses, lifetimes, etc.First observations of new decays, evidence for CP violation of Bs • So far almost all are in good agreement with the Standard Model → strong constraints on new physics in the flavour sector • Possible hints of physics beyond the Standard Model require further study: • Evidence seen for CP violation in charm, unexpected • Isospin asymmetry for B → Km+m- is also puzzling • Upgrade of LHCb in preparation for 2018: 10× yield + software trigger → Much more to come: new collaborators welcome! LHCb status and plans

  27. Additional slides • Signal for B0 → K∗0μ+μ- • SM prediction for isospin asymmetry AI of K∗μ+μ-[Feldmann &Maas, JHEP 01 074] • LHCb result: consistent with SM expectation in this mode[arXiv:1205.3422] AI (%) q2 (GeV2/c4) LHCb status and plans

  28. Isospin asymmetry • Compare B0 K0m+m- andB+ K+m+m- decays • Isospin asymmetry AIdefined as:G(B0 K0m+m-) -G(B+ K+m+m-)G(B0 K0m+m-) +G(B+ K+m+m-) • Expect AI~ zero in SM (< few %)Results from other experiments tended toward negative values • Previous discrepancy with SM is supported by new LHCb result: AI < 0 with over 4s significance • No asymmetry seen in closely-relatedB  K*m+m- mode (K*+  K0p+)No clear interpretation, so far [arXiv:1205.3422] LHCb status and plans

  29. g determination • Various methods usedInputs mostly from B factoriesgcomb = (75.5 ±10.5)° [UTfit] • Impact of LHCb results on the combination, for the ADS method (B+ → D0K+, D0 →K+p-)[D. Derkach, LHCb-TALK-2012-077] LHCb status and plans

  30. ASL • Strong interest in semileptonic (flavour-specific) asymmetry due to D0 result for dimuon asymmetry (comparing # of m+m+ and m-m- events)ASL = (−7.87 ± 1.72 ± 0.93) × 10−3[PRD 84 052007] (expect < 10-3 in SM) • Same approach difficult at pp machine due to production asymmetriesInstead use semileptonic decays, B(s) → D+(s) (K+K-p+) m-XResult from LHCb expected soon • Note: if ASLis large, expected to see large fs in most models Projected LHCb precision (statistical, 1 fb-1) [arXiv:0910.1032] LHCb status and plans

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