No Slide Title

Prospects for

at LHCbWilliam ReeceImperial College LondonPhysics at the LHC, 3rd October 20081IntroductionWilliam Reece - Imperial College LondonPage 2FCNC quark transitions occur via a loopNew physics (NP) can enter the loopTreat with Operator Product ExpansionModel independent approach

Wilson Coefficients give short range PhysicsMeasure to discover or exclude entire classes of NP

William Reece - Imperial College LondonPage 3 First observed at Belle Particles in LoopBoth neutral and charged NP(replace W, Z0/g, u/c/t)Sensitive to NPDominated by C7, C9, C10Studied with NP from SUSY,Littlest Higgs, Randall-Sundrum,Universal Extra Dimensions etcLaboratory for Studying NPComplementary to direct searchesOffers NP model discriminationfor any LHC discoveriesO7gO9,10Need to go pretty quickly here3William Reece - Imperial College LondonPage 4Decay KinematicsDecay in terms of 3 Angles and 1 Invariant Massl, K, f and q2, the invariant mass squared of m pairSee e.g. arXiv: 0807.2589What to Measure?

Angular observablesSmall theory errorExperimentally accessibleE.g. forward-backward asymmetry of mmSensitive to interferencebetween C7, C9 & C10Plausible NP models Large deviationsZero crossing point (q20)Accessible with small integrated luminosities (~0.5fb-1)Form factors cancelat leading order

William Reece - Imperial College LondonPage 5Ali et al, PR D61:074024 (2000)SMq2 (GeV2)AFBC7 = -C7SMC10 = -C10SMThe solid line denotes the SM prediction. The dotted (long-short dashed) lines correspond to the SUGRA (the MIA-SUSY) model, using the parameters given in Eq. (6.4) (Eq. (6.10)) with the upper and lower curves representing the C7 e < 0 and C7 e > 0 case, respectively. The dashed curves indicating a positive asymmetry for large s correspond to the MIA-SUSY models using the parameters given in Eq. (6.11), i.e. the best depression scenario with C> 0.5Current Status Interesting Hints? William Reece - Imperial College LondonPage 6

FL longitudinal polarization of the K*

Belle 657 BB PairsBaBar 384 BB PairsBelle (2008) - ICHEPBaBar (2008) 0804.4412Opposite sign convention w.r.t. LHCbThe color scheme is the same for all the plots

Plots of our results for AFB and Fl for the decay BK + showing comparisons with SM (solid); C7=C SM 7 (longdash); C9C10=C SM 9 C SM 10 (short-dash); C7 =C SM 7 ,C9C10 =C SM 9 C SM 10 (dash-dot). Statistical and systematic errors are added in quadrature. Expected FL values integrated overeachq 2 region are also shown. The FL curves with C9C10 =C SM 9 C SM 10 are nearly identical to the two curves shown6Current Status Zooming In William Reece - Imperial College LondonPage 7

Belle (2008) - ICHEPBaBar (2008) 0804.4412Observables only reliably calculable in q2 region 1-6 GeV2/c4Up to LHCb to see what is really going on!(SM + Errors from arXiv: 0807.2589)BaBar (2008) ~100 events, Belle (2008) ~ 200 eventsLess than 0.1fb-1 will give same statistics as currently availableLHCb (2fb-1) ~ 7.2k eventsAFBFL

Selecting the Signal at LHCbChallenging EnvironmentLHCb Optimized for B-physicsL0 m triggerm pT threshold ~ 1GeVBd vertex res. ~130mmTrack momentum ~0.5%Bd mass res. ~ 18 MeVGood m ID performance keyp/K separation from RICHs

William Reece - Imperial College LondonPage 8

Signal YieldsLatest full MC studies:Total selection eff. 1.1%~7.2k per 2fb-1 (full q2 range)~3.7k per 2fb-1 (q2 < mJ/y2)~1.1k of background eventsSee CERN-LHCb-2007-038Use multivariate techniquesBd flight distance, IP,PID likelihoodsWilliam Reece - Imperial College LondonPage 92 fb-1 is the expected integrated luminosity for one nominal year of smooth LHCb data takingDominated by genuine m from BdLittle m mis-ID in MC dominant contributionSymmetric in ql, scales AFB observed significantAsymmetric in ql, affects AFB Non-resonantthought to be smallLimits set from Will measure in data

Background at LHCbWilliam Reece - Imperial College LondonPage 10

No. of Eventsbackground from:b + c, cbackground from:bm bmNo. of Eventsql / radql / radAFB first can do a counting experimentZero crossing also accessibleCERN-LHCb-2007-039Perform fits to decay angles FL, AT(2)Fit just to ql or all three anglesCERN-LHCb-2007-057Full angular analysisMany observables + improved resolutionSteps limited by understanding not statistics

Analysis Timeline (2fb-1 means 1 nominal year!)William Reece - Imperial College LondonPage 110.5 2 fb-12 4 fb-13 10 fb-1Counting Experiments for AFBCan extract AFB by countingforward and backward mRelatively simpleRequires only small integratedluminosityAllows zero-crossing extractions(q20) ~ 0.8 GeV2/c4 (0.5 fb-1), 0.5 GeV2/c4 (2 fb-1)

William Reece - Imperial College LondonPage 12s(q20) a AFB gradientBinned in q2Simple CountingUnbinned in q2Beyond SimpleCountingFind AFB frompolynomials

Useful cross-checkbetween methods+ more robustFit polynomialsHere I need to present the two methods as being a useful cross-check for each other. The binned approach will be easier to calibrate, but the unbinned approach will produce slightly better results once the systematics have been understood.12

SM input+ errors

Three decay angles beyond ql Angular projections of ql, f, qK dist.

Perform simultaneous fit in q2 binsImprove precision on AFB by ~2FL precision also improvedMeasure new observable AT(2)with poor resolution in 1-6 GeV2/c4region due to (1-FL) suppressionProjection Fits[CERN-LHCb-2007-057][Lunghi et al, JHEP 0704 (2007) 058]LHCb 2fb-1 BaBar Belle 08William Reece - Imperial College LondonPage 1313Full Angular Analysis parameterized byK* spin amplitudes Perform fit for amplitudesAssume polynomial q2 variationCalc. observables from amplitudesNew observables AT(3) AT(4)

10fb-1 sensitivities for SUSY inputJHEP 0704 (2007) 058 model bMC Fits converge with 2fb-1Acceptance a challengeWilliam Reece - Imperial College LondonPage 14CERN-LHCb-2008-041arXiv 0807.2589SM Theory DistributionToy fits to SUSY model b (C7 != 0) 1, 2s LHCb 10fb-1Finding NP in C7William Reece - Imperial College LondonPage 15AT(3) TH + LHCb 10fb-1AT(4) TH + LHCb 10fb-1Egede, Hurth,Matias, Ramon,WR. PreliminarySMAllowed regions - C7 realJHEP 0807:106,2008After 10fb-1 FA analysis?(0.083,-0.21)Summary Excellent prospects for discovery of NPHints from B-factories + theoryExpect 7.2k signal events per yearover whole q2 rangeExciting Physics programMany observables to studyCounting experiments, projections, full angularReal discriminating power for NPExciting times ahead!William Reece - Imperial College LondonPage 16Back UP SlidesWilliam Reece - Imperial College LondonPage 17

Acceptance Effects for AFB

ql/radqK/radq2/GeV2Efficiency e / a.u.Efficiency e / a.u.Efficiency e / a.u.Efficiency e / a.u.Efficiency e / a.u.Efficiency e / a.u.q2/GeV2q2/GeV2q2/GeV2q2/GeV2q2/GeV2q2/GeV2AFBAFBAFBe backwarde forwarde backwarde forwarde backwarde forwardInputoutputIn all cases, no bias on 0-ptTake toy efficiencies for q2, ql, qKqK biases AFB even though are only using ql directlyOutside the Theoretically Clean RegionB Vector form factors large source of theoretical uncertaintyDominated by low energy effects7 independent functions of q2 V, T1,2,3, A0,1,2 Use SCET to reduce 7 2 at Leading OrderOnly valid in range 1-6 GeV2/c4Can not handle resonances or low q2 regionObservables where 2 remaining FF cancelAT(2,3,4) and AFB zero-crossing pointUncertainties outside region much greaterSee Beneke et al, Nucl. Phys. B612 (2001) 26-58William Reece - Imperial College LondonPage 19Projection Fit ResolutionsResults from CERN-LHCb-2007-057William Reece - Imperial College LondonPage 20ObservablesWilliam Reece - Imperial College LondonPage 21

Drell-Yan BackgroundsNot significant background at LHCbFull simulation study: decays dominant source of mm in mass rangeDrell-Yan production much lowerReconstruction Efficiency:Fake signal need a K* from elsewhereWrongly associate this with mm vertexMiss-ID rate should be very low

William Reece - Imperial College LondonPage 22NP in C7 LegendWilliam Reece - Imperial College LondonPage 23

Selection Cuts from LHCB-2007-038William Reece - Imperial College LondonPage 24

Angular DistributionWilliam Reece - Imperial College LondonPage 25

Physics Sensitivity to K* Spin AmplitudesWilliam Reece - Imperial College LondonPage 26

Experimental Constraints for C7 PlotWilliam Reece - Imperial College LondonPage 27

Bd K0+

b s

Heff = 4GF2VtbV

ts

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= mb

P. Koppenburg

Operators

Effective HamiltonianHA(MF ) = F |Heff|M

Heff = 4GF2V tsVtb

10i=1

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OperatorsOi: Long-distance effects Wilson coefficients Ci: Short-distance ef-fects(masses above are integrated out)

New physics can show up in new operators or modi-

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Operator

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Overview of Rare Decays at LHCb 26/09/07 LHCb-UK in Durham p.3/16

P. Koppenburg

Operators

Effective HamiltonianHA(MF ) = F |Heff|M

Heff = 4GF2V tsVtb

10i=1

Ci()Oi()

OperatorsOi: Long-distance effects Wilson coefficients Ci: Short-distance ef-fects(masses above are integrated out)

New physics can show up in new operators or modi-

fied Wilson coefficients

Operator

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g

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s

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Overview of Rare Decays at LHCb 26/09/07 LHCb-UK in Durham p.3/16

Br(Bd K0+) = (1.22+0.380.32) 106

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in 2 fb1 of data (Assuming the SM BRof 12 107):

Sample Yield

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2(b ) 1050 250

b c(q) 600 200

Background 3700 300

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