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Y(5S): What has been learned and what can be learned

Y(5S): What has been learned and what can be learned. Introduction, and some B s Phenomenology Recent measurements at Y(5S) from CLEO & Belle B production studies B s rates: exclusive analyses B s rates: inclusive analyses Summary.

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Y(5S): What has been learned and what can be learned

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  1. Y(5S): What has been learned and what can be learned • Introduction, and some Bs Phenomenology • Recent measurements at Y(5S) from CLEO & Belle • B production studies • Bs rates: exclusive analyses • Bs rates: inclusive analyses • Summary Steven BluskSyracuse University(on behalf of the CLEO and Belle Collaborations)

  2. Introduction • The U(5S) discovered by CLEO & CUSB in 1985. • Massive enough to produce: • Knowledge of Bs production at Y(5S) essential for assessing the potential of Bsphysics at a high luminosity e+e- collider. • A clean source of BS decays is valuable to help interpret New Physics found directly at the LHC.

  3. Why study the Y(5S) at e+e- Colliders? • Clean source of Bs mesons • Absolute BF’s can be determined • Inclusive & Exclusive • Hadron collider only determines relative BF’s • Some decays of interest difficult for hadron machines. • Information on DG can be obtained from untagged rates or time-integrated rates to CP eigenstates (BF’s) • Modes with more than one neutral also difficult

  4. CP eigenstates Time evolution (via Schrodinger Equation) Bs Mixing Phenomenology M12 contains the off-shell, short-distance physics, ie, q=t(sensitive to new physics, dominated by top quark loop in SM) G12 from on-shell states (q=c,u) accessible to both Bs and Bs.(less sensitive to NP, bccs tree diagrams dominant)

  5. Bs Phenomenology, cont • Allowing for CPV, weak eigenstates are: • Define: • Solve Schrodinger Equation: where in SM:  In SM, Mass Eigenstates should be ~ CP eigenstates, DG=DGCP, otherwise NP • One then obtains: For B0, DG~0, and one recovers the familiar form: For B0J/yKs

  6. Bs and CKM • Bs decays provide an alternate probe from which to extract gand the Bs mixing phase. • BsJ/yf, J/yh, J/yh • Measures Bs mixing phase • J/yh, J/yh pure CP eigenstates; requires excellent photon reconstruction • J/yf requires a time-dependent angular analysis: • Fit for ratio of CP amplitudes, DGs/Gs and sin(2c). • s(DGs/Gs)~0.02 with 2 fb-1 at LHCb • BsDsK • Interference between direct tree and mixing + tree • Measures sin(g+2c) • Likely insensitive to NP. Caveat: Must be able to resolve the fast Bs oscillations for these measurements !! Oscillation length Dz ~ gctosc~26 mmfor Asymmetric B factorycompared to a z resolution of ~150 mm No TD-CPV at Y(5S) But, Dms~17 ps-1

  7. In the limit that intermediatestates are Ds(*)+Ds(*)- andall CP even, we get thefamiliar result that: Combining these two gives |cosf| DG @ Y(5S) Dunietz, Fleischer, & Nierstehep-ph/0012219 • Some measurements only require untagged time-dependent rates or time-integrated rates(BF’s) • For example, fromlifetimes of CP (GCP=1/tCP) and flavor-specific final (GFS=1/tFS)states, one finds: • Only measures product DGcosf • New physics can alter the mixing phase ffSM+fNP. • NP unlikely in DGCP, since it’s dominated by trees • One can show that using BF’s: Where wfoddis a weight reflecting the relativeamount of CP even vs CP odd in f.

  8. Status of DGs • Can use previously mentioned technique to get | cosf|, butreally need to measure BF’s DS(*)+DS(*)-, J/y h(), J/y f, etc (angular analysis for VV states to get CP even fraction). • In the presence of NP fSMfSM+fNPfNP • Measurements of DG & DGCP • DG: D0: 0.17±0.09±0.03 & CDF: (statistically limited) • DGCP:t(BsK+K-)=1.53±0.18±0.02 ps (CDF) • DGCP: B(Ds(*)+Ds(*)-)=(7.1±3.5±2.7)% • These exclusive modes could be measured by a B-factory. See A. Drutskoy [hep-ph/0604061] • If there is a new physics phase then DG=DGSM cosf; the Ds* modes difficult at LHCb because of the g from the DS* decay  B factories at Y(5S) can measure it… FPCP’06, R. Van Kootenhep-ex/0606005

  9. What do we know about the Y(5S) ?

  10. Previous Data Samples CLEO PRL 54 381, 1985 • 1985: Scans of Y(5S) region: • CLEO: 0.07 fb-1 (on peak) • CUSB: 0.12 fb-1 (on peak) Y(6S)? Y(5S) CUSB PRL 54, 377, 1985 CUSB fit to modified potential model Evidence for Bs production at Y(5S) inconclusive

  11. Recent Data Collected at the Y(5S) • 2003: CLEO collected 0.4 fb-1 on the Y(5S). Goals were: • Understand the composition of the Y(5S) • Assess the physics potential of a B-factory operating at the Y(5S) • Measurements of Bs decays. • 2005: Belle collected about 1.86 fb-1 on Y(5S) • 2006: Belle collected about 22 fb-1 on Y(5S) (being processed)

  12. Count hadronic events Subtract continuum from below-Y(4S) Scale by ratios of luminosity, s=Ecm2 Luminosity ratio significant source of systematic error, since s(5S)~0.1s(continuum), and 300 MeV below Y(5S) Cross-check L ratio using high momentum tracks (0.6<p/pmax<0.8) Results: CLEO: s(5S)=(0.301±0.002±0.039) nb BELLE: s(5S)=(0.305±0.002±0.0016) nb Remarkable agreement, DR~0.4 Cross-Section Measurements PRL95, 261801 (1995) hep-ex/0605110

  13. Separating Final States Many final states accessibleat the Y(5S) MC • Photon from B*Bg not used. • B momentum contains sufficient information for kinematic separation. • All 2-body decays are kinematically separated from one another. • The B(*)B(*)p(p) are also separatedfrom the 2-body, but not well separated from each other. • Only for BB and BsBs does Mbc = M(B), M(Bs), respectively. • Biases from neglect of 50 MeV g:B*B* : Mbc(B) = M(B*)+1.7 MeV Bs*Bs*: Mbc(Bs) = M(Bs*)+0.1 MeV

  14. Ordinary B Mesons @ Y(5S) Phys. Rev. Lett.96:152001,2006 Reconstruct B mesons in 25decay modes • BD(*)p, D(*)r • D0Kp, Kpp0, Kppp • D+  Kpp • BJ/yK+, J/yK*0,J/yKS Invariant mass (GeV) s(BBX)=(0.177±0.030±0.016) nb, s(5S)=(0.301±0.002±0.039) nb

  15. B Cross-Sections & BS* Mass Project data onto Mbc axis Fit for BB, BB*, and B*B* yieldsand <Mbc> for each. • Production largest for B*B*, consistent with models: • s(B*B*)/s(BBX) = (74±15±8)% • s(BB*)/s(B*B*) = (24±9±3)% • s(BB)/s(B*B*) < 22% @ 90% cl • BS* mass • Compute DMbc = Mbc(Bs*)-Mbc(B*) • Largest systematic, beam energy scale cancels • DM = DMbc + 1.6 MeV (kinematic bias) • Obtain • M(BS*)-M(B*)=(87.6±1.6±0.2) MeV • Use precise B* mass to get M(Bs*) • M(Bs*)=(5411.7 ± 1.6 ± 0.6) MeV • M(BS*)-M(BS)=(45.7±1.7±0.7) MeV • Consistent, as expected from Heavy Quark Symmetry with M(B*)-M(B) =45.78±0.35 MeV CLEO B*B* BBpp BB* BB(*)p BB B*B* peak gives the beam energycalibration ! 6.4±1.3 MeV from expected!

  16. Exclusive Bs Analyses (CLEO) Phys. Rev. Lett.96:022002,2006 4 cand. 10 cand.

  17. Exclusive Bs Analyses (Belle) Bs J/y f/h Bs Ds+p- Ds+  f p+ , Ds+ K*0 K+, Ds+ Ks K+ h  gg 9 events in Bs* Bs* 3 events in Bs* Bs* Bs Ds(*)+r- Bs Ds*+p- 4 events in Bs* Bs* 7 events in Bs* Bs*

  18. 5.408< MBC<5.429 GeV/c2 5.36< MBC<5.38GeV/c2 5.384< MBC<5.405GeV/c2 Bs* Bs* Bs* Bs Bs Bs Nev=20.0 ± 4.8 6.7 s Fits for BsBs, BsBs*, Bs*Bs* (Belle) Take slices in Mbc Project on DE (all modes combined) Potential models predict Bs* Bs* dominance over Bs*Bs and BsBs channels, but not so strong.

  19. Use inclusive particle yield Choose a particle that has very different decay rates from B & BS Ex: DS measure Inclusive Bs Analyses measure Model estimate based on quark level diagrams and measured ordinary B decay rates  B(BS→DS X) =(92±11)% Solve for fs

  20. fs from Ds Yields (CLEO) Y(5S) Y(4S) continuum Y(4S) Branching Fraction Y(5S) Dsfp x ( |p|/Ebeam ) B (BS→DS X) =(92±11)%

  21. fs from Ds Yields (Belle) Drutskoy, et alhep-ex/0608015 Dsfp+ Y(5S) After continuum subtraction and efficiency correction: B (Dsfp+) = (4.4 ± 0.6)% from PDG 2006 B(Y(5S) -> DsX) / 2 = (23.6 ± 1.2 ± 3.6) % fs = (17.9 ± 1.4 ± 4.1 )% 3775 ± 100 ev Nbb and BF(Dsfp)dominant uncertainties points:5S hist: cont

  22. fs from D0 Yields (Belle) B(Bs D0X) = (8 ± 7) % points:5S hist: cont Y(5S) Spectator model, ala hep- ex/0508047 CLEO PDG 2006: B(B -> D0X) = (64.0 ± 3.0) % D0 -> K-p+ B(D0 K-p+) = (3.80 ± 0.07) % (55009 ± 510) ev After continuum subtraction and efficiency correction: Bf (Y(5S)  D0X) / 2 = (53.8 ± 2.0 ± 3.4) % Nbbdominant uncertaintiy fs = (18.1 ± 3.6 ± 7.5 )% Combining with Ds result: fs = (18.0 ± 1.3 ± 3.2 )%

  23. Measurement of fSUsing f Yields known • Here we need B(BS→fX) • Use CLEO-c inclusive yield measurements: B(Do→fX)=(1.0±0.10±0.10)% B(D+→fX)=(1.0±0.10±0.20)% B(DS→fX)=(16.1±1.2±1.1)% (Preliminary [hep-ph/0605134 ], DsfX updated) • From B(B →fX) = (3.5±0.3)% find most of f’s arise from B→D→f & B→DS→f • Predict that B(BS→fX) = (16.1 ± 2.4)%

  24. Reconstruct fK+K- CLEO inclusive f yields, for x<0.5, R2<0.25 Y(5S) Y(4S), scaled Results on fSUsing f Yields Continuum-subtracted spectra On Y(4S) On Y(5S) Cont’m

  25. Summary of fSMeasurements • Plot shows statistical (dark line) & systematic errors added linearly • Recall, model dependencies • A model-independent approach, exploiting the large difference in mixing between B and Bs and measuring like-sign and opposite sign leptons.(Sia & Stone, hep-ph/0604021) • Could also do a double-taggedanalysis, ala Mark III, CLEO-c. (Both require large samples)

  26. Rare Exclusive Bs decays (Belle) Access toDG/G gg fg K+K- DS(*)+DS(*)-

  27. Expected Yields at Y(5S) ~100K Bs produced per fb-1 at Y(5S). O(10%) model-independent Bs BF’s would probably require several ab-1 at Y(5S)(my back of the envelope)

  28. Summary • More recent investigations of Y(5S): • About 1/3 of Y(5S) produces Bs pairs, mostly Bs*Bs*. • Ordinary B production dominated by B*B* (~2/3 of all B production) • Both consistent with coupled-channel model predictions, although Bs*Bs* rate appears higher than predictions (20 fb-1 sample from Belle should resolve this). • Precise Bs* mass obtained from CLEO. • Large mixing frequency makes time-dependent CPV measurements inaccessible at Y(5S). This is where LHCb excels. • Y(5S) data can provide some complementary information on DG to the time-dependent and time-integrated measurements at LHCb. • Results from ~20 fb-1 Y(5S) sample from Belle should be available early in 2007, stay tuned…

  29. Backups

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