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A. Drutskoy, University of Cincinnati

Results and prospects of Y(5S) running at Belle. A. Drutskoy, University of Cincinnati. LPHE seminar. March 14, 2008, Lausanne, Switzerland. LPHE seminar Results and prospects of Y(5S) at Belle , March 14, 2008 , Lausanne A. Drutskoy. Outline. 2.

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A. Drutskoy, University of Cincinnati

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  1. Results and prospects of Y(5S) running at Belle. A. Drutskoy, University of Cincinnati LPHE seminar March 14, 2008, Lausanne, Switzerland. LPHE seminarResults and prospects of Y(5S) at Belle, March 14, 2008 , Lausanne A. Drutskoy

  2. Outline 2 Introduction. Recent Belle measurements at Y(5S). Prospects of Bs meson (and other) studies at Y(5S). My thoughts (speculations) about Y(5S) -> Y(6S) ->… . Conclusion.

  3. CLEO PRL 54, 381 (1985) (5S) e+ e-hadronic cross section 3 - - - - - + (cc,ss,uu,dd) bb (4S) e+ B _ B e- (6S) Resonance to continuum hadron production ratios are Y(4S)/Cont ~ 1./3.5 and Y(5S)/Cont ~ 1./10.

  4. CLEO PRL 54, 381 (1985) CLEO PRL 54, 381 (1985) (5S) (5S) Running at Y(4S) and Y(5S) 4 (4S) Asymmetric energy e+e- colliders (B Factories) running at Y(4S) : Belle and BaBar 1985: CESR (CLEO,CUSB) ~ 0.1 pb-1 at Y(5S) 2003: CESR (CLEO III) ~ 0.42 fb-1 at Y(5S) 2005: Belle, KEKB ~ 1.86 fb-1 at Y(5S) 2006, June 9-31:Belle, KEKB ~21.7fb-1 at Y(5S) _ e+ e- ->Y(4S) -> BB, whereBisB+orB0meson _ _ _ _ _ _ _ _ e+ e- -> Y(5S) -> BB,B*B, B*B*, BBp, BBpp, BsBs, Bs*Bs, Bs*Bs* where B* -> B gandBs* -> Bsg G(Y(5S)) = 110  13MeV/c2 (PDG) M(Y(5S)) = 10865  8 MeV/c2 (PDG) Bs rate is ~10-20% => high lumi e+e-collider at Y(5S) -> Bs factory.

  5. 5 First Y(5S) runs at the KEKB e+e-collider Belle Electron and positron beam energies were increased by 2.7% (same Lorentz boost bg = 0.425) to move from Y(4S) to Y(5S). 8 GeVe- 3.5 GeV e+ No modifications are required for Belle detector, trigger system or software to move from Y(4S) to Y(5S). Integrated luminosity of ~1.86 fb-1 at 2005 and ~21.6 fb-1 at 2006 was taken by Belle detector at Y(5S). The same luminosity per day was taken at Y(5S) as it is at Y(4S). Very smooth running

  6. New 2006 runs at Y(5S) at Belle 6 Belle collected data at Y(5S): June 9-June 31, 2006 =>21.7fb-1 Exceeded 1.2fb-1/day for the first time at Y(4S). Daily luminosity Correction factor(1.056) is necessary for 5S run due to smaller Bhabha Cross section. 5S run ~22 fb-1 Off-resonance run

  7. Integrated luminosity 7 Belle (10 Mar 08) All: ~778 fb-1 , Cont: ~68 fb-1 , Y(5S): ~24 fb-1 Belle + BaBar > 1 ab-1

  8. CLEO PRL 54, 381 (1985) (5S) Hadronic event classification 8 hadronic events at U(5S) u,d,s,c continuum U(5S) events b continuum N(bb events) = N(hadr, 5S) - N(udsc, 5S) bb events B0, B+ events Bs events fs = N(Bs(*) Bs(*)) / N(bb) Bs* Bs* channel Bs* Bs Bs Bs

  9. Number of bb events, number of Bs events 9 - - - - Continuum event yield (uu,dd,ss,cc) is estimated using data taken below the Y(4S): Ncont(5S) = Ncont(E=10.519)* L(5S) / L(cont) * (Econt/E5S)2 (e5S/ econt) Y(5S) : Lumi = 1.857 ± 0.001 (stat) fb-1 Cont (below 4S) : 3.670 ± 0.001 (stat) fb-1 Nbb(5S) = 561,000 ± 3,000 ±29,000 events => 5% uncertainty from luminosity ratio CLEO: Nbb(5S)/ fb-1 = 310,000 ± 52,000 Nbb(5S) / fb-1 = 302,000 ±15,000 How to determine fs =N(Bs(*) Bs(*)) / N(bb)? bb at Y(5S) _ _ Bs Bs B B Bf (Y(5S) -> Ds X) / 2 = fsBf (Bs -> Ds X) + (1-fs) Bf (B -> Ds X) x x 1. Bf (Bs -> Ds X) can be predicted theoretically, tree diagrams, large. 2. Bf (B -> Ds X) is well measured at the Y(4S).

  10. Inclusive analyses: Y(5S)->Ds X, Y(5S)->D0X 10 points:5S hist: cont points:5S hist: cont Y(5S) P/Pmax<0.5 Ds-> fp+ Ds-> fp+ 3775 ± 100 ev D0 -> K-p+ After continuum subtraction and efficiency correction: Bf (Y(5S) -> Ds X) 2 = (23.6 ± 1.2 ± 3.6) % L = 1.86 fb-1 Nbb(5S) = Bf (Y(5S) -> D0 X) 2 = (53.8 ± 2.0 ± 3.4) % 561,000 ± 3,000 ±29,000 events fs = N(Bs(*) Bs(*)) / N(bb) => = (18.0 ± 1.3 ± 3.2 )% s(Y(5S)->bb) = (0.302 ± 0.015)nbat E=10869MeV

  11. Signature of fully reconstructed exclusive Bs decays 11 BsBs , Bs*Bs, Bs*Bs* MC Zoom Mbc vs DE Mbc vs DE whereBs* -> Bsg e+ e- -> Y(5S) -> BsBs, Bs*Bs,Bs*Bs*, Reconstruction: Bsenergy and momentum, photonfrom Bs* is not reconstructed. Mbc = E*beam2 – P*B2 , DE = E*B – E*beam Two variables calculated: Figures (MC simulation) are shown for the decay mode Bs -> Ds-p+ with Ds- -> fp- . The signals for BsBs, Bs*Bs and Bs* Bs* can be separated well.

  12. Exclusive Bs -> Ds(*)+p-/r-and Bs-> J/y f/hdecays 12 Data at Y(5S), 1.86 fb-1 Bs -> Ds+p- Bs -> J/y f/h Bs -> Ds*+p- Bs -> Ds(*)+r- 9 evnts in Bs* Bs* 4 evnts in Bs* Bs* 7 evnts in Bs* Bs* 3 evnts in Bs* Bs* N(Bs*Bs*) / N(Bs(*)Bs(*))= (93± 79 ±1)% 5.408<MBC<5.429GeV/c2 Potential models predict Bs* Bs* dominance over Bs*Bs and BsBs channels, but not so strong. Bs* Bs* Nev=20.3 ± 4.8 Conclusions: 1. Belle can take ~30 fb-1 per month. 2. Number of produced Bs at Y(5S) is ~105/fb-1. 3. Bs*Bs* channel dominates over all Bs(*)Bs(*). 4. Backgrnds in exclusive modes are not large.

  13. Number of Bs in dataset 13 hadronic events at Y(5S) bb continuum included Lumi = 1.857 fb-1 bb events N ev =561,000 ± 3,000 ±29,000 fs = (18.0 ± 1.3 ± 3.2 )% Bs events N ev =101,000 ± 7,000 ±19,000 f(Bs*Bs*) = (93 ± 79 ± 1)% Bs* Bs* channel N ev =94,000 ± 7,000 ±20,000 ~105 Bsmesons per 1fb-1 at Y(5S) Biggest uncertainty comes from fssystematics. How to improve it (3 times)?

  14. Improved measurement of fs 14 How to measure fs with 5% uncertainty ? I spent a lot of time thinking about that. It could be: 1. CLEO method, from Bf(Y(5S)-> Ds X), with better statistics. 2. Using same-sign lepton-lepton sample, maybe with z-distance measurement between profile-lepton vertices 3. J/y vertex xy-distance from profile. 4. Bf(B-> D+p-), Bf(B-> D0p-), Bf(B-> D*0p-) measurements. 5. Number of slow photons from Bs* decays. No one of these methods is perfect

  15. New Belle results with 23.6 fb-1 15 First observation ofBs-> fg and new upper limit forBs-> gg. Bf (Bs->fg)=(5.7 +1.8+1.2) 10-5 -1.5-1.1 Jean Wicht Bf (Bs->gg) < 8.7x10-6(90% CL) First measurement ofY(5S) -> Y(nS) p+p-decays (21.7 fb-1).

  16. Is the ϒ(10860) purely ϒ(5S)? 16 -> look for: m+m-h+h- U(2S) e+e- -> U(1S) p+p-X e+e- -> U(2S) p+p-X U(3S) U(2S) arXiv:0710.2577[hep-ex] (accepted PRL) U(1S) Study motivated by observation of Y(4230) -> J/Yp+p- signal (analogous?). U(1S)

  17. Expectation: Υ(5S) width comparable to Υ(2S/3S/4S) larger by > 102 Is the ϒ(10860) purely ϒ(5S)? 17 Y(5S) -> U(nS) h+h- 4 modes seen : Conclusion: not pure Υ(5S)? Energy scan: 12/07 .

  18. New Belle results with 23.6 fb-1 18 First observation ofBs-> fg and new upper limit forBs-> gg. Bf (Bs->fg)=(5.7 +1.8+1.2) 10-5 -1.5-1.1 Jean Wicht Bf (Bs->gg) < 8.7x10-6(90% CL) First measurement ofY(5S) -> Y(nS) p+p-decays (21.7 fb-1). First measurement ofBs-> X +l-ndecay.

  19. Motivation, feasibility of Bslifetime measurement. 19 PDG 2007:Bf( B0->X+l-n ) = ( 10.33  0.28 )% Semileptonic decays have no hadronic corrections. Theory predicts about 12%. It is not yet understood by theory. Some recent models predict better (dis)agreement. Calculation problems? Exotics? Maybe semilep. Bs decays can shed some light. t(B0) > t(Bs) - 2.9sdifference (in contrast with theory). Bs and Ds lifetimes can be measured using Ds vertex, lepton track and beam profile. K+ K- p+ m+ Ds+ This analysis requires much more work … . z

  20. First measurement of Bs-> X+l -n decay 20 Electron Muon DATA DATA MC 23.6 fb-1 23.6 fb-1 from Ds,D… from Bs Electron : Bf( Bs->X+e-n ) = ( 10.9  1.0  0.9 )% Muon : Bf( Bs->X+m-n ) = ( 9.2  1.0  0.8 )% preliminary preliminary Combined fit (electron+muon) : Bf( Bs->X+l-n ) = ( 10.2  0.8  0.9 )% Assuming similar decay widths and t(Bs)/t(B0)=1.000.01 (theory; exp.diff.~2.3s) it can be compared to PDG 2007:Bf( B0->X+l-n ) = ( 10.33  0.28 )%

  21. New Belle results with 23.6 fb-1 21 First observation ofBs-> fg and new upper limit forBs-> gg. Bf (Bs->fg)=(5.7 +1.8+1.2) 10-5 -1.5-1.1 Jean Wicht Bf (Bs->gg) < 8.7x10-6(90% CL) First measurement ofY(5S) -> Y(nS) p+p-decays (21.7 fb-1). First measurement ofBs-> X +l-ndecay. Measurement ofBs-> Ds+p-andBs->Ds+K-decays. R. Louvot, T. Aushev, J.Wicht Bf (Bs->Ds+p-)=(3.31 +0.31+0.67) 10-3 -0.30-0.64 Bf (Bs->Ds+p-)=(2.2 +1.1+0.5) 10-4 R=0.066 0.015 -0.9-0.4

  22. Why it is interesting? 22 Bf (Bs->Ds+p-)=(3.31 +0.31+0.67) 10-3 1. -0.30-0.64 Bf (B->D+p-)=(2.68  0.13) 10-3 PDG: W-exchange diagram? Difference is not yet significant. 2. M(Bs*)=5417.4  0.4  1.0 MeV/c2 PDG: M(Bs)=5366.1  0.6 MeV/c2 D(Bs0)= 51.3  1.2 MeV/c2 D(B0)= 45.78  0.35 MeV/c2 Very unexpected difference N(Bs*Bs*) / N(Bs(*)Bs(*))= (90± 3.73.9 ± 0.2)% very unexpected 3. 4. Flat B direction angular distribution –> has to be explained.

  23. Belle results expected soon with 23.6 fb-1 23 1. K. Sayeed, A. Schwartz: Bs-> J/yf and Bs->J/y Ks decays. Important for future CP studies. 2. J.-H. Chen : Search for Bs-> K+ K- decay. CP eigenstate, can be used in future for DGs/Gs measurement. Analysis started: 1. S.Esen : Measurement Bs->Ds+(*)Ds-(*) Mostly CP eigenstates, important for indirect DGs/Gs measurement.

  24. DGs/Gsmeasurement fromBf (Bs -> Ds+(*) Ds-(*)) 24 MBs = (MH + ML)/ 2 Gs = (GH + GL)/ 2 Dms = MH – MLDG = GL- GH>0 in SM ( ) ( ) d Bs Bs “ i - Schrodinger equation i = ( M – / 2 G ) d t Bs Bs Matrices M and G are t-dependent, Hermitian 2x2 matrices Assuming CPT: M11 = M22G11 = G22 | BH,L(t) > = exp( - ( iMH,L+GH,L/ 2)t ) | BH,L> SM: bs=arg(-Vts Vtb*/ Vcs/ Vcb*) =O(l2) - no CP-violation in mixing BSM : fs = arg (- M12/ G12) 2qs = fsDGs = 2 | G12| cos 2qs

  25. DGs/Gsmeasurement fromBf (Bs -> Ds+(*) Ds-(*)) 25 (first proposed by Y. Grossman) DGs = 2 | G12| cos fs DGsSM = DGCPs = 2 | G12| Since DGCPsis unaffected by NP, NP effects will decreaseDGs. DGCPs = S G(CP=+) – SG(CP= –) Bs->Ds(*) + Ds(*) - decays have CP-even final states with largestBF’s of ~ (1-3)% each, saturatingDGs/Gs . DGCPs Bf(Bs->Ds(*) + Ds(*) - ) ~ ~ Gs 1- Bf(Bs->Ds(*) + Ds(*) - ) / 2 To prove this formula experimentally : a) Contribution of Bs -> Ds+(*) Ds-(*) np is small b) Most of Bs -> Ds+ Ds- * and Bs -> Ds+* Ds- * states are CP- even. Assuming corrections are small (~5-7%), Bfmeasurement will provide information aboutDGCPsor |G12|.

  26. DGs/Gs measurement from Bf (Bs -> Ds+(*) Ds-(*)) 26 Expected with 25 fb-1 at Y(5S): Y(5S), 1.86 fb-1 N ~ 107 x 2x10-4 x 10-2~ 5 ev Eff(Bs->Ds+ Ds-) ~ 2x10-4 N ~ 107 x 10-4 x 2x10-2~ 5+5 ev Eff(Bs->Ds*+ Ds-) ~1x10-4 N ~ 107 x 5x10-5 x 3x10-2~ 4 ev Bs-> Ds+ Ds- Eff(Bs->Ds*+ Ds*-) ~5x10-5 Bs-> Ds*+ Ds- Bs-> Ds*+ Ds*- =>Accuracy ofBf (Bs->Ds(*)+Ds(*)-) has to be ~25%. Ds+ -> fp+ , K*0 K+, Ks K+ DGCPs Bf(Bs->Ds(*) + Ds(*) - ) should be compared with direct DGs/Gsmeasurement to test SM. ~ <= ~ Gs 1- Bf(Bs->Ds(*) + Ds(*) - ) / 2 DGs/Gslifetime difference can be measured directly with high accuracy at Y(5S) and also at Tevatron and LHC experiments.

  27. Further physics program with 23 fb-1 27 1. Bs -> Ds+r- , Bs -> Ds+ a1-, Bs -> Ds*+p- ,Bs -> Ds*+r- , Bs -> Ds*+ a1-. BF’s should be compared with B0 partners to test SU(3). 2. Bs -> J/y h,J/yh’ , J/yw, J/y f0(980) , … ,Bs-> J/y K+ K-. What is fraction of ss component in different mesons? Quark model : y(h)=(uu+dd-ss)/ 3 y(h’)=(uu+dd+2ss)/ 6 B(Bs0->J/yh) = 1/3 B(Bs0->J/yf) B(Bs0->J/yh’) = 2/3 B(Bs0->J/yf) Mixed channels? Enhanced branching fractions?

  28. Further physics program with 23 fb-1 28 3. Bs -> DsJ+p- (4 states). Interesting physics issues, critical test of DsJ nature. Inclusive DsJ production study? 4. Bs -> D0 K0(*). Statistically significant signals are expected with BF’s predicted at [C-K.Chua,W-S.Hou, hep-ph/0712.1882]. Color-suppressed Bf(Bs->D0K0) ~8x10- 4 => ~20 signal events should be seenwith 23.6fb-1 at Y(5S).

  29. Color-suppressed Bs-> D0 K0decay 29 Color-suppressed Color-suppressed FSI Bf (B0->D0p0) (2.91 ± 0.28) x10- 4 ~ 0.1 = ~ Bf (B0->D+p-) (3.4 ± 0.9) x10- 3 Which diagram, color-suppressed or FSI, is dominant in B0->D0p0 decay ? Decay mode Bs->D0K(*)0hasno FSI diagram. If the ratio Bf(Bs->D0K0)/Bf(Bs->Ds+p-) ~0.1, then color-suppressed diagram dominates. If the ratio is significantly smaller, then FSI diagram dominates.

  30. Further physics program with 23 fb-1 30 5. Bs -> Ds+ l-n,Bs -> Ds*+ l-n (Bs->K+ l-n?). Important SU(3) test. CDF obtained large DsJ semileptonic BF (?). 6. Bsdecays with baryons (with L0 baryons). Largest B0 baryonic Bf’s are ~10-3. Is it similar in Bs decays? 7. Bslifetime measurement. Different samples can be used: fully reconstructed events, CP-fixed modes, two lepton events, Ds+ lep+ events … . Good accuracy is expected (5-10%). Important measurement.

  31. Feasibility of Bslifetime measurement with same-sign leptons 31 Lifetime can be measured using two fast same sign lepton tracks and beam profile. To remove secondary D meson semileptonic decays: P(l)>1.4 GeV. Y(5S) : Bs(l +) Bs(l +) / Bs(l +) Bs(l -) = 100% Y(4S) : B(l +) B(l +) / B(l +) B(l -) ~ 10% m+ m+ Beam profile Dz = bgc Dt Bs Y(5S) Bs Z beam ~ 3 mm; Dz ~ 0.1- 0.2 mm.

  32. 32 Comparison with Fermilab Bs studies. There are several topics, where Y(5) running has advantages comparing with CDF and D0: 1) Model independent branching fraction measurements. 2) Measurement of decay modes withg, p0andhin final state (Ds+r-). 3) No trigger problems formultiparticlefinal states (likeDs+ Ds-). 4) Inclusive branching fraction measurements (semileptonic Bs). 5) Partial reconstruction ( Bf (Ds+ l-n)using “missing- mass” method). There are also disadvantages: 1) We have to choose between running at Y(4S) or Y(5S). 2) Number of Bs is smaller than in Fermilab experiments. 3) Vertex resolution is not good enough to measure Bs mixing (???).

  33. Future physics program at Y(5S) 33 Realistic value of 200 fb-1 Optimistic value of 2000 fb-1 Only big deals: 1. DGs/Gsmeasurement Decay modes Ds(*)Ds(*), K+K-, ff, fg, J/yh(f) ~500 CP-fixed events with 200fb-1 => 5-10% accuracy in Gs. Measurement ofBs-> ggdecay 2. It also requires about 1000fb-1 to measure. 3. Bs mixingmeasurement

  34. Bs mixing measurement 34 It is often postulated, that Bs mixing cannot me measured at the Y(5S). Have anybody checked it? Is it correct or not? Can we measure Bs mixing? Let’s check it. Distance between max and min of oscillation function: Dz= pDmsbgc = 22.5mm with bg=0.425 Can we increase bg at Y(5S) runs by 50%? Probably yes. Then we need to get single vertex resolution of ~20 mm. Is is planned resolution for fast (00 dip angle) tracks (next slide). => with high statistics we can select high vertex resolution events. Yes, we can.

  35. T.Kawasaki, Atami BNM2008 Jan 2008 Impact Parameter resolution Calculated by TRACKERR r-fdirection z direction [cm] [cm] 0.02 0.03 LoI ‘04 sBelle SVD2(now) For p- 0.2GeV 0.5GeV 1.0GeV 2.0GeV 0.01 20mm 0 1.4 sinq Occupancy effects. Degradation of intrinsic resolution is included. Efficiency loss is NOT included Beampipe radius is important Competitive performance as the current SVD

  36. CLEO PRL 54, 381 (1985) (5S) What else can be done at Super B Factory? 36 PDG (Z->bb, pp at S1/2=1.8TeV) b hadron fraction(%) B+ , B0 39.8 ± 1.0 Bs 10.4 ± 1.4 b baryons 9.9 ± 1.7 Rates at e+e- continuum should be similar, baryon production is large. M(Lb)= (5624 ± 9) MeV/c2 M(Lb)x2 = (11248 ± 18) MeV/c2 => 6.3 % up from Y(4S) CME. Can Super B factory CM energy range be increased ? M(Bc)= (6286 ± 5) MeV/c2 _ _ _ _ e+e- Y(6S,7S) BsBs, LbLb, BcBc, Xb Xb … ?

  37. Conclusions 37 Bs decays with branching fractions down to 10-6 can be measured with statistics of ~100 fb-1 at e+e- colliders running at Y(5S). Many important SM tests can be done with statistics of the order of 1000 fb-1. Bs studiesat e+ e- colliders running atY(5S) have some advantages comparing with hadron-hadron colliders. These colliders are in some sense complementary. It is important to have more flexibility in beam energies.

  38. Background slides

  39. Belle Detector Cherenkov detector n=1.015~1.030 SC solenoid 1.5T 3.5GeV e+ EM calorimeter (CsI(Tl)) TOF counter 8GeV e- Central drift chamber He(50%)+C2H6(50%) m / KL detector Si vertex detector

  40. dz resolution T.Kawasaki, Atami BNM2008 Jan 2008 dz dz resolutoin SuperB SVD3mod SVD3 For p 0.2GeV 0.5GeV 1.0GeV 2.0GeV

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