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Charm Physics - Experimental

Charm Physics - Experimental. Sheldon Stone, Syracuse University. y  D o D o , D o  K - p +. K +. “I charm you, by my once-commended beauty” Julius Cæsar, Act II, Scene I. K -. p +. p -. K +. K -. Why Study Charm? – Overview.

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Charm Physics - Experimental

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  1. Charm Physics - Experimental Sheldon Stone, Syracuse University yDoDo, DoK-p+ K+ “I charm you, by my once-commended beauty” Julius Cæsar, Act II, Scene I K- p+ p- K+ K- FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  2. Why Study Charm? – Overview • Tests of Theoretical Models necessary to interpret critical CKM data, usually obtained from B decays • CKM Matrix elements: Charm decays can be used to determine directly Vcd & Vcs, indirectly Vub and contribute to Vcb • Engineering measurements: e. g. absolute B's (& some inclusive ones, i.e. Do,+f X) • New Physics: May see in charm directly • SM CPV suppressed, perhaps also rare decays & mixing FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  3. Use of Charm data to improve B measurements, etc.. Some examples:

  4. Artists view of current constraints ±1s bands, not precise h r • Idea is that (h,r) can be determined in several ways, differences will indicate new physics Item: Bs mixing • To relate constraints on CKM matrix in terms of say r & h need to use theoretical estimates of fBs2BBs/ fBd2BBd • CLEO-c’s job: Measure fDs/fD+ to check theoretical lattice calculations, best unquenched lattice. FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  5. In general for all pseudoscalars: Calculate, or measure if VQq is known Leptonic Decays: D +n Introduction: Pseudoscalar decay constants: c and q can annihilate, probability is  to wave function overlap Example : _ FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  6. p • B-factories (e+e-) + fixed target & collider experiments at hadron machines • D displaced vertex • D*+ p+D0 tag K (ps) D0 e+ e- Experimental methods • DD production at threshold: used by Mark III, and more recently by CLEO-c and BES-II. • Unique event properties • Only DD not DDx produced • Large cross sections: s(DoDo) = 3.720.09 nbs(D+D-) = 2.820.09 nb • Ease of B measurements using "double tags“ • BA = # of A/# of D's World Ave Continuum ~14.5 nb FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  7. D+K-p+p+ at the y´´ (CLEO-c) Single tags Double Tags D+K-p+p+ & D-K+p-p- 377 events D+K-p+p+ or D-K+p-p-, 15,120 events 57 pb-1 of data at y(3770), CLEO now has 281 pb-1 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  8. B(DoK-p+) Three best measurements B (%) Error(%) Source 3.820.070.12 3.6 CLEO II 3.900.090.12 3.8 ALEPH 3.910.08 0.09 3.1 CLEO-c Absolute B Results B(D+K-p+p+) Three best measurements B (%) Error(%) Source 9.30.60.8 10.8 CLEO II 9.11.30.4 14.9 MK III 9.52 0.250.27 3.9 CLEO-c CLEO-c (not in average) FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  9. Leptonics & Semileptonics at CLEO-c • Ease of leptonic & semileptonic decays using double tags & MM2 technique We know ED=Ebeam, pD = - pD • Search for peak near MM2=0 • Since resolution ~ Mpo, reject extra particles with calorimeter & tracking • Note that this method can be used to evaluate systematic errors on e, simply by using double tags with one missing track • Sometimes people use Umiss = Emiss -|Pmiss|   2 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  10. Technique for D+m+n • Fully reconstruct one D • Seek events with only one additional charged track and no additional photons > 250 MeV to veto D+p+po • Charged track must deposit only minimum ionization in calorimeter • Compute MM2: If close to zero then almost certainly we have a m+n decay ± FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  11. Single Tag Sample • From 281 pb-1 K-p+ p+ p0 K-p+ p+ Ksp+ Ksp+p+ p- K-K+ p+ Ksp+p0 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  12. Data have 50 signal events in 281 pb-1 Measurement of fD+ MC Expectations from 1.7 fb-1, 6X this sample FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  13. Deriving a Value for fD+ • Tags are 158,354 events • B(D+m+n)=(4.40±0.66+0.09)x10-4 • fD+ = (222.6±16.7+2.3) MeV • B(D+e+n) <2.4x10-5 @ 90% c.l. Efficiencies: m+ detection (69.4%); extra shower (96.1%); correction for easier tag reconstruction in m+n events (1.5%) -0.12 -3.4 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  14. Comparison to Theory • BES measurement based on 2.67±1.74 events • Current Lattice measurement (unquenched light flavors) is consistent • But systematic errors on theory & statistical errors on data are still large 201±3±17 MeV FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  15. Inclusive semileptonic branching fractions CLEO-c 281 pb-1 • Tagged sample: only “golden modes” D0K-p+ and D+K-p+ p+ • Identify e, p, K right-sign and wrong-sign samples, use unfolding matrixtrue e population. • Correction for pe- cut dG/dp(ps-1GeV-1) e- preliminary Lab momentum spectrum – no FSR correction FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  16. Exclusive Semileptonic Decays • Best way to determine magnitudes of CKM elements, in principle is to use semileptonic decays. Decay rate |VQiQf|2 • This is how Vus (l) and Vcb (A) have been determined VQiQf • Kinematics: • Matrix element in terms of form-factors (for DPseudoscalar l+n • For l = e, contribution of f-(q2)0 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  17. (~420 events) (~1300 events) B= (3.44±0.10±0.10)% Events / ( 10 MeV ) U = Emiss– |Pmiss| (GeV) U = Emiss– |Pmiss| (GeV) B= (5.70±0.28±0.25)% Cabibbo Favored Semileptonic Decays These are the dominant modes, so backgrounds are almost non-existent FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  18. (110 events) (30 events) Events / ( 10 MeV ) U = Emiss– |Pmiss| (GeV) U = Emiss– |Pmiss| (GeV) 1st Observation. (30 events) (65 events) Events / ( 10 MeV ) U = Emiss– |Pmiss| (GeV) U = Emiss– |Pmiss| (GeV) Cabibbo Suppressed Semileptonic Decays FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  19. Summary of Semileptonic Branching Ratio Results Ratio to PDG • Using unquenched lattice (hep-ph/0408306) find • Vcs = 0.956±0.036±0.093±0.017 • Vcd = 0.213±0.008±0.020±0.008 stat sys exp lat lat CLEO-c new new Vcs (LEP) = 0.976±0.014 Vcd(nN) = 0.224±0.012 Currently this checks Lattice calculations FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  20. Combining Semileptonics & Leptonics • Decay rate: • Test of models in D decays: predictions of shapes of form factors (for DVector l+n there are 3 form-factors) • Note that the ratio below depends only on QCD: FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  21. Lattice comparison: fD and semileptonic ff • We can use a quantity independent of Vcd to do a CKM independent lattice check: • I obtain: • Theory and data consistent at 30% C.L. FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  22. DoKln FOCUS DATA Lattice QCD/ Fermilab MILC( 1s/2s stat.err. only) Lattice comparison – the shape of f+(q2) • Modern parameterization of the form factors proposed by Becirevic & Kaidalov (BK): Representing contributions beyond the lowest lying resonances (D*) Another model by Fajfer and Kamenik shows that including the next radial excitation in ff gives good fits to measured branching fractions. Fajfer et al. hep-ph/0506051 and 0412140 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  23. Form Factor shapes +0.03 –0.07 +0.20 –0.31 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  24. D+K-p+e+n Form Factors • K-p+ mostly K* with some s-wave (1st seen by FOCUS) • For DV e+n, use 3 helicity amplitudes Ho(q2), H+(q2), & H-(q2) • Add ho(q2)•Ho(q2) to account for s-wave term • Use 281 pb-1 Use 2447 events FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  25. H+(q2) H-(q2) ho(q2) Ho(q2) Ho(q2) Form Factor Results • Significant s-wave amplitude confirmed • Parameter-ization not great • No evidence for d or f wave FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  26. |Vub| • This important part of b physics is and will continue to be dominated by theoretical errors in the LHC era • New methods can lead to more precise results • Theory • Heavy Quark Symmetry predicts that form-factor for a Vub decay, say Bpln is the same as for Dpln at the same invariant 4 velocity, modulo corrections • Double Ratios: Grinstein, [hep-ph/9308226] FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  27. See Grinstein & Pirjol [hep-ph/0404250] Vub Theory • Thus • Specifically for Vector modes: FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  28. B±DoK± decays, Do Ksp+p- • Use Daltiz plot analysis to find gsee A. Giri et al., [hep-ph/0303187] • For the B- decay: A(B-DoK-)AB A(B-DoK-)ABrBei(dB-g) • For the Do decay: AD(s12,s13) A12,13eid12,13 A(Do KS(p1)p-(p2)p+(p3)) =A(Do KS(p1)p+(p2)p-(p3)), where sij=(pi+pj)2 (the mass) • Similar relations for B+ FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  29. Dalitz Plot Sensitivity sensitivity d2 ln L/d2 Belle Sees Clear difference FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  30. Do Ksp+p- Dalitz Analysis • Partition Dalitz plot i i • For the k bins, each denoted by i, form 4k equations: with variables ci, si, rB, dB, g FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  31. CLEO-c Can Measure ci • Measure Dalitz plot opposite a CP eigenstate tag such as K+K- or Ksf. • Supplies k of 2k+3 unknowns • Accuracy will depend on statistics • Other d’s will also be measured, such as K-p+ and K*±K± CLEO-c 281 pb-1 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  32. Searches for New Physics in Charm Decays

  33. SM |x| SM |y| BSM |x| Do-Do Mixing • Mixing could proceed via • the presence of d-type quarks in the loop makes the SM expectations for Do- Do mixing small compared with systems involving u-type quarks in the box diagram because these loops include 1 dominant super-heavy quark(t):Ko (50%), Bo (20%) & Bs (50%) • New physics in loops implies x DM/G>> y DG /2G; but long range effects complicate predictions { } Do Do From H. Nelson FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  34. Do-Do mixing: the data • The study of Do wrong-sign Kp yields has been a key step in our experimental study of Do Do mixing. • Caveats: • Complicated by interference between DCSD & mixing [strong phase d data constrain only x & y] • Complicated by CP violation Most general fit FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  35. Do Do mixing: the data II • Do semileptonic decays: Rws = ½(x2+y2) [no strong phased] • Dalitz plot analysis of D0 K p+p-(CLEO II.V) comparable sensitivity 0 s FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  36. CP/T Violation • Unexpectedly large CP violation asymmetries may be a better signature for new physics (0.01-0.001) • CP violation can be studied in a variety of ways: • Direct CP violation • CP violation in mixing • T violation in 4-body decays of D0/D+ (assuming CPT) and studying triple product correlations • Exploiting quantum coherence of DD produced in y(3770) decays FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  37. CP/T Violation: some recent data +9 -7 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  38. Future • Immediate: Take data on Ds • CLEO runs until sometime in 2008. Most of the running is now planned to be on y & y(4160) for Ds, with some ony • Errors will depend on how much data CLEO-c gets on charm • Beijing has started building a two-ring machine for this physics with much more projected luminosity FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  39. BEPCII/BESIII Project • Design • Two ring machine • 93 bunches each • Luminosity • 1033 cm-2 s-1 @1.89GeV • 6 1032 cm-2 s-1 @1.55GeV • 6 1032 cm-2 s-1 @ 2.1GeV • New BESIII • Status and Schedule • Most contracts signed • Linac installed 2004 • Ring installed 2005 • BESIII in place 2006 • Commissioning • BEPCII/BESIII • beginning of 2007 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  40. Backup Slides

  41. Exclusive branching fractions +0.07 –0.01 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  42. Measurements of g in B± decays • Do Dalitz plot analyses to improve the measurement of g using B±DoK± decays, for example Do Ksp+p- • Measurement of relative strong decay phase used in ADS method using B±DoK± decays, where, for example, the interference between Do K+p- and DCSD decays is used • Measurement of relative strong decay phase used in B±DoK± decays, where Do K*±Km is used • Important to measure g this way and Bs DsK±, because one uses Bs mixing and the other is mostly tree level so if different would point directly to new physics source FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  43. Other Items Useful for B decays • Measurement of semileptonic decay form-factors that will allow use of exclusive B decays to measure Vub with good precision via “double ratios” • Much improved absolute branching ratios • Measurement of strong phase used in Do-Do mixing • Measurement of inclusive decay rates FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  44. Are Babar & Belle compatible? • Different rB values generate very different errors. If rB is fixed are results for g compatible? Babar Belle DK : +0.036 rB = 0.21 ± 0.08 ± 0.03 ± 0.04 rB = 0.118 ± 0.079 ± 0.034 –0.034 B = ( 157 ± 19 ± 11 ± 21 )° B = ( 104 ± 45 )° +17 +16 –21 –24 +0.030 +0.029 D*K : rB*= 0.169 ± 0.096 rB*= 0.12 +0.16± 0.02 ± 0.04 -0.11 –0.028 –0.026 B*= ( 296 ± 41 ± 15 )° +14 B*= ( 321 ± 57 ± 11 ± 21 )° –12  = ( 70 ± 31 ) °  = ( 68 +14 13 11 ) ° +12 +14 -15 –10 –11 syst. Dalitz stat. syst. Dalitz stat. DK* : rB(K*)= 0.25 +0.17±0.09 ±0.04 ±0.08 -0.18 B(K*)= ( 353 ±35 ±8 ±21 ±49 )° = ( 112 ±35 ±9 ±11 ±8)° FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  45. Measuring d at CLEO-c • For C=-1 DoDo states such as the y • Thus by using both z=-1 & z=+1 & the fact that r has been measured, cosd can be determined • For C=+1 DoDo states • Here y and cosd are coupled See Gronau, Grossman & Rosner hep-ph/0103110] FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  46. ADS Method for Measuring g • ADS: Atwood, Duniez & Soni Phys. Rev. Lett. 78, 3257 (1997) • This is based on an older method of Gronau, London & Wyler that is more difficult to apply Phys. Lett. B253, 483 (1991); Phys. Lett. B265, 172 (1991); Gronau, Phys. Lett. B557, 198 (2003) • Consider B-DoK- & B-DoK- where the Do again goes to states fi common to both Do & Do. These can be states like K-p+ which interfere due to DCSD or even CP eigenstates, but they can’t all be CP eigenstates or we are back in the realm of GLW FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  47. Measuring d at CLEO-c • For C=-1 DoDo states such as the y • Thus by using both z=-1 & z=+1 & the fact that r has been measured, cosd can be determined • For C=+1 DoDo states • Here y and cosd are coupled See Gronau, Grossman & Rosner hep-ph/0103110] FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  48. Problem: how many events? • Fits to Asymmetric signal function (Crystal Ball shape) plus smooth background shape (ARGUS function) – error in tags ±0.3% FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  49. ADS Method for Measuring g • ADS: Atwood, Duniez & Soni Phys. Rev. Lett. 78, 3257 (1997) • This is based on an older method of Gronau, London & Wyler that is more difficult to apply Phys. Lett. B253, 483 (1991); Phys. Lett. B265, 172 (1991); Gronau, Phys. Lett. B557, 198 (2003) • Consider B-DoK- & B-DoK- where the Do again goes to states fi common to both Do & Do. These can be states like K-p+ which interfere due to DCSD or even CP eigenstates, but they can’t all be CP eigenstates or we are back in the realm of GLW FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

  50. What about fDs? • CLEO-c will start scan to determine best place to run for Ds now; will also measure B(Dsfp+) • Old determinations of fDS are too poor to use 201 FLAVOUR IN THE ERA OF THE LHC, Nov. 7-10, 2005

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