Matthew Charles, University of Iowa

Transcription

1 Charm Decays in Matthew Charles, University of Iowa Representing the Collaboration The 3nd International Conference on High Energy Physics Beijing August 16, 4 Introduction Search for D l + l [11-964] Measurement of B(D + s D + s π )/B(D + s D + s γ) [11-953] Relative BF and limits for D + sj [1-631] Relative BF of Cabibbo-suppressed Λ + c decay modes [11-963] Study of Ξ c Ω K + and Ξ c Ξ π + [11-938] Summary All results are preliminary. University of Iowa Page 1

2 Charm physics at PEP-II is also a charm factory σ(e + e cc) 1.3 nb σ(e + e bb) 1.1 nb recorded 44.1 fb 1 (on + off resonance) 317 million cc pairs has an extensive charm program. Other talks: Search for D /D mixing: Milind Purohit in HQ6 Search for CP violation in D + K + K π + : Milind Purohit in HQ6 More D sj studies: Valerie Halyo in HS, Stefania Ricciardi in HQ3 D KSπ + π Dalitz (in B ± D ( ) K ± ): Gianluca Cavoto in CP4 B(D s + φπ + ): Stefania Ricciardi in HQ3 τ results moved to talk by Eric Torrence in EW1. University of Iowa Page

3 First topic: Search for D l + l University of Iowa Page 3

4 Motivation In the Standard Model: FCNC modes are suppressed by GIM mechanism: D e + e (B 1 3 ) D µ + µ (B ) c u s,d W W υ l l l + The lepton flavour violating mode D e ± µ is strictly forbidden. Beyond the Standard Model, New Physics may enhance these, e.g., R-parity violating SUSY could increase these: B(D e + e ) up to 1 1 B(D µ + µ ) up to 1 6 B(D e ± µ ) up to 1 6 [Burdman et al, Phys. Rev. D66, 149 ()] University of Iowa Page 4

5 Method Signal box 11.6 fb 1 Sideband Rare decay mode use blind analysis Use modified Feldman-Cousins method 3 1 e + e - preliminary (Conrad et al, Phys. Rev. D 67, 3). Sensitivity stable against downward fluctuations. Place UL on BF relative to D π + π D + D π + tag to improve D purity Events / 3. MeV/c Events /.5 MeV/c µ µ e + µ m(l + l - ) [GeV/c ] University of Iowa Page 5

6 Preliminary upper limits 9% confidence limits D e + e D µ + µ D e ± µ N hh bg. 3.3 ±.3.1 N comb bg. ± ± ±.4 N bg. ± ±.5.1 ±.4 N obs 3 1 UL (1 6 ) Previous UL (1 6 ) Collaboration E791 1 Hera-B E791 1 [1] Phys. Lett. B 46, 41 (1999) [] Phys. Rev. D 68, 9111 (3) University of Iowa Page 6

7 Summary: Improved upper limits on three D l + l modes Next topic: Relative BF of isospin-violating mode D + s D + s π University of Iowa Page 7

8 Introduction D + s D + s π violates isospin conservation, but seen by CLEO. Up-down mass splitting decay via virtual η possible 1 measures B(D + s D + s π )/B(D + s D + s γ) γ selection includes π veto Validation: Also measure B(D D π )/B(D D γ) [1] P. Cho and M. B. Wise, Phys. Rev. D 49, 68 (1994) University of Iowa Page 8

9 ) Entries/(.5 MeV/c Ratio of D Branching Fractions 9.4 fb 1 m(k π + π ) m(k π + ) m(k π + γ) m(k π + ) preliminary D π ) Entries/(.5 MeV/c preliminary D γ m [GeV/c ].1. m [GeV/c ] B(D D π ) B(D D γ) = 1.74 ±. ±.13 PDG 4: 1.63 ±. University of Iowa Page 9

10 Ratio of D + s Branching Fractions 9.4 fb 1 m(k + K π + π ) m(k + K π + ) m(k + K π + γ) m(k + K π + ) ) Entries/(.5 MeV/c 15 preliminary 1 5 D + π s ) Entries/(.5 MeV/c preliminary D + γ s m [GeV/c ] B(Ds + D s + π ) B(Ds + D s + γ).1. m [GeV/c ] =.6 ±.5 ±.6 PDG 4 (CLEO): ±. University of Iowa Page 1

11 Summary: Improved measurement of B(Ds + D s + π )/B(Ds + D s + γ) Next: Inclusive D + sj University of Iowa Page 11

12 Results from 13 fb 1 in this talk: Inclusive D + s π + π Introduction Inclusive neutral modes: D + s π, D + s γ, D + s π γ Inclusive D + s π ± See talk by Stefania Ricciardi (HQ3) for B D + sj See talk by Valerie Halyo (HS) for D + sj masses University of Iowa Page 1

13 D* (317) + sj D + s π + π + D (46) sj D (536) + s1 Clear signals for D sj (46) + and D s1 (536) + No evidence for DsJ(317) + (yield.6 ± 1.8) No narrow structures seen for m >.63 GeV/c University of Iowa Page 13

14 D + s π + D (46) sj D s + π γ phase space D* (317) + sj D s + π 41 MeV wide D (46) sj + + s D*(11) π γ 41 MeV wide + + D*(11) D s s γ + γ Free parameters in fit Combinatorical background Lineshape of lower reflection Mass, magnitude of D sj(317) + Fixed in fit Lineshape of D sj(317) + Lineshape, mass, magnitude of D sj (46) + reflection University of Iowa Page 14

15 D + s γ + D (46) sj D s + γ D sj (46) + D s + γ: 59 ± 46 events DsJ(317) + D s + γ 17 ± 84 events Reflections: D sj(317) + D + s π γ lost D sj (46) + Ds(11) + π γ from Ds(11) + lost γ from π lost University of Iowa Page 15

16 D + s π γ Inclusive three-body mass spectrum: + D (46) sj D s + π γ Yield in this fit is 46 ± 44. Now try to understand structure... University of Iowa Page 16

17 D + s π γ D*(11) s + + D s ( γ + γ ) + γ m = m D + s γ m D s (11)+ +4 < m < +8 MeV/c + D* (317) + D s π +γ sj + D (46) sj D + γ π s < m < + MeV/c 8 < m < 4 MeV/c D sj (46) + D + s γπ signal yield in this fit: 9 ± 9 Signal peak may include contributions from D sj(317) + γ and D s(11) + π. University of Iowa Page 17

18 Charm Decays in Ds+π γ : D fit + D*(317) s D unbinned likelihood fit used Signal components: DsJ (46)+ Ds (11)+ π DsJ (46)+ DsJ (317)+ γ Background components: Combinatorics (D quadratic) Ds (11)+ plus π + D*(11) s DsJ (317)+ plus γ DsJ (46)+ Ds (11)+ π yield from D fit: 66 ± 38 DsJ (46)+ DsJ (317)+ γ yield from D fit: 11 ± 37 University of Iowa Page 18

19 Preliminary BF results B(D sj (46) + D + s γ) B(D sj (46) + D + s π γ) =.375 ±.54 (stat.) ±.57 (syst.) [BELLE:.55 ±.13 ±.8,.38 ±.11 ±.4] B(D sj (46) + D + s π + π ) B(D sj (46) + D + s π γ) =.8 ±.18 (stat.) ±.11 (syst.) [BELLE:.14 ±.4 ±.; CLEO: 9% CL] 95% confidence limits: B(DsJ(317) + D s + γ)/b(dsj(317) + D s + π ) <.17 forbidden if + B(DsJ(317) + D s + π + π )/B(DsJ(317) + D s + π ) <.11 forbidden if + B(D sj (46) + D s + π )/B(D sj (46) + D s + π γ) <. forbidden if 1 + B(D sj (46) + DsJ(317) + γ)/b(d sj (46) + D s + π γ) <.3 For mass results, see talk by Valerie Halyo (HS) For B D + sj results, see talk by Stefania Ricciardi (HQ3) University of Iowa Page 19

20 Isospin of D sj (317)+ D* (317) sj Could D sj(317) + be part of a tetraquark isotriplet? Look in D + s π + and D + s π modes... + D s π No structure observed. I = favoured D* (317) ++ sj + π + D s University of Iowa Page

21 Summary: Updated measurements of D + sj relative BF, limits Isospin favoured for D sj(317) + Next: Relative BF of Cabibbo-suppressed Λ + c decays ΛK + Σ K + ΛK + π + π Σ K + π + π University of Iowa Page 1

22 Introduction Search for Cabibbo-suppressed decays of Λ + c (cud) via Λ, Σ. Tests of decay models with high-statistics sample. Λ pπ Flight distance > mm ±σ mass window Σ Λγ E γ > 1 MeV ±.5σ mass window fb preliminary 3 15 fb -1 preliminary Yield /.5 MeV / c 6 4 Yield / 3 MeV / c (GeV/c ) M (p π - ) M (GeV/c ) M (/\ γ) (/\ ) 15 fb 1 University of Iowa Page

23 Λ + c ΛK + x p >.5, for x p = p / s/4 m Λ + c 15 fb 1 preliminary 14 1 AR 15 fb -1 preliminary Yield / 4 MeV / c Λ + c Σ π + Ξ c Ξ π (GeV/c ) M + (/\ K ) Λ + c ΛK + Λ + c Λπ + B(Λ + c ΛK + )/B(Λ + c Λπ + ) =.44 ±.4(stat.) ±.(sys.) BELLE with x p >.5 [Phys. Lett. B 54, 33 ()]:.74 ±.1 ±.1 Prediction: [T. Upral et al., Phys. Rev. D 49, 3417 (1994)] Naive estimate: tan θ C =.5, plus phase space correction University of Iowa Page 3

24 Λ + c Σ K + x p >.5 15 fb 1 Yield / 5 MeV / c fb -1 preliminary Yield / 5 MeV / c fb -1 preliminary M (Σ + - M (GeV/c ) K ) (Σ ) M (GeV/c ) M (Σ π + ) (Σ ) Λ + c Σ K + Λ + c Σ π + B(Λ + c Σ K + )/B(Λ + c Σ π + ) =.4 ±.5(stat.) ±.4(sys.) BELLE with x p >.6 [Phys. Lett. B 54, 33 ()]:.56 ±.14 ±.8 Prediction : [T. Upral et al., Phys. Rev. D 49, 3417 (1994)] Naive estimate: tan θ C =.5, plus phase space correction University of Iowa Page 4

25 Λ + c Λ(Σ )K + π + π 4 15 fb -1 preliminary x p >.6 15 fb 1 Yield / 1 MeV / c 3 1 Λ + c ΛK + π + π First observation! BF relative to Λ + c Λπ + is:.66 ±.7(stat.) ±.3(sys.) M (GeV/c ) M + (/\ K π+ π-) (/\ ) Yield / 5 MeV / c fb -1 preliminary x p >.6 Λ + c Σ K + π + π UL on BF relative to Λ + c Σ π + 9% C.L M + - M (GeV/c ) ( Σ K π + π - ) (Σ ) Puzzle: Why so suppressed? University of Iowa Page 5

26 Summary: Relative BF of Cabibbo-suppressed Λ + c First observation of Λ + c decays measured ΛK + π + π Next: Ξ c production and decays University of Iowa Page 6

27 Inclusive Ξc production Study Ξc (csd) decays to Ξ π + and Ω K +. Goals: Measure ratio of BF Study p spectrum Ξ c momentum spectrum At Υ (4S): bb, cc Below Υ (4S): cc only Entries/.5 GeV/c bb Signal MC cc P* (GeV/c) University of Iowa Page 7

28 Mass spectra Ξ c Ξ π + Ξ c Ω K + Off-peak 1.7 fb 1 Entries/.5 GeV/c preliminary m(ξ π + ) (GeV/c ) Entries/.5 MeV/c preliminary m(ω K ) (GeV/c ) On-peak 15.4 fb 1 Entries/.5 GeV/c preliminary m(ξ π + ) (GeV/c ) Entries/.5 MeV/c preliminary m(ω K ) (GeV/c ) University of Iowa Page 8

29 Uncorrected p spectra Ξ c Ξ π + Ξ c Ω K + Off-peak 1.7 fb 1 Entries/. GeV/c preliminary uncorrected Entries/.1 GeV/c preliminary uncorrected * p (GeV/c) p* (GeV/c) bb cc bb cc On-peak 15.4 fb 1 Entries/.5 GeV/c preliminary uncorrected Entries/.1 GeV/c preliminary uncorrected * p (GeV/c) p* p* (GeV/c) p* Clear Ξc First observation: B X + Ξc Ω K + mode. production from BB; measurement to follow. (c.f. CLEO: [Phys. Rev. Lett. 79, 3599 (1997)]) University of Iowa Page 9

30 Ratio of branching fractions p > 1.8 GeV/c cut suppresses bb contribution After efficiency correction, obtain preliminary result: B(Ξ c Ω K + ) B(Ξ c Ξ π + ) =.96 ±.18 (stat.) ±.3 (sys.) Significant improvement on previous measurement by CLEO:.5 ±.1 ±.5 [Phys. Lett. B 83, 161 (199)] Reminder: Absolute BF for Ξ c are not known University of Iowa Page 3

31 Summary Lots of charm physics going on at! D l + l search: improved UL on FCNC, GIM-suppressed decays. Improved measurement of isospin-violating B(Ds + D s + π )/B(Ds + D + s γ). Updated measurements of D + sj relative BF. Λ + c relative BF measurements, including first observation of Λ+ c ΛK + π + π Studies of Ξ c production and decay: Observation of (Υ (4S) BB Ξc + X) Improved measurement of B(Ξc Ω K + )/B(Ξc Ξ π + ) University of Iowa Page 31

32 Additional material University of Iowa Page 3

33 Search for D sj(63) + SELEX recently reported the discovery of a heavy state decaying to D + s η and D K + : events / 1 (MeV/c ) SELEX results (hep-ex/4645, submitted to PRL) 5 + a) D s η Mass ± events / 5 (MeV/c ) a) D K + Mass 569.9± ± b) mixed events M = M(K + K - π + η) - M(K + K - π + ) MeV/c 8 b) D K M = M(K - π + K + ) - M(K - π + ) MeV/c D + s η D K + University of Iowa Page 33

34 D + s selection Search for D sj(63) + D + s η 196, D + s B A BAR in 15 fb 1 SELEX: 544 ± 9 D + s University of Iowa Page 34

35 Search for D sj(63) + D + s η Selection of η 3, 9 η in D + s sample at 5, 87 ± 863 η total at SELEX B A BAR events / 4 (MeV/c ) m η ± M(γγ) MeV/c Inclusive η in D + s events at Inclusive η (no D+ s requirement) at SELEX University of Iowa Page 35

36 Correlated production Search for D sj(63) + D + s η B A BAR There is clearly η production in events with D + s candidates. preliminary To check if they are correlated, we look for an excess in the overlap region. Assuming linear mass dependence, excess is N(D + s η) = 11 ± 75 University of Iowa Page 36

37 D + s η: mass spectra Correlated D + s η spectrum SELEX after background subtraction B A BAR events / 1 (MeV/c ) a) D s + η Mass ± b) mixed events M = M(K + K - π + η) - M(K + K - π + ) MeV/c sees no D sj (63)+ in 15 fb 1. University of Iowa Page 37

38 D K + mass spectra (p > 4. GeV/c) SELEX event/5 MeV/c m(d K ) GeV/c preliminary From D above background events / 5 (MeV/c ) a) D K + Mass 569.9± ±1.9 8 b) D K M = M(K - π + K + ) - M(K - π + ) MeV/c sees clear D sj (573) + ; no D sj(63) + in 15 fb 1. University of Iowa Page 38

39 D + K S mass spectrum (p > 4. GeV/c) event/.5 MeV/c preliminary *+ *+ m(d K s )-m(d ) GeV/c sees clear D s1 (536) + ; no D sj(63) + in 15 fb 1. University of Iowa Page 39

40 D l + l search: Selection Main sources of background: 1. Peaking background from D π + π dominant in D µ + µ. Combinatoric background from l + l pairs dominant in D e + e, e ± µ Peaking background is suppressed by strong PID cuts: 95% efficiency per electron,.% pion contamination 6% efficiency per muon,.% pion contamination Combinatoric background is suppressed by kinematic cuts, mainly: Require D + D π + Require ct > for e + e, e ± µ Mass windows on D, D + Selection cuts formally optimized for each decay mode using signal MC. Sideband data for normalization only. University of Iowa Page 4

41 Search for D sj(63) + : selection criteria D + s K + K π + selection: K ± : PID from Cherenkov detector and de/dx (ɛ 85%, π ± contamination < % π ± : PID from Cherenkov detector and de/dx D + s D + s fit probability >.1% trajectory consistent with beamspot Require D + s ( K K + ) or (φπ + ) With these cuts, fit gives m = GeV/c and RMS = 5. GeV/c η γγ selection in D + s events: π veto on γ (reject if p π > 15 MeV/c) Veto γ from D s(11) + D + s γ E γ > 35 MeV E γγ > 1.15 GeV helicity angle <.85 With these cuts, fit gives m = (547.4 ±.5) MeV/c, σ = (17. ±.5) MeV/c. University of Iowa Page 41

42 Search for D sj(63) + : selection criteria D K π + selection: D fit probability > 1.% D trajectory consistent with beamspot D p >.5 GeV/c Mass window: ± MeV/c (D K + ) selection: Fit probability > 1.% p > 4. GeV/c University of Iowa Page 4

43 Search for D sj(63) + : selection criteria D + D π + selection: ±5 MeV/c mass window on D D + fit probability > 1.% D + trajectory consistent with beamspot < (m D π + m D) < MeV/c K S selection: K S fit probability > 1.% ±16 MeV/c mass window Flight length > 1 mm (D + K S) selection: p > 4 GeV/c University of Iowa Page 43

44 Search for D sj(63) + D + s η: Correlated production Background-subtraction of mass spectra: Excess = N 5 1 (N + N 4 + N 6 + N 8 ) (N 1 + N 3 + N 7 + N 9 ) B A BAR University of Iowa Page 44

45 D + s D + s π : Isospin violation Under isospin conservation, D + s D + s π I = I = I = 1 is forbidden. However, because m d m u, a mixing term arises [1] L mixing = µ m d m u 3 So D + s D + s π can proceed via virtual η emission, with the η mixing to a π. η propagator is off-mass-shell decay is suppressed by: [] π η (m d m u )/(m s (m u + m d )/) 1/43.7 [1] P. Cho and M. B. Wise, Phys. Rev. D 49, 68 (1994). [] J. Gasser and H. Leutwyler, Nucl. Phys. B5, 465 (1985). University of Iowa Page 45

46 D + s D + s π : Selection criteria Selection of π Two γ with E lab 45 MeV Shower shape cut on γ (LAT <.55) p of π > 15 Mev/c cos θ H of π <.85 Mass cut on π (variable) Selection of γ E lab 5 MeV E 1 MeV Shower shape cut (LAT <.8) π veto if 115 < m γγ < 155 MeV/c and Eγγ MeV University of Iowa Page 46

47 Systematics for Λ + c ΛK+ π + π Sources of Systematic error B(Λ + c ΛK + ) B(Λ + c Λπ + ) MC Statistics 1.1% 1.6% Λ mass cut.6%.3% P χ Λvertex cut 1.1%.7% Λ flight cut(r) 3-D.% 1.% x p cut 1.1% 1.6% Fitting 5.1% 1.1% MC Modeling - 5.4% ɛ Ratio.8.49 ɛ Ratio (PID Corrected) Tracking -.8% Total Systematic error 5.5% 1.1% B(Λ + c ΛK + π + π ) B(Λ + c Λπ + ) University of Iowa Page 47