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Another look at Charm: the CLEO-c physics program

Another look at Charm: the CLEO-c physics program. y  D o D o , D o  K - p +. Marina Artuso, Syracuse University. K +. K -. p +. p -. K +. K -. Physics Topics – Overview. Testing the Standard Model CKM Matrix elements

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Another look at Charm: the CLEO-c physics program

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  1. Another look at Charm: the CLEO-c physics program yDoDo, DoK-p+ Marina Artuso, Syracuse University K+ K- p+ p- K+ K- Marina Artuso

  2. Physics Topics – Overview • Testing the Standard Model • CKM Matrix elements • Tests of Theoretical Models necessary to interpret critical CKM data • Tests of theories used to interpret B decay data • Beyond SM possibilities • Mixing • CPV • Rare Decays • Engineering measurements: e. g. absolute B's Marina Artuso

  3. Unique event properties Only DD not DDx produced Can get DoDo, D+D-, DsDs, LcLc Probably other charmed baryons as well (not yet measured) Large cross sections s(DoDo) = 5.8 nb s(D+D-) = 4.2 nb s(Ds Ds) = 0.5 nb Unique Opportunities at Charm Thresholds R (units of s(m+m-)) - + - + - + s(m+m-)= 5.4 nb at 4 GeV Marina Artuso

  4. Kinematical Niceties • Ease of B measurements using "double tags" • BA = # of A/# of D's • # of D's is well determined; continuum data not needed • Backgrounds are miniscule • Possible because • relatively large B (many %), • multiplicities typically small <ncharged> = ~2.5, <npo> ~ 1.2, • high luminosity • System is over constrained if • all particles are observed: • Spi  3, Etot 1, mD=mD 1 Marina Artuso

  5. Leptonic and Semileptonic decays • 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   2 Marina Artuso

  6. The run strategy • Run Plan • 3fb-1 at 3770 (DD production) • 3fb-1 at 4140 (DsDs production) • 1fb-1 at 3100 (J/y production) • 1fb-1 at LcLc threshold • yrunning under study • Some key data Samples • 30MY’’==> ~5 Million tagged D decays • 1.5M DsDs==> ~0.3 Million tagged Ds • 109 J/Y==> ~ 1billion of J/y’s About one year each Marina Artuso

  7. The CESR-c Accelerator • Modify for low-energy operation: addwigglers for transverse cooling • Expected machine performance: • Ebeam ~ 1.2 MeV at J/ Marina Artuso

  8. CLEO III Detector exists! Marina Artuso

  9. Key properties of the CLEO III detector • Excellent tracking • Excellent calorimeter • Excellent particle identification system • Excellent electron identification • m identification at low momenta and at the highest momenta relevant to our studies • Hermetic detector good n reconstruction Marina Artuso

  10. Implications of good PID • At lower momenta, when K’s and p’s are below threshold dE/dx information from drift chamber is excellent • RICH helps in electron ID and m ID at low energies Marina Artuso

  11. RICH Hadron Identification CLEO III Data CLEO III Full GEANT e+e- y DoDo, Do K-p+ eK =98%, fake p=0.2% Marina Artuso

  12. Large Tagged Samples ( 1 D meson fully reconstructed) • Typical charged particle efficiencies ~80% • Typical po efficiencies ~60% • Recall low average multiplicities Reconstructed Events/fb-1Main Modes • #(Do) = 1,600,000 K-p+, K-p+ po, K-p+ p+ p- • #(D+) = 650,000 K-p+ p+, K-p+ p+ po • #(Ds) = 91,000 fp+, K*op+, h()p+(r+) • #(Lc) = 40,000 pK-p+ + + Marina Artuso

  13. CKM Matrix • CKM matrix elements • Does the standard model explain quark mixing? • Must determine magnitude of each matrix element as well as its phase • Charm decays can be used to determine directly Vcd & Vcs, indirectly Vub and contribute to Vcb 1-l2/2 lAl3(r-ih) -l -l2/2 Al2 Al3(1-r-ih) - Al2 1 VCKM =   weak eigenstates mass eigenstates Marina Artuso

  14. CKM Status Artists view of current constraints ±1s bands, not precise • Current measurements • Vcd = .224±.016, from nN, & nN • Vcs= .97±0.11, from W decay • Vub = ?? ~.003±.001 • Vcb = (41.7±1.3±2.3)x10-3, from BD*ln • B mixing measurement needs theoretical calculation of BBfB. • When Bs mixing is measured still need to check BBfB/BBsfBs 2 2 2 Marina Artuso

  15. Leptonic Decays: D l+n Introduction: Pseudoscalar decay constants Q and q can annihilate probability is  to wave function overlap Example p-: _ In general for all pseudoscalars: Marina Artuso

  16. Importance of Measuring fD+ and fD + s • We can compare theoretical calculations of fD to our measurements and gain confidence in theory to predict fB • fB is necessary to translate measurement of Bo-Bo mixing into value for |Vtd|. • If B++ was measured, then we would have a measurement of the product of |Vub| fB. Knowing fB gives Vub • Similarly fDs/fD checks calculations of fBs/fB _ Marina Artuso

  17. Expected leptonic decay branching fractions • We know: fp = 131.73±0.15 MeV fK= 160.6±1.3 MeV fD+ < 290 MeV @ 90% c.l. (Mark III) • The Ds has the largest B, the µ+ rate is ~0.5% • fDs Measured by several groups, best CLEO + Marina Artuso

  18. Summary of fDs measurements • We could run at 4.14 GeV (higher s); with 150x L, more e, project ~1000 events,  1.7% overall error on fDs • At y we can get fD+ with 1-2.3% error • BES in 22 pb-1 at 4.03 GeV found 3 events • There are also two measurements from LEP using Dswith large errors fDs Values from Ds Marina Artuso

  19. Technique at CLEO-c • Fully reconstruct one D • Seek events with only one additional charged track and no additional photons • Compute MM2 • If close to zero then almost certainly we have a m+n decay. • No need to identify muon-helps systematic error • Can identify electrons to check background level • Expect resolution of ~Mpo 2 Marina Artuso

  20. Summary on decay constant reach • If MM2> 0, candidate for t+n • Non SM physics can break m-t universality G(t+n)/G(m+n)  expectations (see Hewett) Marina Artuso

  21. Best way to determine magnitudes of CKM elements, in principle, is to use semileptonic decays Kinematics: Matrix element in terms of form-factors (for DPseudoscalar l+n For l = e, contribution of f-(q2)0, only way to get information on f- is to use l = m, for D decays Semileptonic Decays: formalism Marina Artuso

  22. Semileptonic Decay Studies yDoDo+D+D-Xen From DELCO • RICH can provide p/m separation to ~500 MeV • Decay rate: • Test of models in D decays: predictions of shapes of form factors (for DVector l+n there are 3 form-factors) • To find Vcs & VcdNeed models for ff at one fixed q2 point Marina Artuso

  23. Current Status of D semileptonic decays • Value of |Vcs| f+(0) measured for DKln: 0.79±0.01±0.04 (CLEO) • Shape of f+(q2), given by f+(0)/(1-q2/mp) measured for DKln: mp=2.00±0.12±0.18 GeV 2 • For DK*ln, ratios of form factors at q2=0 : Neither good accuracy nor agreement among experiments • Dpln & Drln: rates to ~20% accuracy Marina Artuso

  24. Goals in Semileptonic Decays • Measure much better DKlnspectrum • Vcd use Dp(r)ln • Vcs use DK(K*)ln measuring ff shapes to distinguish among models & test lattice QCD predictions • Better in ratio Vcd/Vcs • Vcd & Vcs with precise unquenched lattice predictions, + Vcb would provide an important unitarity check • Vub use Drln to get form-factor for Brln, at same v•v point using HQET Marina Artuso

  25. Semileptonic Decays Low Bkg! q2 (GeV2) Form factors: 1% Check theory! U =Emiss - Pmiss Marina Artuso

  26. Semileptonic Decays Decay Mode PDG2000CLEOc (dB/B %) (dB/B%) D0Kln50.36 D0 pln 161.6 D+ pln481.0 D+ rln 36.4 2.4 Ds fln253.1 Vcd, Vcs to ~1.5% Marina Artuso

  27. Tests of Low Energy QCD •  and  Spectroscopy • Masses, spin fine structure • Leptonic widths for S-states. • EM transition form factors • Will run on  resonances winter ’01-summer’02 ~ 4 fb-1 total • Uncover new states of matter • Glueballs G=|gg> • Hybrids H=|gqq> • Requires detailed understanding of ordinary hadron spectrum in 1.5-2.5 GeV mass range. Spectrum of exotica is to QCD what H-atom spectrum is to QED! Calibrate and test theoretical tech. Precision measurement of the bound states of quark-antiquark atoms Marina Artuso

  28. A brief history of Lattice QCD • Invented in 1974 • Stalls for 20 years • Declared dead (Wilson) 1989 • Mid-1990’s: First high-precision results • as(Mz) ~ 2-3% • Mb ~ 5-10% • Wilson retracts (circa 1995) • Current Situation: 10-20% accurate for masses, form factors… • “quenched” • Future (next 2-3 years): 1-2% accuracy for gold-plated calculations (fully “unquenched”) Marina Artuso

  29. Establish: 75 evt’s • Discover/probe b(’), hb • 13000 (1S)b • ~60 (2S)b • (3S): b’, hb • Scans:ee to few % • (n+1S)(n+1S) • ee/ Upsilon Resonances Marina Artuso

  30. A first Look for glue rich states at U(1S) CM-energy • U(1S) gX as a preview of J/YgX • The U(1S) is also glue rich but… • No PWA at U(1S) but we can show existence of states Marina Artuso

  31. Searches for Hybrids and Glueballs in Y radiative decays • Search for states in glue rich environment • B( J/Y -> g X) ~ 6% • Copious source of color singlet gg pairs • JPC=0++,0-+,2++ • Huge statistics allows to perform PWA to get QN of states • Hermetic detector / Low background • Absolute BR’s: pp, KK, pp, hh,…. Marina Artuso

  32. Inclusive Search •  spectrum from J/ X: • 10-4 sensitivity for narrow resonance • Eg: ~25% efficient for fJ(2220) • Suppress hadronic bkg: J/X Marina Artuso

  33. A useful check: look at current 2 g data • Anti-search in glue-poor environment • Eg. e+e- -> e+e-gg -> e+e-X • Compare: gg ->M vs. gg ->G vs. Marina Artuso

  34. Current Status of exotic QCD bound states • Experimental • Far from clear! Looks messy now due to insufficient statistics • List of “glue ball” suspects • h(1400) region • f0(1500) • fJ(1710) • x(2220) or fJ(2220) • Experimental results are contradictory • Sorting it out will be challenging! Marina Artuso

  35. BES 1996 MKIII 1986 Who can catch the fJ(2220)? ?? LEAR 1998 L3 1997 L3 Signal OPAL 1998 Marina Artuso

  36. Today CLEO-C p+p- 74 32000 p 18 13000 K+K- 46 18600 KSKS 23 5300 pp 32 8500  – 5000 fJ(2220): CLEO-c reach Plots show 1/6 CLEO-C assuming BES branching ratio Marina Artuso

  37. Comparison with Other Experiments Physics after 2005 if approval & construction OK. China: BES II is running now. BES II --> BES III upgrade BEPC I --> BEPC II upgrade, ~1032 lumi. Being proposed Marina Artuso

  38. Physics with Hadronic Decays • Precision measurements of Absolute Branching Ratios • Current Status + Marina Artuso

  39. Measurement of Do K-p+ • Method: Detect D*+p+Do, when Do K-p+ and Do  anything. • Problem: Systematic error due to background extrapolation a is  between thrust axis & slow p+ (4 of 8 intervals shown) Marina Artuso

  40. D+K-p+p+ • Method (CLEO): UseD*+p+Do & poD+, assuming ratio of decay widths is given by isospin symmetry (can never be more accurate than Do K-p+) • Method (MKIII): yD+D- full reconstruction, limited by size of data sample From 9.6 pb-1 & detector far inferior to CLEO III Marina Artuso

  41. Obtainable Precision in Do and D+ branching ratios • Mark III: 9.6 pb-1, inferior detector (g’s, PID), Precision statistics limited, small systematic errors • We will have: • 300x more integrated L • higher single D reconstruction e, due to higher g efficiencies & resolution • PID to handle backgrounds • D+K-p+p+ 14% statistical error, we estimate a 0.4% statistical error! Systematic error is 0.6% and background error 0.1%. • Do K-p+ is even better (0.4% statistical, 0.4% systematic and 0.06% background error) Marina Artuso

  42. D+fp+ s • Method: Reconstruct • Observe signal both with & without explict Ds or Do reconstruction • Measure B(Dsfp+)/B(DoK-p+) D*+ *- Ds S all bkgrds Fake D Marina Artuso

  43. LcpK-p+ + • Lower limit: Measure p and L yield in B decays and assume all such production is due to . Find B=(4.14±0.91)% • Upper limit: Measure LcLln, and assume that L saturates the rate (no S, for example). Find B=(7.7±1.5)% • Conclude: 9.7% > B> 3.0% @ 90% c. l. Marina Artuso

  44. J/y m+m- • Systematic error is the limitation. Completely correlated between the two BES measurements, yet PDG averages? • Currently, best way to determine b yields at hadron colliders Marina Artuso

  45. Importance of Precise Absolute Charm B's: |Vcb| • Best way to measure |Vcb| is to use BD*ln • Effective Theory-HQET gives relevant form-factor and method to extract corrections & estimate their errors • Method using inclusive semileptonic decays assumes "duality." (not yet assessed) • Current errors using exclusive decay (CLEO) • Statistical: 4.3%,Systematic: 4.5%,Theory: 4.5% Decrease:  with more databetter B's, eLattice QCD (DoB error is 2.3%)(unquenched) Marina Artuso

  46. Using Lb to find |Vub/Vcb| & |Vcb| • Use of the decay Lb Lcl-n, would provide an important systematic check for the |Vcb| & |Vub/Vcb| determinations • For |Vub/Vcb| this requires • Measure • Precise determination of the absolute Lc branching ratio • For |Vcb| this requires in addition • Knowledge of the Lb production cross-section Marina Artuso

  47. Understanding Two-body Hadronic B Decays • HQET Spin Symmetry test: , since D*+p+Do is most useful mode, this compares Do/D+ absolute rates • Compare BoD(*)+h- and B+D(*)oh- rates to extract color suppressed amplitudes • Test factorization with BoDDs, requires absolute Ds branching ratio Marina Artuso

  48. Charm Content in B Decay • Important for understanding relation between semileptonic B and amount of charm produced in • QCD prediction should be reliable, but (Neubert & Sachrajda, Nucl Phys B483, 339 1997) Marina Artuso

  49. Effects on Z bb and Z cc (Rb & Rc) • Important to ascertain precision electroweak effects. Example, Dunietz et al. hep=ph/9606327 “Discrepanices between SM predictions and measurements of Rc & Rb are investigated. We show that there exisits a discrepancy in two complementary determinations of B(BDX). Reducing BKp  B(DoK-p+) by 15% removes the discrepancy. Since BKp calibrates most charm hadron yields, the reduced value also eliminates the discrepancy between predicted and mesured values of Rc and mitigates a problem in semileptonic B decays… This means that the charm tagging efficiency in Zcc has been underestimated. As a consequence Rb would need to be revised downward. Marina Artuso

  50. Needs at Hadron Colliders • Eventually need to be able to understand Higgs  bb and cc. Modeling of these decays requires knowledge of absolute (and relative) branching ratios • Such “engineering tables” are crucial toward understanding hadronic b and c “backgrounds” at hadron colliders Marina Artuso

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