Baryon Spectroscopy Results at the Tevatron

Transcription

1 Baryon Spectroscopy Results at the Tevatron XIII International Conference on Hadron Spectroscopy Novemer 9 Decemer 4, 9 Florida State University Rick Van Kooten Indiana University (Representing the CDF & DØ Collaorations)

2 Spectroscopy Spectroscopy at the Tevatron Highest effective collisions energies in world (at least for a little while longer...) Great deal of program focuses on high p physics T Spectroscopy? Rate Access to large masses Focus here (rate still huge for heavy quarks, i.e., c and quarks) (however, need to use relatively rare decays or rare decays of products to ensure that clean enough)

3 Motivation Why Heavy Quark Hadron Spectroscopy? Heavy quark hadrons are the "hydrogen atom" of QCD, and hadrons offer the heaviest quarks in ound systems Very sensitive tests of potential models, HQET, and all regimes of QCD in general, including lattice gauge calculations Decays into heavy quarkonia rich ground for exotics Why at the Tevatron? Decent rates for exotics: Produce heavier states not accessile anywhere else: Complementary to B factories...

4 Motivation Why Heavy Quark Hadron Spectroscopy? Heavy quark hadrons are the "hydrogen atom" of QCD, and hadrons offer the heaviest quarks in ound systems Very sensitive tests of potential models, HQET, and all regimes of QCD in general, including lattice gauge calculations Decays into heavy quarkonia rich ground for exotics Previous talk: Kai Yi Heavy Mesons Outline: Heavy Baryons (not reporting on pentaquarks from ~4...) (apologies to theorists if not comparing to their favorite model)

5 Detectors Relevant for B physics: DØ Tracker: excellent coverage Silicon & scintillating fier & vertexing Small radii, ut extending to h < New Layer silicon on eam pipe in 6, improving impact para. resol. Triggered muon coverage: h < E.g.triggers: dimuons, single muons, track L CDF Tracker: excellent mass resolution Silicon, Layer & vertexing Large radii drift chamer, many hits, excellent momentum resolution de/dx (and TOF): particle id Triggered muon coverage: h < 1 E.g.triggers: dimuons, lepton + displ. track, two displaced tracks

6 Tevatron Luminosity 7 f 1 Range of integrated lumi. reported here Tevatron doing very well, collected > 7 f, expect to more than doule our analyzed data set y end of running in 11 1

7 New Flavored Baryons S S J =1/ Baryons X dd ud uu ds us X W ss X dds n dss X d u s W udd uds L,S uud L,S uss X X p uus S + S Until recently, ground state was the only directly oserved aryon D S * J =3/ Baryons X * ddd dds S X D W * dd X * ds ss W d u s udd uds dss sss S * ud W S us uss X * uu X * D + W X uud uus S *+ uuu S + DØ, CDF D ++

8 New Flavored Baryons S S J =1/ Baryons X dd ud uu ds us X W ss X dds n dss X d u s W udd uds L,S uud L,S uss X X p uus S + S Until recently, ground state was the only directly oserved aryon More statistics, look for other aryon states D S * J =3/ Baryons X * ddd dds S X D W * dd X * ds ss W d u s udd uds dss sss S * ud W S us uss X * uu X * D + W X, uud uus S *+ uuu S + DØ, CDF DØ, CDF DØ, CDF D ++ CDF

9 S Heavy Baryon L= "atomic" system, heavy quark and light diquark : : : uu dd ud q q spin: spin1: tough at Tevatron 3/ + : : qq Predictions from HQET,Lattice QCD, potential models, sum rules: 1/ + : Diquark spin alignment Hyperfine mass splitting Isospin (u, d diff.)

10 S Heavy Baryon p Form a large optimized sample of Strong decay p± K Candidates per MeV/c CDF PRL 99, 1 (7) 1.1 f 1 PV Total Fit Partiallyreconstructed L Fullyreconstructed B Partiallyreconstructed B Cominatorial Data L N( ) = 318 ± L c p m(l c ) GeV/c L L c p Then add a pion Estimate ackgrounds: with random hadronization tracks (89%) other hadrons (~7%) cominatorics (~3%) Fit for Q values and no. of events p +

11 S Heavy Baryon Candidates per 5 MeV/c CDF Data Total Fit Background S * S + S S Candidates / (1 MeV/c Candidates / (1 MeV/c PRL 99, 1 (7) 8 ) 6 4 ) Constrain Two peaks for each charge, 5.s significance w.r.t. no signal Use CDF II measurement of to get asolute masses: Q = m(l p) ) m(l ) m p (MeV/c )

12 S Heavy Baryon Splittings? Diquark spin alignment (Isospin averaged) [1] * * Hyperfine mass splitting Isospin (u, d diff.) [] * PRL 99, 1 (7) [1] Karliner, Lipkin, hepph/3743, PLB 6 (8) 539 [] Karliner, Lipkin, arxiv:

13 Weakly Decaying Baryons Heavy aryon q s W q s s c c Baryon J/y

14 X Heavy Baryon "Strangely Beautiful Baryon" "Triple Scoop Baryon" Quark content: : su : sd CDF, DØ CDF Decays weakly, dominated y quark Lifetime should e comparale to other hadrons DELPHI measured from excess of events Dimuons! ct ~ 5 cm CDF uses silicononly tracking for charged X (first time at a hadron collider) Challenging for track reco. DØ reprocesses tracks using special settings to improve effic. of highimpact parameter tracks CDF vertexing software needed modifications

15 X Heavy Baryon "Strangely Beautiful Baryon" "Triple Scoop Baryon" Quark content: : su : sd CDF, DØ CDF Decays weakly, dominated y quark Lifetime should e comparale to other hadrons DELPHI measured from excess of events Dimuons! ct ~ 5 cm CDF uses silicononly tracking for charged X Candidates / 1 MeV/c 3 1 CDF 1 L~1.9f yield=3,5±34 M=(1,31.37±.4)MeV/c M(Lp ) [GeV/c ] Events/(. GeV) DØ 1 D, 1.3 f rightsign wrongsign (a) M(Lp) [GeV]

16 X Heavy Baryon "Strangely Beautiful Baryon" "Triple Scoop Baryon" Selection: cuts on momenta, vertex quality, decay length DØ: oosted decision tree, opt. ased on wrongsign data, signal MC CDF: use as control sample, replace K with X CDF DØ m m cm X L + m L vtx p1 1 cm p p m J/y L X + p + p + p Run 179, Event 55788, M(X ) = GeV

17 ) Candidates / (15 MeV/c X Heavy Baryon PRL 99, 5 (7) CDF 7.7s PRL 99, 151 (7) 5.5s 5.4 yield=17.5±4.3 M=(5,79.9±.5)MeV/c M(J/yX ) 1 D, 1.3 f Data Fit L~1.9f [GeV/c ] M(X ) (GeV/c ) CDF DØ DØ: many checks that no signal in wrongsign cominations, sideands, sideands CDF also has signal in DØ: lifetime consistent with expectations: Events/(.5 cm) channel 1 DØ, 1.3 f Data signal Data sideand MC signal + data kgd Proper decay length (cm) now updated (later)

18 X Heavy Baryon X Mass DØ PRL99, 51 (7) CDF PRL99, 5 (7) Theory prediction Jenkins PRD54,4515 Karliner et al hepph/ m(x ) [GeV/c ]

19 Baryon...douly strange p Events/(.4 GeV) Summer 8, DØ analysis, 1.3 f uilding on previous oservation PRL 11, 3 (8) D 8 D f f 1 Data 4 Fit M(W ) (GeV) Events/(.4 GeV) Yield 17.8 ± 4.9 ±.8 candidates wrong sign 8 W sideands L sideands Mass (GeV) Likelihood ratio, stat. significance = 5.4s Include "trials" factor, significance = 5.5s Remains > 5s with syst. checks m J/y W Events/(.5 GeV) W m L 1 D, 1.3 f p K Right sign Wrong sign W veto M(LK) (GeV) After special track reprocessing, large impact parameter tracks

20 Baryon PRL 11, 3 (8) Events/(.5 cm) D 1.3 f 1 Data MC signal + data kgd (t = 1.54 ps) Proper decay length (cm) Decay lengths consistent with weakly decaying state (expect GeV ack then) Greater than expected values, careful checks: Mass measurements in MC samples Variation of selection criteria Comparison of data fitted masses of and consistent w/ PDG Rate with respect to also measured (later comparison) X DØ PRL99, 51 (7) CDF PRL99, 5 (7) Mass Theory prediction Jenkins PRD54,4515 Karliner et al hepph/ m(x ) [GeV/c ]

21 Baryon 1964 m p p m + J/y L K W 5 1 cm Run 399, Event 88165, M(W ) = GeV

22 Baryon (plus and Properties) PRD 8, 73 (9) 1 Result from CDF, 4. f, comprehensive reconstruction of hadrons into J/y Control/check Measure SVX +6 Yield: 16 4 evts. Significance: 5.5s (mass and lifetime info, likelihood ratio and toy MC's) ct > 1 mm Long decay lengths (cm) of charged After impact distance reqs. can use silicon tracking to improve impact parameter resolution (acceptance low for )

23 Baryon (plus and Properties) PRD 8, 73 (9) Masses from fit to sample with ct > 1 mm Lifetime from yield in ins of ct (no need to model ackground) Updated First exclusive lifetime! First ever! Relative rates ;

24 Baryon : Comparison Difference of measured masses: DØ: Significant (~6s) disagreement! DØ's largest mass systematic unc. is 1 times less than this difference DØ is working on an update of this measurement with an increased data set that may help address discrepancy. Relative rates: Using ratio of decay partial widths from PRD 56, 799 (1997) + CDF lifetime ratio,

25 Baryon : Comparison Difference of measured masses: Significant (~6s) disagreement! DØ's largest mass systematic unc. is 1 times less than this difference DØ is working on an update of this measurement with an increased data set that may help address discrepancy. Relative rates: DØ: CDF: 1.3s difference (assuming Gaussian unc.)

26 Baryon : Comparison DØ Mass CDF 4. f 1 Events/(.4 GeV) DØ 1.3 f 1 CDF Mass Data Fit M(W ) (GeV)

27 DØ Mass Mass Proper decay length Events/(.4 GeV) D 1.3 f 1 CDF Mass Data Fit M(W ) (GeV)

28 Summary & Prospects Renaissance of heavy quark hadron spectroscopy (and properties) as new massive states continue to e discovered Excellent datatheory agreement for most new heavy aryons > 5s discrepancy etween DØ and CDF mass measurements; CDF measurement consistent with predictions Providing useful input and comparisons to potential models, HQET, lattice gauge calculations, other QCD models: outstanding prospects for continued precision predictions (e.g., inputs for ) Heavy quark and light quark spectroscopy can enefit each other

29 Conclusions & Prospects Next good experimental prospects for aryon spectroscopy? Possiility of doule heavy aryons: among others... Tevatron doing very well, collected > 7 f, expect to more than doule our analyzed data set y end of running in 11 Still statistics limited on most analyses! LHC, ATLAS, CMS 1 q q L= "atomic" system, heavy quark and light diquark Lose heavy quark symmetry, see V. Lyuovitskij's talk ATLAS eam gas event, eam energy 1.18 TeV from yesterday

30 Backup Slides

31 DØ CDF World Averages From Lewis et al., Phys.Rev.D79:145,9 Black hatched: Lattice; Blue oxed: SU(3) symmetry reaking, 1/m q, 1/N c, expansion (Jenkins et al.)