Charm2006 Beijing 6 June 2006 Jim Russ - Carnegie Mello n 1 New Results on Heavy Flavor New Results on Heavy Flavor Baryons Baryons Charm 2006 Charm 2006 Outline – Qqq Masses and Lifetimes – theoretical issues and new results c mass shift b lifetime Charm baryon lifetime systematics –new data – Qqq Decay and Excitation Properties b Branching Ratios More New c states c Branching Ratio Measurements – QQq States – an update – Conclusions
New Results on Heavy Flavor Baryons Charm 2006. Outline Qqq Masses and Lifetimes – theoretical issues and new results L c mass shift L b lifetime Charm baryon lifetime systematics –new data Qqq Decay and Excitation Properties L b Branching Ratios More New L c states - PowerPoint PPT Presentation
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Charm2006Beijing 6 June 2006
Jim Russ - Carnegie Mellon 1
New Results on Heavy Flavor BaryonsNew Results on Heavy Flavor BaryonsCharm 2006Charm 2006
Outline– Qqq Masses and Lifetimes – theoretical issues and new
resultsc mass shift
b lifetimeCharm baryon lifetime systematics –new data
– Qqq Decay and Excitation Properties b Branching Ratios
More New c states c Branching Ratio Measurements
– QQq States – an update– Conclusions
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A Weighty Matter - What is the A Weighty Matter - What is the cc Mass? Mass?
PDG value static for a decade, dominated by CLEO and NA32 results
New results from BaBar and Selex with much smaller errors pull mass 1.5 MeV/c2 higher
Important information for any future studies of c c resonant production at e+e- machines.
• HQET [ (1 /mQ)2 suppression of non-spectator effects] all B-hadron lifetimes should be very similar. (b
0 )/(d0 ) is well below prediction in LEP, CDF
Run I data.
• Charm baryon lifetime hierarchy predicted from quark models already in 1984-86. HQET agrees.
• Data match HQET except for c+. The ratio (c
+ )/ (c0 ) is
off by the same factor as the lifetime. Problem for HQET: lifetime ratios vary as (1 /mQ)3 while the lifetime itself varies like (1 /mQ)2 .
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Selected Lifetime RatiosSelected Lifetime Ratios
PDG 2005 lifetimes
Theory Data(PDG05)
B+/ B0 1.06 1.086 0.017
bB0 0.9-1.0 0.797
c+/ c
+ 1.5 2.2
c+/ c
0 2.7 2.9
Model calculations describe lifetime systematics well, with two conspicuous problems.
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New New bb0 0 Results from CDF Results from CDF
CDF and D0 measure lifetime using b
0 J First results using fully-reconstructed decays.
New CDF measurement (1 fb-1): = 1.59 (stat)(syst) ps
0 lifetime agrees well with PDG: 1.524 ps
Ratio to 0 Js minimizes systematics:
b / = 1.037
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Restoration of Order in HQET?Restoration of Order in HQET?Bigi and Uraltsev: ‘natural’ range of b / is 0.94 - competing effects from positive and negative interference.
Models enhanced sub-leading terms in 1/mb matrix element expansion faster decay rate. Predictions for b / range from 0.86 to 0.90 in these models.
With this new result, are we back to the basic model for b decays?
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One Disagreement gone – what about One Disagreement gone – what about cc++??
c+)/ c
+) ~ 1.5 in models c
+) ~ 300 fs
CLEO: c+) = 503 fs (250
evts)FOCUS: c
+) = 439 fs (532 evts)
New SELEX Result
SELEX: c+) = 419 fs (301
evts)Excellent agreement with FOCUS
Problem with c+) is not experiment !
SELEX Preliminary
c+)
301 evts
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ccooLifetimeLifetime
FOCUS (180 GeV beam): 59 evts in 2 modes
stat)syst) fs
Using PDG c+ lifetime, the lifetime ratio becomes
(c+)/ c
0)= 2.81 compared with the model prediction of 2.7
SELEX(600 GeV - beam): 76 evts in 2 modes
stat)syst) fs
Recent Results from FOCUS, SELEX
signal backgnds for 2 modes
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Branching Ratio MeasurementsBranching Ratio MeasurementsLifetimes are inclusive calculations. What about BRs, where W-scattering and Pauli Interference terms are important, as in the c
0 system studied in great detail recently by BaBar and Belle
Tevatron, e+ e- B-factories producing new b- and c-baryon branching ratio measurements. Theoretical predictions for some baryon modes
now available from Soft Collinear Effective Theories (SCET).
c0Spectator + Pauli c
0WS + Pauli
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New New bb Branching Ratio Measurements Branching Ratio Measurements
CDF: BR for single-pion emission in Bo and b decays – test of SCET. Note complex background for b. Limiting error comes from the BR for c pK- + , not statistics!
bc+-BoD+ -) = 3.3 0.3(stat) 0.4(sys) 1.1(frag+BR)
while SCET (Leibovich, Ligeti, Stewart and Wise) predicted 1.7 We wish we knew the c pK-+ BR better.
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More SCET TestsMore SCET TestsSCET + HQET + 1/Nc predicts b semileptonic decays dominated by c
+ ground state (6%) + p-wave excitations (2-3% for each state) and predicts that c modes are suppressed.
Predictbc+bc
+-New CDF measurements of these quantities.
Good news for theory: CDF measurement bc
+bc+-stat) 1.2(sys)
1.2(BR)And not so good news – CDF has first measurements of semileptonic decays to excited charm baryon states. Four different channels measured :
bc+(2593)bc
+… not ½ .
bc++ bc
+same order.
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BELLE and BABAR BELLE and BABAR cc00 Studies Studies
BABAR
c0c
0
(stat) (syst)
CLEO(92)
(stat) (syst)Körner and Kramer (92) quark model
0.32 (WS / Spectator)
BELLE
c0KSc
0
(stat) (syst) [1st]Zenczykowski (94) quark model + CA
0.28 (WS + Internal W)/Spectator
Quark Models do pretty well. How can we move beyond them?
For charm SCET arguments break down. Excellent new data on branching ratios is compared to venerable quark models.
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BaBar BaBar cc00 Studies Studies
BaBar reports a lovely c primarily in the two-body decay channel. They report at 90% C.L.This is a surprising result.
For the spin-1/2 charm baryons c
+ and c
+ the 3 relative
branching ratios are of order 3.3!
CLEO and E687(photoproduction) had also reported only an upper limit for Is there something unusual about the spin-3/2 decay mechanism?
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Charm Baryon Spectroscopy – from Charm Baryon Spectroscopy – from harmonic oscillator to the latticeharmonic oscillator to the lattice
• State of the art in spectroscopy still based on Copley, Isgur and Karl from 1979 – valence quarks in harmonic oscillator potential. Model has huge number of states, but only a few are seen.
• New lattice calculation program underway (LHPC, Colin Morningstar) – aims to compute excitation spectra for normal and charmed baryons with dynamic pions as light as 300 MeV. – expect first results in 2007.
• Meanwhile, Belle and Babar report new c and c states.
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Belle Data Show New Belle Data Show New cc State State
c+ +
Reflection from c+(2880)
Quark model calculations predict width ~ 15 MeV/c2
Experimental width ~ 70 MeV/c2
Mixing with other states? nearby c1 ?
Quark model candidate state: c2 D-wave excitation c+ -
c0 c
+ c++
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New New cc++ from BaBar from BaBar
BaBar data show known narrow c(2880) and new c (2940) state, both in pDo (new decay mode for c(2880) ).
New state 6 MeV below pD*o threshold, one pion mass above Belle c(2800) state.
No trace of either state in CDF data with comparable mass resolution.
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Spectroscopy ConclusionsSpectroscopy ConclusionsQuark model spectroscopy accomodates the observed c
+ , c states with
reasonable accuracy. Width predictions generally not good. Fixing quantum numbers is hard. without a model as a guide.
• The 2880 decays both to pDo and c2940 goes only to pDo .
• Lattice gauge calculations are starting to treat low-lying states with almost-physical pions. Data have fascinating regularities as a challenge for theory.
CLEO BELLEBaBar
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Now QQq Baryons Now QQq Baryons
Phys Rev Lett 89 (2002)112001
First QQq candidate comes from baryon beam expt:
• (ccd)+c+ K- Cabibbo-favored spectator
mode
•state seen from p but not
• not seen in FOCUS photoproduction expt
• lifetime is very short – disagrees with extrapolation from single charm
Production cross section is a sizeable fraction of c
+ production – consistent with intrinsic charm model.
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A Different A Different cccc++ Decay Mode Decay Mode
cc+ pD+K-is another ccd
all-charged decay mode.
• Have automatic background check with pD-K+
• Event-mixed background (grn) gives absolutely-normalized description of bkg .
• Wrong-sign pD-K+ are featureless at same level as combinatoric.
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Combine Combine cccc++ Mass Distributions Mass Distributions
Phys. Lett. B628,18 (2005)Gaussian with width fixed from MC fitted to pD+K-data to fix mass: 3518 MeV/c2 .
Combine with 3519 MeV/c2 from other mode:
m(cc+) = 3518.7 MeV/c2
.(pD+K-)/c+K-
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Also a Also a cccc++++ Excited State Candidate Excited State Candidate
Look at Q=2 candidates in c+ K-
final state from - beam. No new cuts.
See broad structure at 3780 MeV/ c2 – wider than resolution – either has natural width or two states
• Combinatoric background from event mixing describes high-mass side of plot
• fitted background under peak compares well with event-mixed level.
• Have one (or maybe HQET pair of) ccu excited state(s).
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BaBar and Belle Null Searches for BaBar and Belle Null Searches for cccc+,+++,++
BaBar sample: 600,000 c+ pK-with PID (DIRC)
BaBar finds no hint of a signal in any double-charm state from continuum annihilation at 10.58 GeV/c and sets a 95% C.L upper limit corresponding to 7% of the production of singly-charmed c
0 -
Belle (Preliminary!) also finds no cc
+ but they report two new c
+ states at 2980 and 3077 MeV/c2 from the search.
higher mass state is narrow. Lattice, where are you?
cx(2980)+
cx(3077)+
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ConclusionsConclusions• Belle and Babar continue CLEO tradition of charmed baryon spectroscopy. New c
+ states not seen in hadron experiments,e.g., CDF.
• CDF has new b0 measurements in fully-reconstructed modes. CDF
lifetime result removes conflict with HQET/1/mQ expansion. Await b
0,- , b- measurements for further tests of lifetimes and SL decay
widths .
• Charm baryon lifetimes agree well with model calculations except for the c
+ . Experiments agree well. Theory???
• New c+ , c
0,+,++ , c+ states from BaBar and Belle challenge lattice
spectroscopy to predict sparse charm baryon mass population.
• SELEX double charm baryons are statistically significant, limited signal populations. Production definitely baryon-baryon – not seen in photoproduction. Intrinsic charm?
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And WishesAnd Wishes• Many Qqq baryon studies hinge on knowing the BR for c pK-
+. I wish for e+e- running at 2mc to nail the BRs.
• Experiment continues to add new Qqq states. I wish for high statistics samples of B decays to c-baryons for JP analysis. Belle has made a start.
• Collider experiments are starting precision tests of SCET and factorization for baryons as well as mesons. I wish for continued developments in theory and data. I hope for the b-c baryon soon to be seen at the Tevatron.
• Double charm studies are still active and point to purely hadron-hadron production. I wish there were future hadron experiments to pursue such issues in flavor physics. (maybe LHCb)