Heavy flavor baryons

transcript

Heavy flavor baryonsRoman Mizuk (ITEP, Moscow)

LP07, August 13-18, 2007, Daegu, Korea

charm and beauty baryonspentaquark searches

Belle Collaboration

Reminder on Heavy Quark Baryons

Total space-flavor-spin wave functionmust be symmetric

similar multiplets if c quark is exchanged by b quark

S-wave

8 S-wave isospin multiplets, 35 P-wave, 85 D-wave,..

Baryons made from u,d,s,c quarks

One heavy quark –

symmetric 6Fantisymmetric 3F

slight=0 slight=1

JP=1/2+ JP=1/2+ or 3/2+

Heavy Quark Symmetry jlight decouples excitation spectra are independent of heavy quark flavor

Simplification: Heavy quark - light diquark picture. Laboratory to test QCD.

example

exact for mQ →

Charmed baryons Beauty baryons

Experimental Status

2 years ago

Experimental Status

Many new states observed recently at

B-factories TEVATRONImportant ingredients

PID, high momentum detached vertex

Λcc[ud]

Observation of Λc(2940)+ by BaBar

Σc(2455)π→Λc+π+π-

Λc(2880)

Λc(2940)Λc(2765)

BaBar: no isospin partners in D+p 2880, 2940 are isoscalars

PRL98,262001

Λc(2880)

Λc(2940)NEW

PRL98,012001

D0 sidebands

wrong-sign combinationsNew decay mechanism: heavy quark → meson.

Belle confirmed

Λc(2940)+ mass is 5MeV below D*p threshold molecule?

He, Li, Liu, Zeng, hep-ph/0606015

CLEOΛcπ+π-

Measurements of M and Γ are consistent

Exotics?

( mass, decay pattern)Chen, Chua, PRD75, 094017 (2007)Garcilazo, Vijande, Valcarce, JPG34, 961 (2007)Chen, Chen, Liu, Deng, Zhu, PRD75, 094017 (2007)

More experimental studies to discriminate.

Conventional baryon? JP=5/2-, 1/2+, 3/2+,..

Γ(Σc*π):Γ(Σcπ):Γ(D0p), …

Λc(2880)+ spin-parity from Belle

helicity angle

J=5/2 is favored over 3/2 (4.5σ) or 1/2 (5.4σ)

@ leading Regge trajectory with Λc+ 1/2+ and Λc(2625)+ 3/2-

m(Λcπ)

Σc(2520) evidence

Σc(2455)

PRL98,262001

Angular analysis of Λc(2880)→Σc(2455)π

Heavy Quark Symmetry:5/2- R=1.45/2+ R~0.3

Capstick, Isgur PRD34,2809 (1986)Quark Model:

5/2- 2900 31307/2- 31255/2+ 2910 31407/2+ 3175

Resonant structure of Λc(2880)→Λc+π+π-

0.03 0.06 0.23](2455)

(2520) Rc

Chen, Chua, PRD75, 094017 (2007)

Selem, Wilczek, hep-ph/0602128predicted in string theory

5/2+ is favored over 5/2-

Λc(2880)+ is likely 5/2+

Σccdd, c{ud}, cuu

Observation of Σc(2800) isotriplet by Belle

Mass, width Σc(2800) can be 3/2- (?)

Mass of Σc(2800) is at D0p threshold.

Pirjol,PRD56,5487 (1997)

PRL94,122002Λc+π- Λc

+π0 Λc+π+

Σc(2800)+

Σc(2800)++

Σc(2800)0

Feed-down from Λc(2880)+→Σcπ→Λc+π+π-

feed-downfeed-down

Measurements of M, Γ and σ are consistent

Capstick, Isgur, PRD34,2809 (1986)More experimental studies to confirm JP.

Ξccsd, csu

Observation of Ξc(2980) and Ξc(3080) by Belle

resonant structure

Mass D-wave excitations ?Ξc(2980) 1/2+, 3/2+,.. Ξc(3080) 5/2+,..

BaBar confirmed also Ξc(3080)0

Λc+K-π+

Ξc(3080)+

Λc+K-π+

Ξc(2980)+

Ξc(3080)+

Ξc(2980)+

Λc+Ksπ-

Ξc(3080)0 NEW

PRL97,162001 hep-ex/0607042

BaBar confirmed

Measurements of M and Γ are consistent

New decay mechanism:s-quark → meson.

More experimental studies to assign JP.

Rosner JPG34,S127 (2007)Chen, Chua, PRD75, 094017 (2007)Garcilazo, Vijande, Valcarce, JPG34, 961 (2007)Chen, Chen, Liu, Deng, Zhu, PRD75, 094017 (2007)Ebert, Faustov, Galkin, arXiv:0705.2957

Evidence for Ξc(3055) and Ξc(3123) from BaBar

Ξc(3080)+

Ξc(2980)+

Σc(2455)++K-→Λc+K-π+

Σc(2520)++K-→Λc+K-π+

Ξc(3055)+

Ξc(3123)+

evidence

hep-ex/... (preliminary)

More experimental studies to assign JP.

Presented at EPS-HEP 2007

Study of B+→Λc+Λc

-K+ by BaBar

B+→Λc+Λc

-K+ decay has been observed by Belle

BaBar: confirmation, resonant structure.

Λc+K-

BaBar “More data are needed before firm conclusions can be drawn.”

Excited Ξc? not seen in continuum

Λc+ Λc

mbc (GeV/c2)

B- meson

confirmed

PRL97,202003 (2006)

phase-space

sidebands

Ωccss

Observation of Ωc* by BaBar

significance 5.2σ Ωc0

Ωc* NEW

Last unobserved ground state charmed baryon.

m(Ωc*) – m(Ωc) = (70.8 ± 1.0 ± 1.1) MeV/c2

PRL97,232001

Comparison with predictions

Rosner, PRD52, 6461 (1995)Spin-flavor wave-functions

Ebert et al, PRD72,034026 (2005)QM with heavy-quark-light-diquark

Burakovsky et al, PRD56, 7124 (1997)Regge framework

Lichtenberg et al, PRD53, 6678 (1996)Mass sum rules

Martin et al, PLB355, 345 (1995)potential model

m(Ωc*) – m(Ωc)

Result

Mathur et al, PRD66,014502 (2002)Lattice NRQCD (quenched)

Roncaglia et al, PRD52,1722 (1995)Feynman-Hellman theorem

Jenkins, PRD54, 4515 (1996)1/MQ and 1/Nc expansion

Savage, PLB359, 189 (1995)Chiral Perturbation Theory

Good agreement

Σbbdd, b{ud}, buu

Blind signal region

arXiv:0706.3868

Λb0π+

Λb0π-

Λb0→Λc

Observation of Σb and Σb* by CDFarXiv:0706.3868

BG fixed

arXiv:0706.3868

Λb0π+

Λb0π-

Λb0→Λc

Observation of Σb and Σb* by CDFarXiv:0706.3868

BG fixed

arXiv:0706.3868

Fix all widths:

Λb0π+

Λb0π-

Σb*-NEW

Σb-NEW

Σb*+NEW

Σb+NEW

Results (MeV/c2):

Korner et al, PPNP33,787

Λb0π+

Λb0π-

Λb0→Λc

Observation of Σb and Σb* by CDF

Fix shape and normalization of bg.

Significance >5.2σ (4 peaks vs. BG only)Each peak >3 σ (except Σb

arXiv:0706.3868

BG fixed

arXiv:0706.3868

Fix all widths:

Λb0π+

Λb0π-

Σb*-NEW

Σb-NEW

Σb*+NEW

Σb+NEW

Results (MeV/c2):

Korner et al, PPNP33,787

Λb0π+

Λb0π-

Λb0→Λc

Observation of Σb and Σb* by CDF

Fix shape and normalization of bg.

Significance >5.2σ (4 peaks vs. BG only)Each peak >3 σ (except Σb

Comparison with predictions

Mathur et al, PRD66,014502 (2002)Lattice NRQCD (quenched)

Karliner, Lipkin, PLB575,249 (2003)QM

Roncaglia et al, PRD52,1722 (1995)Feynman-Hellman theoremCapstick, Isgur, PRD34,2809 (1986)

relativised QM

m(Σb)–m(Λb) m(Σb*)–m(Σb)

Jenkins, PRD54, 4515 (1996)1/MQ and 1/Nc expansion

Ebert et al, PRD72,034026 (2005)QM with heavy-quark-light-diquark

Good agreement

m(Σb–) – m(Σb

+) = 5-7 MeVexpect

arXiv:0706.3868

Ξbbsd, bsu

Observation of Ξb- by D0 and CDF

arXiv:0706.1690 J/ψ Ξ- J/ψ Ξ-

arXiv:0707.0589

Lattice QCD QM HQET

Comparison with predictionsMass measurements are consistent

Ξb-→ J/ψ Ξ-

Good agreement

PRL99,052001 PRL99,052002

(syst) (stat) 0.09 0.28)/()() /()( 0.09

0.08 -

JBRbfJBRbf

Proper decay time distribution consistent with expected Ξb lifetime

Ground state SU(3) multiplets of charmed baryons are complete.

Flood of highly excited charmed baryons.

Summary on Heavy Quark Baryons

Λc(2880)

Σc(2800)

Ξc(3080)

Ξc(2980)

Ξc(3055)

Λc(2940)

CLEOBelleBaBar

New era in beauty baryon

spectroscopy.

Reminder on Pentaquarks

Repeat measurements with high statistics

+ LEPS– CLAS – Belle + SVD-2

Group Reaction σ’sLEPS C K+K- X 4.6DIANA K+Xe K0p Xe’ 4.4CLAS-d d K+K-p(n) 5.2SAPHIR p K+K0(n) 4.8ITEP- A K0p X 6.7CLAS-p p + K-K+(n) 7.8HERMES e+d K0p X ~5ZEUS e+p e’K0p X ~5SVD-2 pA K0pX 5.5TOF pp K0p+ 4-6

Θ(1540)+ predicted in Chiral Soliton ModelObserved in γn→Θ+K- → (K+n)K- and K+n→Θ+→pKS

M ~ 1540 MeV/c2

Γ < 1 MeVLow Γ and M are difficult to explain

Θ(1540)+ |uudds>

Initial evidence:

Also many null results, not easily comparable.

Introduction to Pentaquarks

Repeat measurements with high statistics

+ LEPS– CLAS – Belle + SVD-2

Group Reaction σ’sLEPS C K+K- X 4.6DIANA K+Xe K0p Xe’ 4.4CLAS-d d K+K-p(n) 5.2SAPHIR p K+K0(n) 4.8ITEP- A K0p X 6.7CLAS-p p + K-K+(n) 7.8HERMES e+d K0p X ~5ZEUS e+p e’K0p X ~5SVD-2 pA K0pX 5.5TOF pp K0p+ 4-6

PDG2006NEW?

Θ(1540)+ predicted in Chiral Soliton ModelObserved in γn→Θ+K- → (K+n)K- and K+n→Θ+→pKS

M ~ 1540 MeV/c2

Γ < 1 MeVLow Γ and M are difficult to explain

Θ(1540)+ |uudds>

Initial evidence:

Also many null results, not easily comparable.

Statistics x1.6 Θ(1540)+ signal confirmed, significance increased from 4.4 to 5.3σ

MC verified on tagged kaon data at Belle

New DIANA result

NEW estimation of Θ(1540)+ width

K+ Xe → p KS Xe’

AssumptionΓ, MeV

DIANA BelleNuclear suppression

is the same for Θ+ and nonresonant K0p

0.9 ± 0.3 <0.64

No nuclear suppression for Θ+ 0.36 ± 0.11 <0.28 ?

my estimate

Contradiction with Belle persists (2.2σ, 2.4%)Inelastic Θ(1540)+ production will decrease Belle upper limit

M(pKS)

DIANA finds no Θ+ signal for pK+>525MeV

445<pK+<525MeV

pK+>525MeV 2.9σ fluctuation, decreases significance of DIANA signal

17 events expected-3 found

Evidence for Θ(1540)+ from DIANA is weak.

PAN70,35 (2007)

NOMAD Preliminary

New NOMAD result

N → Θ+X

For large part of xF range NOMAD and ITEP- results are in conflict.

based on subsaple

Upper Limit on Θ+ production rate per interaction vs. xF

NOMAD result can be compared with ITEP- result

Θ+ production rate ~10-3

Θ(1540)+ signal is not confirmed

EPJC49,499 (2007)

New COSY-TOF results

In previous analysis background was underestimated significance lower than claimed.

PLB649,252 (2007)

Statistics x10, improved detection capability Θ(1540)+ signal not confirmed

pp → pK0Σ+

Evidence for Θ(1540)+ from COSY-TOF is negated.

Previous Comparison

Background shape from new data.

New H1 resultep → pKSX No Θ+ signal

H1 result can be compared with ZEUS result

H1 and ZEUS results are in conflict.

Extrapolated to ZEUS y-region.

(preliminary) Q2>20GeV2, 0.04<y<0.95

M(pKS)

PLB639,202 (2006)

Statistics x8 Θ(1540)+ signal confirmed, significance increased from 5.5 to ~8σ

SVD-2 result: the most significant Θ+ signalpA → KSpX

KS decays inside / outsideVertex Detector

M(pKS)

SVD-2 result strongly contradicts HERA-B, CDF.

Θ(1540)+ is produced with small xF

Group σ[Θ(1540)+] / σ[Λ(1520)]

s, GeV

SVD-2 8-12% 12

HERA-B <2% at 95% C.L. 40

CDF <3% at 90% C.L. 2000

For central production difference in energy should not be important.

M(pKS)

M = 1523 MeV= 12 MeVNevnt = 165

M = 1522 MeV= 12 MeVNevnt = 205

hep-ex/0509033

Other new results on pentaquarks

KEK-PS E522PLB635,72(2006)

“Search for Θ+ via π-p→K-X reaction near threshold”

OBELIX (LEAR,CERN)NPA779,116(2006)

“Search for the Θ+ pentaquark in antiproton 4He annihilation at rest”.

CLASPRL97,032001(2006)

“Search for the Θ+ pentaquark in the γd→ΛnK+ reaction measured at CLAS”

CLASPRD74,032001(2006)

“Search for the Θ+ pentaquark in the reactions γp→K0K+n and γp→K0K0p ”

FOCUSPLB639,604(2006)

“Search for a pentaquark decaying to pKS”

DELPHIarXiv:0708.0415

Search for Pentaquarks in the Hadronic Decays of the Z Boson with the DELPHI Detector”

2.5σ signal at M=1530MeV

No new positive results for doubly strange pentaquark Φ(1860) or charmed pentaquark Θc(3100)0.“No stars” in PDG2006 not discussed here.

No significant Θ+ signals.

Summary on Θ(1540)+

For experiment with positive result experiment with similar conditions but null result.

Group Reaction σ’s

LEPS C K+K- X 4.6

LEPS d pK- XDIANA K+Xe K0p Xe’ 4.4

CLAS-d d K+K-p(n) 5.2

SAPHIR p K+K0(n) 4.8

ITEP- A K0p X 6.7

CLAS-p p + K-K+(n) 7.8

HERMES e+d K0p X ~5

ZEUS e+p e’K0p X ~5

SVD-2 pA K0pX 5.5

TOF pp K0p+ 4-6

Evidence for Θ(1540)+ pentaquark is weak

Not a single convincing evidence for Θ(1540)+

unpublished~5σ New data are taken (2007).

Statistics x3.~5σ

In conflict with NOMAD.

Not accessible in new data (energy too low).

Contradicts BaBar eBe→pKSX (statistics x100 larger).

In conflict with H1.

~8σ Contradicts HERA-B, CDF.

5.4σ Contradiction with Belle persists.

unpublished

Conclusions

Experimental evidence for pentaquarks is weakMore null results since PDG2006: COSY-TOF, H1, NOMAD, ...Very low Θ+ width: DIANA Γ = (0.36 ± 0.11) MeV

New results are expected from LEPS, HERA-II.

Impressive progress in heavy flavor baryons# charmed baryons 12 → 18# beauty baryons 1 → 4Λc(2880)+, Ωc*, Σb, Σb*, Ξb provide important constraints for theory. To use other new states: Λc(2940), Σc(2800), Ξc(2980), Ξc(3055), Ξc(3080), we need symbiosis between theory and experiment.

Experiments are consistent and experimental results are robust.

over last 2 years

New challenges for theory?

Back-up

Doubly charmed baryons

Λc+K-π+ Ξc

+π+π-

New decay channel.

+ K- +

Selex’s cc(3520)+ is found neither in c+ K- + nor in c

+ K- +

cc+ cc

also not seen in photo production (FOCUS)

hep-ex/0702001

Not confirmed by BaBar and Belle.

Heavy flavor baryons

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