Production rates of

Strange and Charmed baryons at Belle

1

string

@s = 10.52 GeV

Nuclear physics consortium

Production rate of hadrons

2

Slope of meson (qqbar) is different from baryons (qqq).

Slope depends on quark counting

“4 or 5-quark state” do not lie on “3-quark state”?

L(1405), pentaquark, Q+?

Production rate s/shad/(2J+1) exp(-amh) due to linear potential

mh(mass of hadrons)[GeV]

s/s h

ad/(

2J+1

)

3

s/s h

ad/(

2J+1

)

Mass of baryons (GeV)

Previous data

deviate

ARGUSs=10.5 GeV

Belle

L(g.s.)/L(1520) deviate in LEP good di-quark > bad di-quark?

L(1520)[3/2-] deviates in ARGUS [3/2-] state is special? L=0 ≠ L=1 ? L(1520) [3/2-] Lc*(2625)[3/2-] L(1405) [1/2-] Lc*(2595)[1/2-]

LEP s=92 GeV

R.L.Jaffe, Phys.Rept.409:1-45,2005

Error bar in ARGUS is large

More precise data

No series of charmed baryon First systematic measurement of production rate for charmed baryons.

4

qq

q

• Interaction between quarks• Diquark correlations

Charmed baryon (Lc[udc], Sc [udc])

Diquark correlation is enhanced by weak Color Magnetic Interaction with a heavy quark

mu, md << mc diquark + quark (qq) (Q)

qq ( ) S=0 “good” diquark qq ( ) S=1 “bad” diquark

Q

q q

Diquark picture

Strange baryons (L[uds], S[uds])

mu, md ≈ ms (qqq) uniform

Strange baryon & Charmed baryon

5

L, S Lc, Sc

[qqs] uniform diquark + Quark [qq] [c]

Strange baryons Charmed baryons

Lc > Sc

good di-quark > bad di-quarkdue to strong attractive force of good diquark

L S

ud

s

ud

s c c

L L

u du d

S=0 S=1 S=0 S=1

6

Systematic study of baryons to search for “exotic” baryons in strange and charmed baryons.

Information on diquark picture of charmed baryons in contrast with strange baryons.

L, S, S*, X, W , Lc, Lc* ,Sc ,Sc

*

First systematic measurement for series of charmed baryons.

It is interesting and important to look at the tendency of many baryons by precise measurement. Belle data, well constructed detectors and good statistics.

In this work

Silicon Vertex Detector

Central Drift Chamber

Aerogel CerenkovTime Of Flight CsI calorimeter

S.C. solenoid

1.5T

KL μ system

8GeV e-

3.5GeV e+

Data of Belle

Integrated luminosity 79.366 fb-1 @ s = 10.52 GeV 702.623 fb-1 @ s = 10.58 GeV ϒ(4S)

7

Good vertex reconstruction

SSD placed in 3cm/2cm from Interaction point (IP), and low materials. Resolution of reconstructed vertex for B J/Psi Ks is about 80 mm.Good for hyperon (long life) reconstruction.

Profile of interaction point (IP)

8

Hyperon reconstruction

Dx

IPInteraction point

p

p-

momentum vector of L

Decay processes •L p p -

•S0 Lg•S*(1385)+ Lp+

p+

or g

(S0 ) (S

*+ )

ct=7.89cm

IP

X-/W-

ct = 4.91cm / 2.64cm

Lct = 7.89cm

p-

p p-

p+ for Wc0

Decay processes•X- Lp - 　　　　　　　•W - LK-

•W c0 W -p+

9

L

Mass spectrum of L

L + Lbar = 373.9 ± 0.5 pb

“Inclusive” total cross sectionFeed down processes from higher states

ds/d

x p

Xp

L / Lbar

Scaled momentum, xp = pc.m. / pc.m. : momentum of baryons s : beam total energy M : mass of baryons

preliminary

10

Mass spectra

real data events in 0.3 < xp <0.4

real data events in 0.3 < xp <0.4

S0(1192) Lg(BR~100%) S*(1383)+ Lp+

(BR=87%)

11

“Inclusive” cross sections vs. xp

12

S0 +c.c. S*+ +c.c.

Xp Xp

preliminary

ds/d

x p

ds/d

x p

S0 + S0 = 97.0 ± 1.5 pb S* + S* = 33.2 ± 2.4 pb

Inclusive total cross section Inclusive total cross section

direct cross section of L• feed-down were subtracted from inclusive cross sections.• Isospin symmetry was assumed for S* and X production cross-sections.

Result

-23.6 8.0 pb

(inclusive)

13

direct S0 and S*+ production• feed-down were subtracted from inclusive cross sections.• Isospin symmetry was assumed for S* and X production cross-sections.

Result

S*+ + c.c. (direct) : 33.2 ± 2.4 pb S*+ + c.c. (inclusive) - 0.4 ± 0.06 pb L(1520) + c.c. = 32.8 ± 2.4 pb

14

L(1520)

15

Select p and K- from IP with cuts for distance from IP ○○　 (4S) data▽▽　 Continuum data　 Y / anti-Y

preliminary

BR=22.5%L(1520)pK-

Mass spectrum of L(1520)

Direct cross section L(1520)

16

L(1520)+c.c. (direct) = 15.3 ± 0.5 pb inclusive – 0.34 ± 0.17 pb Lc

+ = 15.0 ± 0.26 pb

Mass spectrum of X- and W-

17

X- W-

Cross sections of X and W

18

X / X W / W

X + Xbar inclusive cross section = 25.55 +- 0.64 pb

W + Wbar inclusive cross section = 1.15 +- 0.32 pb

●●　＠ 10.58, (4S) data○○　＠ 10.52, Continuum data　 Y / anti-Y

preliminary

Wc W-p+ +c.c.

19

s x BR (W-p+) + c.c. = 0.04 0.003 pb Wc W-X = 0.2 pb

BR 1.25±0.5% for W-X 0.25±0.12% for W-p+

by phenomenological calculation (ref. PDG)

Even

t rat

e / L

int.

Coun

ts

preliminary

Mass [GeV] xp

Lc+, Lc

*+, Sc0, and Sc

*0

Decay process analyzed in this work• Lc

+ pK-p +

• Lc*(2625) Lc

+ p+ p-

• Sc0 Lc

+ p -

• Sc*(2520) Lc

+ p -

+ c.c.

Lc+

Mass plot

Mass spectrum of pKp

20

21

Lc+(2625)

○○　 (4S) data▽▽　 Continuum data　 Y / anti-Y

Xp

ds/d

x p(nb)

preliminary

Lc(2595)+

Lc(2625)+

Lc+(2625)

Mass spectrum

Mass spectrum

22

Sc(2455)0

Sc(2520)0

Lc+ p - decay processes

Exclude in analysis•Lc*(2595)+ Lc

+ p+ p-

•Lc*(2625)+ Lc+ p+ p-

23

○○　 (4S) data▽▽　 Continuum data Y / anti-Y

Sc0(2520)

preliminary

Sc0(2455)

preliminary

Cross sections

direct Lc and Sc production

24

• Lc+ + c.c. (direct)

= 189 ± 66 pb inclusive - (17.9 ± 6.0 pb ) x 3 Sc

0,+,++(2455) + c.c. - (18.8 ± 6.4 pb) x 3 Sc

0,+,++(2520) + c.c. - (31.3 ± 10 pb) 　　　 Lc

+(2625) + c.c. = 47.6 ± 16.2 pb• Sc

0(2455) +c.c. (direct) = 17.9 ± 6.0 pb• Sc

0(2520) + c.c. (direct) = 18.8 ± 6.4 pb• Lc

+(2625) + c.c. (direct) = 31.3± 10 pb

Λc(2595) and Λc(2775) feed downare included.

Result and discussion

25

Previous Belle work

This work (very preliminary)ARGUS

Mass dependence strange ≠ charm not lie on the same line Large discrepancy to ARGUS on L, and S* treatment of feed down?

Deviation of L(1520)[3/2-] is not clear.

W < L, S, X W[sss] with “ “ no good diquark

s/s h

ad/(

2J+1

)

Mass of baryons (GeV)

26

Charmed baryons do not lie on “one” line. Jp : no measurement or not well measured quark-model prediction

Lc > Sc

good diquark > bad diquarkLarge rate of Lc(2625)[3/2-](L=1 state)

Prefer [3/2-] or L=1? Why?Rate of L(1520)[3/2-] is not large. Rates of Lc(2595)[1/2-](L=1 state)

and L(1405)[1/2-] are “key”.

Wc : no measurement of BR a plot with BR(0.24+-0.12%) by the phenomenological calculation. Production rate BR

Lc(g.s)[1/2+]

Lc(2625)[3/2-]

Sc0(2455)[1/2+]

Sc0(2520)[3/2+]

Sc(2800)[??] use 3/2

s/s h

ad/(

2J+1

)

Mass of baryons (GeV)

Charmed baryons

Wc

Results and discussion

Very preliminary

States

27

L [1/2+]L(1405) [1/2-] L(1520) [3/2-]

S [1/2+] S(1385) [3/2+]

X [1/2+] X(1530) [3/2+]

W [3/2+]

Lc+ [1/2+]

Lc(2595)+ [1/2-] Lc(2625)+ [3/2-]

Sc(2455) [1/2+] Sc(2520) [3/2+]

Xc [1/2+] Xc*

W c [1/2+] W c

*On going Unknown J, BR

M(Xp)

28

X(1530)

Xc

Production rates

29

s/s h

ad/(

2J+1

)

Mass – Mass(g.s.) [GeV/c2]

Summary

We measure production rates of strange and charmed baryons at s = 10.52 GeV at Belle.“Systematic” study provides information on quark structure of hadrons. Configuration and performance of Belle detector is good for long-life particles like L, X, and W.　We observed ‘charmed baryons do not lie on one line’.

Can we explain by a diquark picture? Feed down processes Further study of many baryons with various spin-parity

is interesting to see their quark structures.

30