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
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
Top Related