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Charmed Baryon Production (Charmed baryon Spectroscopy via p ( p - , D * - ) Y c ) 11 Sep., 2013 H. Noumi RCNP, Osaka University. What are good building blocks of Hadrons?. Constituent Quark. [ qq ]. ͞ q. ͞ q. q. q. q. q. q. q. hadron (colorless cluster). q. q. q. Diquark ?.

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Charmed Baryon Production(Charmed baryon Spectroscopy via p(p-,D*-)Yc)11 Sep., 2013H. NoumiRCNP, Osaka University

what are good building blocks of hadrons
What aregood building blocks of Hadrons?

Constituent Quark

[qq]

͞q

͞q

q

q

q

q

q

q

hadron (colorless cluster)

q

q

q

Diquark?

(Colored cluster)

how to form baryons
How to form baryons?
  • Most fundamental question
  • Interaction btwn quarks

Diquark correlations

q

q

q

  • 3 [qq]-pairs in a Light Baryon

How to close up diquark correlations

charmed baryon
Charmed Baryon

VCMI~[as/(mimj)]*(li,lj)(si,sj)

  • Weak CMI with a heavy Quark
    • [qq] is well Isolated and developed

qq

  • Level structure of Yc*
  • Decay Width/Decay Branching Ratios, etc.

Q

charmed baryon spectroscopy p50
Charmed Baryon Spectroscopy (P50)

Missing Mass Spectroscopy

Measure D*-

Missing Mass Spectrum

Dispersive

Focal Plane

Hydrogen

Target

K+

20 GeV/c

p-Beam

p-

p-

High-resolution, High-momentum

Beam Line

D*-Spectrometer

charmed baryon spectrometer
Charmed baryon spectrometer

2m

Modified design

FMcyclotron magnet

J-PARC E16

⇒ 2.3Tm, 1 m gap

  • High ratedetectors
    • Fiber, SSD
  • Large detectors
  • Internal detectors
    • DC, RPC
  • PID: RICH
    • Hybrid radiator

Ring Image

Cherenkov

Counter

Internal TOF

FM magnet

ps-

Internal DC

LH2-target

p-

Beam GC

Beam p-

SSD

K+

Fiber tracker

TOF wall

Decay p+

DC

Internal TOF

  • Large acceptance multi-particle spectrometer system
  • Multi propose spectrometer
background reduction 3
Background reduction 3

* D* tagging: > 106reduction

⇒Other event selection

    • Forward scattering angle cut

⇒ Reduction (2.2-3.4 GeV/c2) = 15

  • Signal acceptance = 0.54
  • 1900 → 1000 counts

15×2.0×106reduction

background

W/ signals

Reduction

qpD*

qD0

qD0ps

qps

S/N

qKp

Kpqcm

background spectrum
Background spectrum

Only D* tagging

W/ event selection

Clear peak structure @ 1 nb/peak case

*Main background structure is dominant.

⇒ Achievable sensitivity: 0.1-0.2 nb (3s level, G < 100 MeV)

W/o signal

W/o signal

Sum

Main BG

(s-production

+ Miss-PID)

Associated

charm

production BG

W/ signal: 1000 counts/peak

W/ signal: 1900 counts/peak

decay measurement
Decay measurement

Internal tracker

  • Method: Mainly Forward scattering due Lorentz boost (q<40°)
    • Horizontal direction: Internal tracker and Surrounding TOF wall
    • Vertical direction: Internal tracker and Pole PAD TOF detector
  • Mass resolution: ~ 10 MeV(rms)
    • Only internal detector tracking at the target downstream
  • PID requirement: TOF time difference (p & K) ⇒ DT > 500 ps
    • Decay particle has slow momentum: < 1.0 GeV/c

Magnet pole

Target

Beam

Beam

Target

Magnet pole

Pole PAD TOF wall

Surrounding TOF wall

basic performances
Basic performances

Acceptance: D*- detection

  • Acceptance
    • 50-60%
      • exp(bt) (t-channel, b = 2 GeV-2)
    • Yield @ 1 nb case: ~1900 counts
      • 4 g/cm2LH2 target, 8.64×1013p- (100 days)
      • eall= 0.55
    • Acceptance for decay particles: ~85%
      • Lc(2940)+→ Sc(2455)0 + p+
      • Lc(2940)+→ p + D0

*Compare coverage cosq> -0.5

  • Resolution
    • Dp/p = 0.2% @ 5 GeV/c
    • Invariant massresolution
      • D0: 5.5 MeV
      • Q-Value: 0.7 MeV
    • Missing massresolution
      • Lc+: 16.0 MeV
      • Lc(2880)+: 9.0 MeV
    • Decay measurement
      • DM ~10 MeV

exp(bt)

Isotropic in CM

Decay angle: Lc(2940)+→ Sc(2455)0 + p+

Forward direction

(Beam direction)

tagged missing mass spectra
Tagged missing mass spectra

Sc0 p+

Sc++ p-

SUM

Sc0

*Full event w/ background @ 1 nb

  • Continuum background around the peak region
  • Signal counts
    • Scp mode:~230 counts
    • p D mode: ~320 counts

Sc++

Signal

Main BG

Lc+ p+ p-

p D0

D0

Lc+

tagged missing mass spectra1
Tagged missing mass spectra

Sc0 p+

Sc++ p-

SUM

Sc0

*Full event w/ background @ 1 nb

  • Selecting Lc+p+p- decay chain ⇒ Background level was drastically decreased.
  • Signal counts
    • Scp mode:~230 counts⇒ ~200 counts
    • p D mode: ~320 counts

Sc++

Signal

Main BG

Lc+ p+ p-

p D0

D0

Lc+

what we can learn from p50
What We can Learn from P50…
  • Production Cross Section Not only for feasibility but also…
    • Production Mechanism (Hosaka-san)
      • Does the Regge model work? (large s & small |t|)
        • Coupling Constant/Form Factor -> LQCD?
      • What does the state population tell us?
        • Spin/Isospin Structure
        • Wave Functions (Q-Diq picture or others)
        • So-called rho-mode (di-quark) excitation?
    • Application of pQCD (Kawamura-san)
      • Applicable at large s &|t| (Hard process)?
      • Prediction from pQCD
      • Are there any feedback from the P50 measurement?
what we can learn from p501
What We can Learn from P50…
  • Expected Spectrum
    • Excitation Energy and Width
      • Baryon Structure
      • Can we see a Quark-diquark picture?
  • Decay Property
    • Decay branch/partial width
      • Baryon Structure
        • G(Yc* -> pD)/G(Yc* -> pSc) ?
    • Angular Distribution
      • Spin/Parity
charm production cross section
Charm production Cross Section
  • No exp. data for the p(p-,D*-)Lc is available but σ<7nb at pp=13 GeV/c at BNL (1985)
charm production cross section1
Charm production Cross Section
  • Photoprod. of LcD*barXon p at Eg=20 GeV.
    • s(LcDbarX) =44±7+11-8nb
    • s(D-X)=29±5+7-5nb
    • s(D*-X)=12±2+3-2nb

s(LcD*barX) ~ 18nb

  • This seems sizable.

g

D*

p

LC , X

Abe et al., PRD33, 1(1986)

charm production cross section2
Charm production Cross Section
  • s(pN→J/ψX) =(1±0.6)nb and (3.1±0.6)nb at 16 GeV/c and 22 GeV/c.
    • OZI-suppressed process!

LeBritton et al., PLB81, 401(1979)

J/ψ

p

N

X

comparison in strange sector
Comparison in strange sector
  • OZI-suppressed process in Strange Sector
    • s(p-p→fn) =(1.66±0.32)nb at 4 GeV/c.
    • s(p+p→fp+p) =(9.5±2.0)nb at 3.75 GeV/c

-> s(pN→fN)/s(pN→fX)~1/10?

  • OZI-non-suppressed process
    • s(p-p→K*L) =(53±2)nb at 4.5 GeV/c

-> s(p-p→K*L)/s(pN→fX)~2?

-> ??? s(p-p→D*Lc)/s(pN→J/yX)~2?

Avres et al., PRL32, 1463(1973)

Gidalet al., PRD17, 1256(1978)

Crennell et al., PRD6, 1220(1972)

theoretical estimations
Theoretical Estimations
  • t-channel PS meson exchange
  • Comment on the pQCD model
  • Regge Model: revisit
revisit the regge theory

discussedwith A. Hosaka

Revisit the Regge Theory
  • shows the typical s-dependence of binary reaction cross sections at the large s region;
    • Regge trajectory:
    • scale parameter s0 :

s at the threshold energy of the reaction AB → CD

(*In Kaidalov’s Model: s02(aD*(0)-1)=sCDar(0)-1 *sCDaJ/y(0)-1

sAB=(Σmi)A*(Σmj’)B, mi:transversal masses of the consituent quark)

  • Treatment of G(-a(t)) to avoid possible singularities
    • Actually introduce phenomenological form factor
      • G(-a(t)) →G(-a(t0)): naïve Regge
      • → G(1-a(t0)) : Kaidalov’sRegge[Z. Phys. C12, 63(1982)]
      • → exp(R2t): Grishina’sRegge[EPJ A25, 141(2005)]
regge theory

calculated by A. Hosaka

Regge Theory
  • PS(K,D)-Regge (Top): s/c-prod: ~10-5(Naïve), ~3x10-5(Kaidalov)
  • V(K*,D*)-Regge (Bottom): s/c-prod.: ~10-4(Naïve), ~3x10-5(Kaidalov)

Scale Parameter

s (arb.)

pp=20 GeV/c

pp=20 GeV/c

s/s0

s/s0

Regge Trajectory

s (arb.)

pp=20 GeV/c

pp=20 GeV/c

s/s0

s/s0

regge theory1
Regge Theory
  • Normalization with s(p(p-,K*)L) data [PR163, 1377(1967), PRD6, 1220(1972)]
    • Naïve Regge shows a steeper s-dependence
    • Grishina’sRegge with R2=2.13 GeV-2 reproduces data well.
  • Charm production: ~10-4 of strangeness production,

   → We expect s (p(p-,D*)Lc) close to 10nbat pp=20 GeV/c.

p(p-,K*)L

Ratio of s- to c-prod.

exp(R2t)

s (mb/sr)

exp(R2t)

G(-a(t0))

s(p(p-,K*)L)/ s(p(p-,D*)Lc)

p(p-,D*)Lc

exp(R2t)

G(-a(t0))

G(-a(t0))

s/s0

s/s0

pp=20 GeV/c

pp=20 GeV/c

comment on the coupling constant
Comment on the Coupling Constant
  • Comparison of gD*D*p/gK*K*pandgLcND/gLNK*
    • Estimated by means of the Light Cone QCD Sum Rule
    • Exp. Data
  • Taking gD*D*p/gK*K*p~1, gLcND*/gLNK*~0.67

     → We expect s (p(p-,D*)Lc) ~a fewnb.

M.E. Bracco et al.

Prog. Part Nucl. Phys. 67, 1019(2012)

A. Khodjamirian et al.

EJPA48, 31(2012)

*note:g[Bracco]/2=g[Khodjamirian]

q may isolate qq

Hosaka-san

“Q” may isolate “qq”
  • λ and ρ motions split  known as isotope shift

sqsq, SO

Λc(1/2-,1/2-

3/2-,3/2-, 5/2-)

r

q-q

q-q

q

Σc(1/2-,3/2-)

q

l

ρ mode

Σc(1/2-,1/2-

3/2-,3/2-,5/2-)

q

Q

Q

Λc(1/2-,3/2-)

λ mode

Σc(1/2+,3/2+)

G.S.

Λc(1/2+)

25

excitation energy dependence

discussed by A. Hosaka

Excitation Energy Dependence

f

p

D*

  • Production Rate in a quark-diquark model:
    • D* exchange at a forward angle
    • Radial integral of wave functions

Taking Harmonic Oscillator Wave Functions

      • I~ (qeff/A)Lexp(-qeff2/2A2), where A: oscillator parameter (0.4~0.45 GeV)
      • For larger qeff, the relative rate of a higher L state to the GS increases as ~ (qeff/A)L
    • Spectroscopic Factor: g
      • pick up good/bad diquark configuration in a proton
      • A residual “ud” diquark acts as a spectator
    • Kinematic Factor w/ a propagator :
    • Spin Dependent Coefficient, C:
      • Products of CG coefficients based on quark-diquark spin configuration
      • Characterized by the spin operator in the vector meson exchange,

D*

g

c

u

“ud”

“ud”

p

Yc

  • =1/2 for Lc’s
  • =1/6 for Sc’s
estimated relative yield

calculated by A. Hosaka

Estimated Relative Yield
  • The estimation is valid for the D* exchange at a very forward angle.
  • The yields for some of Sc’s are suppressed due to g and C.
    • The C coefficient is characterized by spin dependent interaction at the D*NYc vertex.
  • Those for Lc’s are not suppressed very much at the excited states.
    • |I| reduces (increases!) an order of (qeff/A)L at higher L states.
estimated relative yield strange sector

calculated by A. Hosaka

Estimated Relative Yield (strange sector)

Exp.: p(p-,K0)Y, D.J. Crennell et al., PRD6, 1220(1972)

  • The yield for S1/2+ is suppressed due to g and C.
  • The estimation is not very far from the experimental data but for S’s.
    • This already suggests a necessary modification of the model.
    • The measurement in charm sector provides valuable information on the reaction mechanism and structure of baryons.
slide30

Lc(1/2-)

Lc(1/2+)

charm

qeff=1.37 GeV/c

qeff=1.33 GeV/c

r {fm}

r {fm}

L(1/2+)

L(1/2-)

strange

qeff=0.27 GeV/c

qeff=0.29 GeV/c

r {fm}

r {fm}

L=0

L=1

summary
Summary…
  • Experimental Design
    • 1000 count/nb/100d
    • Background reduction
      • Signal Sensitivity: 0.1~0.2 nb for G~100 MeV state
      • 1 Decay particle detection inprove S/N very much
    • Improve the acceptance Decay particle Acceptance
  • Production Rate
    • A few nbfor Lc production seems a plausible estimation
  • Excitation Energy Dependence
    • The production rate is kept even at higher L states, depending on spin/isospin structures of baryons.
    • How are the rho-mode states excited?
  • How can we extract “diquark” in baryons
  • Can we can learn characteristic baryon structures from
    • Excitation Energy Spectrum
    • Population (Production Rate)
    • Decay (Partial) Width/Branching Ratio
    • Angular Correlation
    • What is similarity to/difference from strange baryons
structure and decay partial width
Structure and Decay Partial Width

Illustrated

by Hosaka

Excited (qq)

Good [qq]

  • L(1520) -> NK (D wave!)>πS, similarly L(1820), L(2100)
  • Possible explanation of narrow widths of Charmed Baryons
possible subjects
Possible Subjects
  • CharmedBaryon Spectroscopy
  • N*, Y* resonances via (p,ρ), (p,K*)
  • h’, w, f, J/y, D, D* productions off N/A
  • “K-K-pp” strongly interacting hadronic system
  • S=-1, -2, -3 baryonspectroscopy w/ K beam
  • others

We welcome you to join !