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Measuring the J / -Nucleon dissociation cross section with PANDA . - - PowerPoint PPT Presentation

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Measuring the J / -Nucleon dissociation cross section with PANDA . Bhler 1 P on behalf of PANDA collaboration 1 Stefan Meyer Institute, Vienna logo P . Bhler (SMI) Hadron 2011, 14.06.2011 1 / 15 Motivation J / -nucleon

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Measuring the J/Ψ-Nucleon dissociation cross section with PANDA

P . Bühler1

  • n behalf of

PANDA collaboration

1Stefan Meyer Institute, Vienna P . Bühler (SMI) Hadron 2011, 14.06.2011 1 / 15

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Motivation

J/Ψ-nucleon dissociation cross: Probability of J/Ψ to break up when moving through nuclear matter. Charme in medium - fundamental parameter Issue in heavy ion research Anomalous suppression observed in central HI collisions Probable indication of existence of Quark-Gluon-Plasma

P . Bühler (SMI) Hadron 2011, 14.06.2011 2 / 15

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Experimental approaches

Nucleus (Z,A) J/Ψin J/Ψout σdiss

P . Bühler (SMI) Hadron 2011, 14.06.2011 3 / 15

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Experimental approaches

Nucleus (Z,A) σdiss J/Ψout

P . Bühler (SMI) Hadron 2011, 14.06.2011 3 / 15

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Experimental approaches

Nucleus (Z,A) p(400GeV) J/Ψout σdiss

NA50 collaboration, Eur. Phys.J.C 48 (2006) 329 Production of J/Ψ Interpretation of results ambiguous because mixed with

  • ther effects

Large momenta, feed down from

  • ther states, interaction with

co-movers

✞ ✝ ☎ ✆

σdiss ≈ 4.5 mb (1 − 7 mb)

P . Bühler (SMI) Hadron 2011, 14.06.2011 3 / 15

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Experimental approaches

Nucleus (Z,A) p(Eres) J/Ψout σdiss

K.K. Seth, A Unique way to Measure Charmonium-Nucleon Cross Sections, Hirschegg, 2001 Formation of J/Ψ Avoid effects from large momenta, feed down, co-movers

✄ ✂

  • ✁

At FAIR with PANDA

P . Bühler (SMI) Hadron 2011, 14.06.2011 3 / 15

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Measurement of σdiss

Nucleus (Z,A) p(Eres) PFermi J/Ψout σdiss #in #form #esc, #obs

#esc = #form · (1 − σdiss · ρL) σdiss = 1 ρL · » 1 − #esc #form – modeling measurement #obs = #esc · br · feff #form = F(., ., ., .) · #in

P . Bühler (SMI) Hadron 2011, 14.06.2011 4 / 15

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HESR and PANDA at FAIR

HESR Pp: 1.5 - 15 GeV/c HI and HR mode

∆Pp Pp ≥ 2 · 10−5

L ≤ 1032 1/cm2/s PANDA 4π coverage Charged and neutral particle identification Cluster jet and solid targets

P . Bühler (SMI) Hadron 2011, 14.06.2011 5 / 15

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Questions to answer

How can #in be determined How can #esc be measured How accurately can #form and ρL be computed

P . Bühler (SMI) Hadron 2011, 14.06.2011 6 / 15

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Measurement of #esc

p + A → J/Ψ → l+l− cross sections in the order of 100 pb total cross section in the order of 1 b → need background suppression of > 1010 exploit topology of signal events to enhance S/N Combination of cuts allows to efficiently suppress background (< 10−10)

PANDA Physics Performance Report, arXiv:0903.3905

How long will it take?

◮ σobs ≈ 100 pb, L ≈ 1030

✞ ✝ ☎ ✆

→ a few J/Ψ per day!

P . Bühler (SMI) Hadron 2011, 14.06.2011 7 / 15

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Computation of #form

ideal case: ∆Pp = 0, Pp = 0 σBW(Ecm) = 2J + 1 (2S1 + 1)(2S2 + 1) 4π k2

  • (Γ/2)2

(Ecm − mJ/Ψ)2 + (Γ/2)2

  • BinBout

mJ/Ψ = 3096.916 ± 0.011 MeV, Γ = 0.0932 ± 0.0021 MeV

(Particle Data Group, Physics Letters B667, 1 (2008)

BinBout = (1.14 ± 0.2) × 10−4

(E760 collaboration, Phys. Rev. D 47 (1993) 772)

→ BW(mJ/Ψ) = 280 nb

P . Bühler (SMI) Hadron 2011, 14.06.2011 8 / 15

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Computation of #form

  • 1. complication: ∆Pp = 0

[%]

res

P )

res

  • P

p

(P

  • 0.1
  • 0.05

0.05 0.1 relative

  • 3

10

  • 2

10

  • 1

10 1 )

p

BW(P HI mode HR mode

  • 2. complication: Nuclear binding

energy, in-medium mass shift?

[GeV/c]

res

p

P 4.06 4.07 4.08 4.09 4.1 4.11 Atomic mass A 50 100 150 200

  • 3. complication: Pp = 0, Fermi

motion PF = (3π2 Z

V )1/3 ≈ 250MeV/c

P . Bühler (SMI) Hadron 2011, 14.06.2011 9 / 15

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Computation of #form

p Nucleus

P . Bühler (SMI) Hadron 2011, 14.06.2011 10 / 15

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Computation of #form

p

r [fm] 1 2 3 4 5 6 ]

  • 3

(r) [fm ρ 0.05 0.1 0.15 0.2 A = 56 3pG 2pF I 2pF II normal nuclear density

  • H. de Vries et al. Atomic Data and Nuclear Tables 36 (1987) 495

Nucleus

P . Bühler (SMI) Hadron 2011, 14.06.2011 10 / 15

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Computation of #form

p

r [fm] 1 2 3 4 5 6 ]

  • 3

(r) [fm ρ 0.05 0.1 0.15 0.2 A = 56 3pG 2pF I 2pF II normal nuclear density

  • H. de Vries et al. Atomic Data and Nuclear Tables 36 (1987) 495
  • 6
  • 4
  • 2

2 4 6

Nucleus xf dxf ∝ dN/dz

P . Bühler (SMI) Hadron 2011, 14.06.2011 10 / 15

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Computation of #form

p

r [fm] 1 2 3 4 5 6 ]

  • 3

(r) [fm ρ 0.05 0.1 0.15 0.2 A = 56 3pG 2pF I 2pF II normal nuclear density

  • H. de Vries et al. Atomic Data and Nuclear Tables 36 (1987) 495
  • 6
  • 4
  • 2

2 4 6 pF [MeV/c] 50 100 150 200 250 300 normalized distribution 0.002 0.004 0.006 0.008 0.01

A = 40 dN/dz

PF ∝ ρ1/3 Nucleus xf dxf ∝ dN/dz

P . Bühler (SMI) Hadron 2011, 14.06.2011 10 / 15

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Computation of #form

p

r [fm] 1 2 3 4 5 6 ]

  • 3

(r) [fm ρ 0.05 0.1 0.15 0.2 A = 56 3pG 2pF I 2pF II normal nuclear density

  • H. de Vries et al. Atomic Data and Nuclear Tables 36 (1987) 495

pF [MeV/c] 50 100 150 200 250 300 normalized distribution 0.002 0.004 0.006 0.008 0.01 A = 40 dN/dz

PF ∝ ρ1/3

  • 6
  • 4
  • 2

2 4 6

PJ/Ψ = Pp + PF fdiss ∝ rA

xf ρ(l)dl

Nucleus xf dxf ∝ dN/dz

P . Bühler (SMI) Hadron 2011, 14.06.2011 10 / 15

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Computation of #form

[GeV] S 3.095 3.0955 3.096 3.0965 3.097 3.0975 normalized distribution 0.2 0.4 0.6 0.8 1 1.2 A = 40 )

Ψ J/

BW(m = 0

p

P ∆ = 0,

p

P ∆ = 0

p

P ∆ HR mode, = 0

p

P ∆ HI mode,

F

= P

p

P ∆ HR mode,

F

= P

p

P ∆ HI mode, momentum [GeV/c] p 4.11 4.112 4.114 4.116 4.118

res

BW

/#

esc

# 1 1.5 2 2.5 3 3.5 4

  • 3

10 × A = 40 HI mode HR mode

First step in simulations more sophisticated models required

P . Bühler (SMI) Hadron 2011, 14.06.2011 11 / 15

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Computation of ρL

σdiss = 1 ρL ·

  • 1 − #esc

#form

  • modeling

measurement

A 50 100 150 200 p cross section p fraction of

  • 3

10

  • 2

10

  • 1

10 1 p cross section p according to formed escaped P . Bühler (SMI) Hadron 2011, 14.06.2011 12 / 15

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Computation of ρL

ρL = ∞

xf ρ(l)dl

  • depends on

. ρ(r) . distribution of formation points, d(xf) . Fermi-momentum distribution

compute by MC with high statistics

P . Bühler (SMI) Hadron 2011, 14.06.2011 13 / 15

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Computation of ρL

σdiss = 1 ρL ·

  • 1 − #esc

#form

  • 1/3

A 2.5 3 3.5 4 4.5 5 5.5 6 <rho.L> [1/fm^2] 0.2 0.4 0.6 0.8 1 1.2

dN/dz <rho.L> = -2.23e-01 + 1.76e-01 * A^(1/3)

P . Bühler (SMI) Hadron 2011, 14.06.2011 14 / 15

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Computation of ρL

σdiss · ρL =

  • 1 − #esc

#form

  • 1/3

A 2.5 3 3.5 4 4.5 5 5.5 6 <rho.L> [1/fm^2] 0.2 0.4 0.6 0.8 1 1.2

dN/dz <rho.L> = -2.23e-01 + 1.76e-01 * A^(1/3)

1/3

A 2 2.5 3 3.5 4 4.5 5 5.5 6 #form #esc 1 - 0.1 0.2 0.3 0.4 0.5

P . Bühler (SMI) Hadron 2011, 14.06.2011 14 / 15

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Computation of ρL

σdiss · ρL =

  • 1 − #esc

#form

  • 1/3

A 2.5 3 3.5 4 4.5 5 5.5 6 <rho.L> [1/fm^2] 0.2 0.4 0.6 0.8 1 1.2

dN/dz <rho.L> = -2.23e-01 + 1.76e-01 * A^(1/3)

1/3

A 2 2.5 3 3.5 4 4.5 5 5.5 6 #form #esc 1 - 0.1 0.2 0.3 0.4 0.5 <rho.L>(A) × ](A) = 4.24e-01 #form #esc 1 - [

→ σdiss = 4.2 mb

P . Bühler (SMI) Hadron 2011, 14.06.2011 14 / 15

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Summary

With PANDA pA → J/Ψ → l+ + l− can be efficiently measured ≈ a few J/Ψ per day To determine σdiss one needs to

◮ Scan resonance and determine shape and number of J/Ψ (#esc) ◮ Compute number of formed J/Ψ (#form) ◮ Fit

h 1 − #esc

#form

i (A) with ρL (A)

Parameters to select

  • Ppi
  • , HR/HI, {(A, Z)j}

Parameters to measure #in, #esc Parameters to model #form

P . Bühler (SMI) Hadron 2011, 14.06.2011 15 / 15