Semiexclusive production of vector mesons in proton-proton - - PowerPoint PPT Presentation

SLIDE 1

ANNA CISEK

Semiexclusive production of vector mesons in proton-proton collisions with electromagnetic dissociation of protons Anna Cisek

University of Rzeszow

MESON 2018 - 15th International Workshop on Meson Physics Kraków, 7-12 June 2018

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ANNA CISEK

Outline

1

Introduction Exclusive production of vector meson Diffractive resonance with strong disociation Diffractive partonic with strong disociation Diffractive production with electromagnetic dissociation

2

Semiexclusive production with electromagnetic dissociation Formalism Results Anna Cisek, Wolfgang Schäfer, Antoni Szczurek

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Introduction ANNA CISEK

Introduction

Exclusive production of heavy vector mesons in proton-proton collisions has been studied in rapidyty range y ∼ 2.0 − 4.5 Large rapidity gaps: no exchange of charge or color. t-channel exchanges with the Regge intercept α(0) or spin J ≥ 1. We often have to deal with diffractive reactions which include excitation of incoming protons. Instead of fully inclusive final states: gap cross sections, or even only vetos on additional tracks(!) from a production vertex. Inelastic state of mass MX populates a rapidity interval ∆y ∼ log(M2

X/m2 p).

A background for exclusive production – or a possible signal when looking for large pT vector mesons with a gap.

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Introduction ANNA CISEK

Diagram for exclusive production of vector meson in proton-proton collisions

p1t J/Ψ p2t pvt p p p p t′

1

t′

2

k1 k2 γ Sel tPom p1t J/Ψ p2t pvt p p p p t′

1

t′

2

k1 k2 γ Sel tPom

photon-Pomeron Pomeron-photon

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Introduction ANNA CISEK

Difractive resonance with strong disociation

p p γ p R J/Ψ P p p γ p R J/Ψ P

low pT → Dissociation into nucleon resonances/low mass continuum

• states. Dominated by N∗(1680), JP = 5

2 +, N∗(2220), JP = 9 2 +,

N∗(2700), JP = 13

2 +.

A model by L.L. Jenkovszky, O.E. Kuprash, J.W. Lämsa, V.K. Magas and R. Orava (2011). large pT → Incoherent diffractive photoproduction of J/ψ off partons. Large diffractive masses are possible here.

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Introduction ANNA CISEK

Difractive partonic with strong disociation

p p γ ˆ t p R2 J/Ψ P W Mx2 p p γ ˆ t p R1 J/Ψ P W Mx1

dissociative production of vector mesons at large pT probes the perturbative QCD Pomeron. (Ryskin, Forshaw et al.). An alternative to the “jet - gap - jet” type of processes.

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Introduction ANNA CISEK

Diagrams representation of the electromagnetic excitation

p p γ p X1 J/Ψ p p γ p X2 J/Ψ

The schematic diagrams representation of the electromagnetic excitation of one (left panel) or second (right panel) photon Anna Cisek, Wolfgang Schäfer, Antoni Szczurek

• Phys. Let. B769 (2017) 176

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Semiexclusive production with electromagnetic dissociation ANNA CISEK

Diffractive production with electromagnetic dissociation

The importent property of these processes is that the pγ⋆ → X transition is given by the electromagnetic structure function of protons

The cross section for such proces can be written as: dσ(pp → XVp; s) dyd2p = d2q πq2 F(in)

γ/p(z+, q2) 1

π dσγ∗p→Vp dt (z+s, t = −(q − p)2) +(z+ ↔ z−) z± = e±y

• p2 + m2

V/√s

Generalization of the Weizsäcker-Williams flux to dissociative processes. Must in principle add contributions of longitudinal photons. Negligible for heavy mesons as long as Q2 ≪ m2

V

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Semiexclusive production with electromagnetic dissociation ANNA CISEK

Diffractive production with electromagnetic dissociation

The flux of photons associated with the breakup of protons is calculable in terms of the structure function of protons F(inel)

γ/p (z, q2, M2 X) = αem

π (1 − z)θ(M2

X − M2 thr)

F2(xBj, Q2) M2

X + Q2 − m2 p

· ·

• q2

q2 + z(M2

X − m2 p) + z2m2 p

2 where Q2 = 1 1 − z

• q2 + z(M2

X − m2 p) + z2m2 p

• xBj =

Q2 Q2 + M2

X − m2 p

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Semiexclusive production with electromagnetic dissociation ANNA CISEK

Structure function of protons

Useful fits to F2

• H. Abramowicz, E. M. Levin, A. Levy and U. Maor Phys. Lett.

B269, (1991) 465 F2(x, Q2) = Q2 Q2 + m2

• FP

2 (x, Q2) + FR 2 (x, Q2)

• Useful fits to F2
• R. Fiore, A. Flachi, L. L. Jenkovszky, A. I. Lengyel and V. K.

Magas - Phys. Rev. D70, 054003 (2004) Imα(s) = sδ

n

cn s − sn s Reα(sn) · θ(s − sn) Re α(s) = α(0) + s π PV ∞ ds′ Imα(s′) s′(s′ − s)

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Semiexclusive production with electromagnetic dissociation ANNA CISEK

Structure function of protons

Useful fits to F2

• A. Szczurek, V. Uleshchenko
• Eur. Phys. J. C12 (200) 663-671

FN

2 (x, Q2) = FN,VDM 2

(x, Q2) + FN,part

2

(x, Q2) FN,VDM

2

(x, Q2) = Q2 π

• V

M4

V · σtot VN(s1/2)

γ2

V(Q2 + M2 V)2 · ΩV(x, Q2)

FN,part

2

(x, Q2) = Q2 Q2 + Q2 · Fasymp

2

(¯ x, ¯ Q2)

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Semiexclusive production with electromagnetic dissociation ANNA CISEK

Rapidity distribution- different structure function of proton

y

6 − 4 − 2 − 2 4 6

b) µ )/dy ( φ ( σ d

4 −

10

3 −

10

2 −

10

1 −

10 = 7 TeV s = 10 GeV

X,max

M

ALLM VDM Fiore SU

y

6 − 4 − 2 − 2 4 6

)/dy (nb) Ψ (J/ σ d

1 −

10 1 10 = 7 TeV s = 10 GeV

X,max

M

ALLM VDM Fiore SU

y

6 − 4 − 2 − 2 4 6

)/dy (pb) Υ ( σ d

1 −

10 1 10 = 7 TeV s = 10 GeV

X,max

M

ALLM VDM Fiore SU

y

6 − 4 − 2 − 2 4 6

b) µ )/dy ( φ ( σ d

4 −

10

3 −

10

2 −

10

1 −

10 = 13 TeV s = 10 GeV

X,max

M

ALLM VDM Fiore SU

y

6 − 4 − 2 − 2 4 6

)/dy (nb) Ψ (J/ σ d

1 −

10 1 10 = 13 TeV s = 10 GeV

X,max

M

ALLM VDM Fiore SU

y

6 − 4 − 2 − 2 4 6

)/dy (pb) Υ ( σ d

1 −

10 1 10 = 13 TeV s = 10 GeV

X,max

M

ALLM VDM Fiore SU

preliminary results

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Semiexclusive production with electromagnetic dissociation ANNA CISEK

Transverse momentum distribution- different structure function of proton

(GeV)

t

p

1 2 3 4 5

b/GeV) µ (

t

)/dp φ ( σ d

7 −

10

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 = 7 TeV s = 10 GeV

X,max

M

ALLM Fiore VDM SU

(GeV)

t

p

1 2 3 4 5

(nb/GeV)

t

)/dp Ψ (J/ σ d

3 −

10

2 −

10

1 −

10 1 10

2

10 = 7 TeV s = 10 GeV

X,max

M

ALLM Fiore VDM SU

(GeV)

t

p

1 2 3 4 5

(pb/GeV)

t

)/dp Υ ( σ d

3 −

10

2 −

10

1 −

10 1 10

2

10 = 7 TeV s = 10 GeV

X,max

M

ALLM Fiore VDM SU

(GeV)

t

p

1 2 3 4 5

b/GeV) µ (

t

)/dp φ ( σ d

7 −

10

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 = 13 TeV s = 10 GeV

X,max

M

ALLM Fiore VDM SU

(GeV)

t

p

1 2 3 4 5

(nb/GeV)

t

)/dp Ψ (J/ σ d

3 −

10

2 −

10

1 −

10 1 10

2

10 = 13 TeV s = 10 GeV

X,max

M

ALLM Fiore VDM SU

(GeV)

t

p

1 2 3 4 5

(pb/GeV)

t

)/dp Υ ( σ d

3 −

10

2 −

10

1 −

10 1 10

2

10 = 13 TeV s = 10 GeV

X,max

M

ALLM Fiore VDM SU

preliminary results

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Semiexclusive production with electromagnetic dissociation ANNA CISEK

Rapidity distribution - meson comparison

y

6 − 4 − 2 − 2 4 6

/dy (nb) σ d

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10 = 7 TeV s = 10 GeV

X,max

M ALLM φ Ψ J/ Υ

y

6 − 4 − 2 − 2 4 6

/dy (nb) σ d

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10 = 7 TeV s = 10 GeV

X,max

M Fiore φ Ψ J/ Υ

y

6 − 4 − 2 − 2 4 6

/dy (nb) σ d

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10 = 7 TeV s = 10 GeV

X,max

M SU φ Ψ J/ Υ

y

6 − 4 − 2 − 2 4 6

/dy (nb) σ d

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10 = 13 TeV s = 10 GeV

X,max

M ALLM φ Ψ J/ Υ

y

6 − 4 − 2 − 2 4 6

/dy (nb) σ d

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10 = 13 TeV s = 10 GeV

X,max

M Fiore φ Ψ J/ Υ

y

6 − 4 − 2 − 2 4 6

/dy (nb) σ d

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10 = 13 TeV s = 10 GeV

X,max

M SU φ Ψ J/ Υ

preliminary results

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SLIDE 15

Semiexclusive production with electromagnetic dissociation ANNA CISEK

Transverse momentum distribution

(GeV)

t

p

2 4 6 8 10

(nb/GeV)

t

/dp σ d

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10

= 7 TeV s = 10 GeV

X,max

M ALLM φ Ψ J/ Υ

(GeV)

t

p

2 4 6 8 10

(nb/GeV)

t

/dp σ d

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10

= 7 TeV s = 10 GeV

X,max

M Fiore φ Ψ J/ Υ

(GeV)

t

p

2 4 6 8 10

(nb/GeV)

t

/dp σ d

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10

= 13 TeV s = 10 GeV

X,max

M ALLM φ Ψ J/ Υ

(GeV)

t

p

2 4 6 8 10

(nb/GeV)

t

/dp σ d

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10

= 13 TeV s = 10 GeV

X,max

M Fiore φ Ψ J/ Υ

preliminary results

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Semiexclusive production with electromagnetic dissociation ANNA CISEK

Rapidity distribution, √s = 7 TeV - different mechanism comparison

y

• 6
• 4
• 2

2 4 6

/dy (nb) σ d

• 3

10

• 2

10

• 1

10 1 10

2

10

3

10

= 7 TeV s = 2 GeV

X,max

M

• Diff. partonic
• Diff. resonance

EM Fiore EM ALLM Exclusive

y

• 6
• 4
• 2

2 4 6

/dy (nb) σ d

• 3

10

• 2

10

• 1

10 1 10

2

10

3

10

= 7 TeV s = 5 GeV

X,max

M

• Diff. partonic
• Diff. resonance

EM Fiore EM ALLM Exclusive

y

• 6
• 4
• 2

2 4 6

/dy (nb) σ d

• 3

10

• 2

10

• 1

10 1 10

2

10

3

10

= 7 TeV s = 10 GeV

X,max

M

• Diff. partonic
• Diff. resonance

EM Fiore EM ALLM Exclusive

Rapidity distribution of J/ψ mesons produced when one of the protons is excited due to photon or Pomeron exchange. Both contributions (one or second proton excitation) are added together. We also show a reference distribution for the pp → ppJ/ψ exclusive process with parameters taken from Anna Cisek, Wolfgang Schäfer, Antoni Szczurek: JHEP 1504 (2015) 159. Anna Cisek, Wolfgang Schäfer, Antoni Szczurek

• Phys. Let. B769 (2017) 176

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Semiexclusive production with electromagnetic dissociation ANNA CISEK

Transverse momentum - mechanism comparision

)

2

(GeV

2 t

p

2 4 6 8 10

)

2

(nb/GeV

2 t

/dp σ d

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10 1 10

2

10

3

10

= 7 TeV s = 2 GeV

X,max

M 2.0 < y < 4.5

• Diff. partonic
• Diff. resonance

EM Fiore EM ALLM Exclusive

)

2

(GeV

2 t

p

2 4 6 8 10

)

2

(nb/GeV

2 t

/dp σ d

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10 1 10

2

10

3

10

= 7 TeV s = 5 GeV

X,max

M 2.0 < y < 4.5

• Diff. partonic
• Diff. resonance

EM Fiore EM ALLM Exclusive

)

2

(GeV

2 t

p

2 4 6 8 10

)

2

(nb/GeV

2 t

/dp σ d

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10 1 10

2

10

3

10

= 7 TeV s = 10 GeV

X,max

M 2.0 < y < 4.5

• Diff. partonic
• Diff. resonance

EM Fiore EM ALLM Exclusive

)

2

(GeV

2 t

p

2 4 6 8 10

)

2

(nb/GeV

2 t

/dp σ d

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10 1 10

2

10

3

10

= 13 TeV s = 2 GeV

X,max

M 2.0 < y < 4.5

• Diff. partonic
• Diff. resonance

EM Fiore EM ALLM Exclusive

)

2

(GeV

2 t

p

2 4 6 8 10

)

2

(nb/GeV

2 t

/dp σ d

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10 1 10

2

10

3

10

= 13 TeV s = 5 GeV

X,max

M 2.0 < y < 4.5

• Diff. partonic
• Diff. resonance

EM Fiore EM ALLM Exclusive

)

2

(GeV

2 t

p

2 4 6 8 10

)

2

(nb/GeV

2 t

/dp σ d

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10 1 10

2

10

3

10

= 13 TeV s = 10 GeV

X,max

M 2.0 < y < 4.5

• Diff. partonic
• Diff. resonance

EM Fiore EM ALLM Exclusive

Anna Cisek, Wolfgang Schäfer, Antoni Szczurek

• Phys. Let. B769 (2017) 176

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Semiexclusive production with electromagnetic dissociation ANNA CISEK

Conclusions

In γ-Pomeron fusion reactions in proton-proton scattering, electromagnetic dissociation is of the same size as strong, diffractive dissociation. It even dominates in some regions of the phase space. Electromagnetic dissociation is calculable from F2 data. Resonance excitation is important at low excited masses. Diffractive dissociation requires modelling, there is only little data to constrain it. The resonance contribution is concentrated at very small t, similar to the coherent elastic contribution

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