charmonium production in ultra-peripheral heavy-ion ...€¦ · charmonium production in...

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charmonium production in ultra-peripheral heavy-ion collisions at LHCb Quark Matter 2018, Venezia, Italia Albert Frithjof Bursche 1 , on behalf of the LHCb collaboration. 14 th May 2018 1 Universit` a degli Studi di Cagliari and INFN Cagliari, Italy

Transcript of charmonium production in ultra-peripheral heavy-ion ...€¦ · charmonium production in...

Page 1: charmonium production in ultra-peripheral heavy-ion ...€¦ · charmonium production in ultra-peripheral heavy-ion collisions at LHCb Quark Matter 2018, Venezia, Italia Albert Frithjof

charmonium production in ultra-peripheral heavy-ion

collisions at LHCbQuark Matter 2018, Venezia, Italia

Albert Frithjof Bursche1, on behalf of the LHCb collaboration.

14th May 2018

1Universita degli Studi di Cagliari and INFN Cagliari, Italy

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experimental setup LHCb detector

LHCb experiment

z

y

VELO TT T1-3 Muon-System

IP

Albert Bursche UPC J/ψ 14th May 2018 2 / 14

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experimental setup LHCb detector

LHCb experiment

z

y

VELO TT T1-3 Muon-System

IP

Kaon Identificationε ≈ 90%, mis-ID< 5%

Muon Identificationε ≈ 97%, mis-ID≈ 0.7% athigh pT

Acceptance 2 < η < 5

Albert Bursche UPC J/ψ 14th May 2018 2 / 14

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experimental setup LHCb detector

LHCb experiment

z

y

VELO TT T1-3 Muon-System

IP optimal µ p,K±, π± produced inside the VELO

ok K 0S , Λ0, γ, e±, π0

challenging stable neutral hadrons n, K 0L

Albert Bursche UPC J/ψ 14th May 2018 2 / 14

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analysis introduction

event selection

J/ψ →µ+µ− events with no additional activityfrom the same vertexmuon selection

pTµ > 500 MeV2.0 < ηµ < 4.5

J/ψ selectionpTJ/ψ < 1 GeV

Using data taken in lead-lead collisions at√sNN = 5.02 TeV in 2015

Albert Bursche UPC J/ψ 14th May 2018 3 / 14

b>R +R

Z

Z

A B

diagram from Phys.Rept. 458 (2008) 1-171

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analysis introduction

introduction

(a)

t

AγW

A A

A A

γ ψJ/

Albert Bursche UPC J/ψ 14th May 2018 4 / 14

diagrams from Cepila, Jan et al. Phys.Rev. C97 (2018) no.2, 024901

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analysis introduction

introduction

(b)

t

AγW

A A

A(*)

A

γ ψJ/

Albert Bursche UPC J/ψ 14th May 2018 4 / 14

diagrams from Cepila, Jan et al. Phys.Rev. C97 (2018) no.2, 024901

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analysis introduction

introduction

(a)

t

AγW

A A

A A

γ ψJ/

Albert Bursche UPC J/ψ 14th May 2018 4 / 14

Sensitive to gluons at lowBjorken-x , nuclear PDFs,saturation physics,colour glass condensate

diagrams from Cepila, Jan et al. Phys.Rev. C97 (2018) no.2, 024901

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analysis signal determination

mass fit

invariant mass fit discriminate γ γ →µ+µ− process from J/ψ production

non-resonant Exponential times straight lineJ/ψ Double sided Crystal Ball function

ψ(2S) Double sided Crystal Ball function with all parameters apart fromnormalisation and mean constrained to be identical to J/ψ

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analysis signal determination

the mass fit

Dimuon mass [MeV]3000 3500 4000

Eve

nts

/ ( 1

3 M

eV )

1−10

1

10

210

310 LHCb Preliminary = 5 TeVNNsPb-Pb

data(1S)ψJ/

(2S)ψnon-resonantsum

Albert Bursche UPC J/ψ 14th May 2018 6 / 14

LHCb-CONF-2018-003

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analysis signal determination

transverse momentum fit

transverse momentum fit to determine the number of coherent events

non-resonant STARlight template, normalisation is fixed by Gaussian constraintto the result of the mass fit

incoherent J/ψ production STARlight template, this also accounts for feeddownψ(2S) →J/ψ X

coherent J/ψ production STARlight template

The STARlight templates are from the generated events smeared with aresolution model

~pµ = G (px , 10MeV)~ex + G (py , 10MeV)~ey + G (pz , 10MeV)~ez (1)

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analysis signal determination

the transverse momentum fit

10− 5− 0)2/GeV2

Tlog(p

0

10

20

30

40

50

Eve

nts

/ 0.1

5 data

coherent

incoherent+feed-down

non-resonant

sum

LHCb Preliminary = 5 TeVNNsPb-Pb

Albert Bursche UPC J/ψ 14th May 2018 8 / 14

LHCb-CONF-2018-003

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analysis result

differential coherent cross section

LHCb preliminaryσ = 5.27± 0.21± 0.49± 0.68mb

The analysis is repeated inbins of half unit rapidity yJ/ψ

Uncertainties for statistics,systematic and luminosity areof comparable magnitude

The LHCb acceptance isinteresting to discriminatebetween the models 0 1 2 3 4 5

ψJ/y

00.5

11.5

22.5

33.5

44.5

5

[m

b]ψ

J//d

yσd

Guzey et al.

LTA_W

LTA_S

EPS09

Goncalves et al

IP-SAT

IIM

Cepila et al.

GG-hs

GS-hs

=5 TeVNNsPb-Pb

LHCb Preliminary

Albert Bursche UPC J/ψ 14th May 2018 9 / 14

LHCb-CONF-2018-003

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analysis systematic uncertainties

systematic uncertainties

Source Relative uncertainty (%)Selection efficiency 3.2Reconstruction efficiency 2.1− 4.5Hardware trigger efficiency 3.0Software trigger efficiency 1.6− 5.3Momentum smearing model 3.3Mass fit model 3.9Feed-down background 5.8Branching fraction 0.6Luminosity 13.0

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LHCb-CONF-2018-003

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analysis HeRSCheL - forward scintillators

HeRSCHeL - forward scintillators

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analysis HeRSCheL - forward scintillators

HeRSCHeL - forward scintillators

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analysis HeRSCheL - forward scintillators

HeRSCheL concept

If the nucleon breaks up it will leave debris in5.0 < η < 7.5

Extend present LHCb to observe this debris

Much easier than proton taggers inside thebeam pipe (“Roman Pots”)

illu

stra

tion

Melody Ravonel Salzgeber: 29.09.2016

Melody Ravonel Salzgeber: 29.09.2016

Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016

-15 15 0 5-5 10-10

LHCb HeRSCheL

(gap)

(gap)

(gap)(gap)

(gap)

(gap)

(gap)

Single diffraction

Double diffraction

CEP elastic

CEP inelastic

CEP inelastic

Elastic scattering

Melody Ravonel Salzgeber: 29.09.2016

Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016

-15 15 0 5-5 10-10

LHCb HeRSCheL

(gap)

(gap)

(gap)(gap)

(gap)

(gap)

(gap)

Single diffraction

Double diffraction

CEP elastic

CEP inelastic

CEP inelastic

Elastic scattering

Melody Ravonel Salzgeber: 29.09.2016

Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016Melody Ravonel Salzgeber: 29.09.2016

-15 15 0 5-5 10-10

LHCb HeRSCheL

(gap)

(gap)

(gap)(gap)

(gap)

(gap)

(gap)

Single diffraction

Double diffraction

CEP elastic

CEP inelastic

CEP inelastic

Elastic scattering

pseudorapidity η

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analysis HeRSCheL - forward scintillators

separation of coherent and incoherent

)2/GeV2

Tlog(p

10− 5− 0

Eve

nts

/ 0.6

020406080

100120140160180200220 data without Herschel

data with Herschel

LHCb Preliminary = 5 TeVNNsPb-Pb

The use of the HeRSCHeL detector does remove a lot of the incoherent backgroundsAlbert Bursche UPC J/ψ 14th May 2018 13 / 14

LHCb-CONF-2018-003

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analysis HeRSCheL - forward scintillators

conclusion

LHCb has measured the cross section for coherent J/ψ production in lead-leadcollisions

We have potential to improve the precision of this measurement

We are looking forward to a larger data set in fall 2018

Thank You!

Albert Bursche UPC J/ψ 14th May 2018 14 / 14