Post on 10-Aug-2020
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
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
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
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
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
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
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
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
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
Albert Bursche UPC J/ψ 14th May 2018 5 / 14
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
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)
Albert Bursche UPC J/ψ 14th May 2018 7 / 14
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
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
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
Albert Bursche UPC J/ψ 14th May 2018 10 / 14
LHCb-CONF-2018-003
analysis HeRSCheL - forward scintillators
HeRSCHeL - forward scintillators
Albert Bursche UPC J/ψ 14th May 2018 11 / 14
analysis HeRSCheL - forward scintillators
HeRSCHeL - forward scintillators
Albert Bursche UPC J/ψ 14th May 2018 11 / 14
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
Albert Bursche UPC J/ψ 14th May 2018 12 / 14
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
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