Diffractive particle production as a probe of high-energy QCD · QCD at high...
Transcript of Diffractive particle production as a probe of high-energy QCD · QCD at high...
Diffractive particle production as a probe of high-energy QCD
Heikki Mantysaari
University of Jyvaskyla, Finland
Zimanyi school’19December 5, 2019
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 1 / 18
Why diffraction
Exclusive production of a vectormeson/dijet/diffracive system
γ + A→ V + A
γ + A→ jet1 + jet2 + A
γ + A→ MX + A
Pocket formula for VM production (2-gluon exchange), [Ryskin 1993]
dσγ∗H→VH
dt
∣∣∣∣t=0
=16π3α2
sΓee
3αemM5V
[xg(x,Q2)
]2
Diffraction is very sensitive to (small-x) gluons!Measure t (conjugate to impact parameter) ⇒ access to geometryBut PDFs are inclusive quantities, this is exclusive...
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 1 / 18
QCD at high energy: Color Glass Condensate
(DGLAP)
(BK)
CGC = QCD at high energies
x (energy) dependence:BK/JIMWLK (perturbative)
Gluon saturation at small x at scale Q2s
Non-linear effects enhanced in nucleiQ2
s ∼ A1/3
Natural framework to describe high energy scattering,which probes QCD in the non-linear regime
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 2 / 18
Deep inelastic scattering at high energy: dipole picture
Optical theorem:σγ
∗p ∼ dipole amplitude σγ∗p→Vp ∼ |dipole amplitude|2
Univesal dipole amplitude
Same universal QCD evolved dipole amplitude N
N ∼ gluon
Structure function ∼ gluon
Diffractive cross sections ∼ gluon2 ⇒ saturation effects especially in nuclei!
Perturbative x evolution (BK, JIMWLK), non-perturbative initial condition: fit HERA F2
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 3 / 18
Dipole model fits to DIS (γ∗p) data
Successful fits to precise σr data at small x (LO, NLO in preparation Beuf, Lappi, Hanninen, Mantysaari )
Initial condition for perturbative small-x evolution of the dipoleDiffraction more complicated, perturbative geometry evolution → Coulomb tailsAlbacete et al 2009, Albacete et al 2010, Berger, Stasto, 2012, Lappi, Mantysaari 2013, Mantysaari, Schenke 2018, Bendova et al 2019
Parametrized x dependence and geometry (e.g. IPsat)Kowalski, Teaney 2003, Rezaeian et al, 2012, Mantysaari, Zurita 2018,...0.4
0.6
0.8
1.0
1.2
1.4
1.6
�r
Q2 = 2.7 GeV2
IPsat
Q2 = 18 GeV2 Q2 = 120 GeV2
10�4 10�3 10�2
x
0.4
0.6
0.8
1.0
1.2
1.4
1.6
�r
Q2 = 2.7 GeV2
10�4 10�3 10�2
x
Q2 = 18 GeV2
10�4 10�3 10�2
x
Q2 = 120 GeV2
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 4 / 18
Probe of the geometry: exclusive J/Ψ production
High energy factorization:
1 γ∗ → qq: Ψγ(r ,Q2, z)
2 qq dipole scatters elasticallyAmplitude N
3 qq → J/Ψ: ΨV (r ,Q2, z)
Diffractive scattering amplitude
Aγ∗p→Vp ∼∫
d2bdzd2rΨγ∗ΨV (r , z ,Q2)e−ib·∆N(r , x ,b)
Impact parameter is the Fourier conjugate of the momentum transfer→ Access to the spatial structure
Total F2: forward elastic scattering amplitude (∆ = 0) for V = γ
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 5 / 18
Average over target configurations
Coherent diffraction:Target remains in the same quantum stateProbes average density
dσγ∗A→VA
dt∼ |〈Aγ∗A→VA〉|2
Incoherent/target dissociation:Total diffractive − coherent cross sectionTarget breaks up
dσγ∗A→VA∗
dt∼ 〈|Aγ∗A→VA|2〉 − |〈Aγ∗A→VA〉|2
Variance, measures the amount of fluctuations (“lumpiness”)!
dσ/d
t
|t|
Coherent/Elastic
Incoherent/Breakup
t1 t2 t3 t4
Good, Walker, PRD 120, 1960Miettinen, Pumplin, PRD 18, 1978Kovchegov, McLerran, PRD 60, 1999Kovner, Wiedemann, PRD 64, 2001
〈 〉: average over target configurations [N(r, x, b)]
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 6 / 18
Average over target configurations
Coherent diffraction:Target remains in the same quantum stateProbes average density
dσγ∗A→VA
dt∼ |〈Aγ∗A→VA〉|2
Incoherent/target dissociation:Total diffractive − coherent cross sectionTarget breaks up
dσγ∗A→VA∗
dt∼ 〈|Aγ∗A→VA|2〉 − |〈Aγ∗A→VA〉|2
Variance, measures the amount of fluctuations (“lumpiness”)!
dσ/d
t
|t|
Coherent/Elastic
Incoherent/Breakup
t1 t2 t3 t4
Good, Walker, PRD 120, 1960Miettinen, Pumplin, PRD 18, 1978Kovchegov, McLerran, PRD 60, 1999Kovner, Wiedemann, PRD 64, 2001
〈 〉: average over target configurations [N(r, x, b)]
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 6 / 18
Beyond the round proton
Recall: coherent cross section ∼ average, incoherent ∼ variance⇒ need event-by-event fluctuating N(r,b)
Constituent quark inspired picture
Sample hot spot substructure, geometry and density fluctuation
Use constraints from coherent and incoherent cross sections(average profile and amount of fluctuations)Mantysaari, Schenke 2016, 2017, Cepila, Contreras, Takaki 2017, 2018
Tproton(b) =3∑
i=1
Tq(b− bi ) Tq(b) ∼ e−b2/(2Bq)
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 7 / 18
Proton structure from HERA data on γ + p → J/Ψ + p
Sample color charges, solve Yang-Mills equations ⇒ Wilson lines ⇒ dipole amplitude NH.M., B. Schenke, PRL 117 (2016), 052301, PRD94 (2016), 034042
0.0 0.5 1.0 1.5 2.0
|t| [GeV2]
10−1
100
101
102
103
dσ/dt
[nb/G
eV2]
Incoherent
Coherent
Round protonGeometry and Qs fluctuationsH1 coherentH1 incoherent
−1
0
1
y[f
m]
−1 0 1x[fm]
−1
0
1
y[f
m]
−1 0 1x[fm]
0.0
0.2
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1.0
1.2
HERA data (at x ≈ 10−3) preferes large fluctuations
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 8 / 18
Perturbative JIMWLK energy evolution from CGC
Size fixed at W = 30GeV, αs and ΛQCD fixed by charm-F2
102 103
W [GeV]
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
BG
[GeV−
2]
Fixed αsRunning αsIPsat
H1 (2005)H1 (2013)ZEUS
Fit range 0.1 < |t| < 0.6 GeV2
Running αs : faster evolution at long distance scales. rRMS ≈√
2BG
Dashed: no geometry evolution (only density). H.M, B. Schenke, 1806.06783
x = 10−2
x = 10−4
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 9 / 18
Energy evolution from CGC → smoother proton at small x
Fluctuations fixed at W = 75 Gev, then JIMWLK evolution H.M, B. Schenke, 1806.06783
102 103
W [GeV]
0.4
0.6
0.8
1.0
inco
her
ent/
coh
eren
t
MV + JIMWLK+ UV damping at x0
IPsatH1
Evolution parameters constrained by the charm-F2 dataSolid and dashed: JIMWLK with different initial conditionsDotted: no geometry evolution
W = 75 GeV:
W = 680 GeVH.M, B. Schenke, 1806.06783
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 10 / 18
Exclusive J/Ψ production at small x at the LHC
Ultraperipheral p + A:Photon flux ∼ Z 2
γ + p dominatesE
Pb
p
Low energy γ − A: coherent and incoherent visible ALICE: 1406.7819
Dimuon pT
Larger COM energies:incoherent → 0 (?)⇒ smoother proton?ALICE:1809.03235
x ∼ 10−2 → 10−5
Energy dependence of exclusive J/y photoproduction ... ALICE Collaboration
)c (GeV/TpDielectron
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
)cD
iele
ctro
n co
unts
/ (1
00 M
eV/
0
10
20
30
40
50
60
= 5.02 TeVNNsALICE p-Pb -e+ e→ψJ/
< 0.8y-0.8 < 2c < 3.2 GeV/-e+em2.9 <
SumψExclusive J/
Non-exclusive bkg.-e+ e→ γγ
+Pbγ
)c (GeV/TpDimuon
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
)cD
imuo
n co
unts
/ (8
0 M
eV/
0
20
40
60
80
100 = 5.02 TeVNNsALICE p-Pb -µ+µ → ψJ/
< 0.8y-0.8 < 2c < 3.2 GeV/-µ+µm3.0 <
SumψExclusive J/
Non-exclusive bkg.-µ+µ → γγ
+Pbγ
)c (GeV/TpDimuon
0 0.5 1 1.5 2 2.5
)cD
imuo
n co
unts
/ (1
50 M
eV/
0
10
20
30
40
50
60
70
80 = 5.02 TeVNNsALICE p-Pb -µ+µ → ψJ/
< 2.7y1.2 < 2c < 3.2 GeV/-µ+µm2.9 <
SumψExclusive J/
Non-exclusive bkg.-µ+µ → γγ
)c (GeV/TpDimuon
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
)cD
imuo
n co
unts
/ (2
00 M
eV/
0
5
10
15
20
25
30
35
40 = 5.02 TeVNNsALICE Pb-p -µ+µ → ψJ/
< -1.2y-2.5 < 2c < 3.2 GeV/-µ+µm2.9 <
SumψExclusive J/
Non-exclusive bkg.-µ+µ → γγ
Figure 2: Transverse momentum distributions of dileptons around the J/y mass for the dielectron (upper left)and dimuon (upper right) samples for the central analysis and dimuon samples for the semi-forward (lower left)and semi-backward (lower right) analyses. In all cases the data are represented by points with error bars. Theblue, magenta (dash) and green (dash-dot-dot) lines correspond to Monte Carlo templates for J/y coming fromexclusive photoproduction off protons or off lead and continuous dilepton production respectively. The red (dash-dot) line is a template for dissociative and hadronic background obtained from data. The solid black line is the sumof all contributions.
The systematic uncertainty on the yield was obtained by varying the range of fit to the transverse momen-tum template, the width of the binning and the selections and smoothing algorithms used to determinethe non-exclusive template. (See section 3.3.) Furthermore, the value of the b parameter used in theproduction of the exclusive J/y template was varied, taking into account the uncertainties reported byH1 [10]. The uncertainty varies from 1.9% to 3.6%. (See “signal extraction” in Table 2.)
The polarization of the J/y coming from y(2S) feed-down is not known. The uncertainty on the amountof feed-down has been estimated by assuming that the J/y was either not polarised or that it was fullytransversely or fully longitudinally polarised. This uncertainty is asymmetric and varies from +1.0% to�1.4%. (See “feed-down” in Table 2.)
10
Energy dependence of exclusive J/y photoproduction ... ALICE Collaboration
)c (GeV/TpDielectron
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
)cD
iele
ctro
n co
unts
/ (1
00 M
eV/
0
10
20
30
40
50
60
= 5.02 TeVNNsALICE p-Pb -e+ e→ψJ/
< 0.8y-0.8 < 2c < 3.2 GeV/-e+em2.9 <
SumψExclusive J/
Non-exclusive bkg.-e+ e→ γγ
+Pbγ
)c (GeV/TpDimuon
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
)cD
imuo
n co
unts
/ (8
0 M
eV/
0
20
40
60
80
100 = 5.02 TeVNNsALICE p-Pb -µ+µ → ψJ/
< 0.8y-0.8 < 2c < 3.2 GeV/-µ+µm3.0 <
SumψExclusive J/
Non-exclusive bkg.-µ+µ → γγ
+Pbγ
)c (GeV/TpDimuon
0 0.5 1 1.5 2 2.5
)cD
imuo
n co
unts
/ (1
50 M
eV/
0
10
20
30
40
50
60
70
80 = 5.02 TeVNNsALICE p-Pb -µ+µ → ψJ/
< 2.7y1.2 < 2c < 3.2 GeV/-µ+µm2.9 <
SumψExclusive J/
Non-exclusive bkg.-µ+µ → γγ
)c (GeV/TpDimuon
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
)cD
imuo
n co
unts
/ (2
00 M
eV/
0
5
10
15
20
25
30
35
40 = 5.02 TeVNNsALICE Pb-p -µ+µ → ψJ/
< -1.2y-2.5 < 2c < 3.2 GeV/-µ+µm2.9 <
SumψExclusive J/
Non-exclusive bkg.-µ+µ → γγ
Figure 2: Transverse momentum distributions of dileptons around the J/y mass for the dielectron (upper left)and dimuon (upper right) samples for the central analysis and dimuon samples for the semi-forward (lower left)and semi-backward (lower right) analyses. In all cases the data are represented by points with error bars. Theblue, magenta (dash) and green (dash-dot-dot) lines correspond to Monte Carlo templates for J/y coming fromexclusive photoproduction off protons or off lead and continuous dilepton production respectively. The red (dash-dot) line is a template for dissociative and hadronic background obtained from data. The solid black line is the sumof all contributions.
The systematic uncertainty on the yield was obtained by varying the range of fit to the transverse momen-tum template, the width of the binning and the selections and smoothing algorithms used to determinethe non-exclusive template. (See section 3.3.) Furthermore, the value of the b parameter used in theproduction of the exclusive J/y template was varied, taking into account the uncertainties reported byH1 [10]. The uncertainty varies from 1.9% to 3.6%. (See “signal extraction” in Table 2.)
The polarization of the J/y coming from y(2S) feed-down is not known. The uncertainty on the amountof feed-down has been estimated by assuming that the J/y was either not polarised or that it was fullytransversely or fully longitudinally polarised. This uncertainty is asymmetric and varies from +1.0% to�1.4%. (See “feed-down” in Table 2.)
10
Medium E Large EHeikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 11 / 18
Searching for saturation effects
Saturation models (“sat”) and linearized models (“nonsat”), describe inclusive HERA dataSimilar predictions for diffractive J/Ψ production.
0.4
0.6
0.8
1.0
1.2
1.4
1.6
�r
Q2 = 2.7 GeV2Q2 = 2.7 GeV2
IPsatIPnonsat
Q2 = 18 GeV2Q2 = 18 GeV2 Q2 = 120 GeV2Q2 = 120 GeV2
10�4 10�3 10�2
x
0.80.91.01.11.21.31.41.5
�r
Q2 = 120 GeV2Q2 = 120 GeV2
10�4 10�3 10�2
x
Q2 = 200 GeV2Q2 = 200 GeV2
10�4 10�3 10�2
x
Q2 = 120 GeV2Q2 = 120 GeV2
102 103 104
W [GeV]
102
103
σ[n
b]
IPsatIPnonsatH1 (2005)
H1 (2013)ZEUSALICE (2014)
γ + p→ J/Ψ + p,Q2 = 0 GeV2
IPsat and IPnonsat fitted to the same σr dataH.M, P. Zurita, 1804.05311
Need higher gluon densities than accessible in γ + p(?)Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 12 / 18
High gluon densities in nuclei
Enhance saturation effects:Q2
s,A ∼ A1/3x−λ
(larger A is cheaper than smaller x)Already data from UPCs,momentum fraction x = MV e
y/√s
E
Z e1
Z e2
y0.5− 0 0.5 1 1.5 2 2.5 3 3.5
/ dy
[mb]
coh
σd
0
1
2
3
4
5
6
7
8
9CMS dataALICE dataImpulse approximationLeading twist approximation
(2.76 TeV)-1bµ 159 ψ Pb+Pb+J/→Pb+Pb
CMS
CMS, 1605.06966Clear nuclear effects: impulse approximation is scaled γ + p
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 13 / 18
Coherent diffraction, model comparison
y
4 2 0 2 4
/dy (
mb
)σ
d
0
1
2
3
4
5
6
7
8
RSZLTA
STARLIGHTGM
ABEPS09
ABMSTW08
ABEPS08
ABHKN07
CSS
LMfIPSat
ψALICE Coherent J/
Reflected
a) = 2.76 TeVNN
s ψ Pb+Pb+J/→Pb+Pb
ALICE, 1305.1467
Shadowing/saturation needed
LM-fIPsat (CGC)
AB-PS09 (nPDF)
Linear models fail
AB-MSTW08 (proton PDF)
CGC: inclusive and diffractive observables from the same framework (depend on dipole N)Exclusive data difficult to include in nPDF fits (PDFs are inclusive)
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 14 / 18
Extract nuclear geometry
Full EIC simulation with expected uncertainties in γ + A→ J/Ψ + A
|t | (GeV2) |t | (GeV2)0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18
J/ψ φ
|η(edecay)| < 4p(edecay) > 1 GeV/cδt/t = 5%
∫Ldt = 10/A fb-11 < Q2 < 10 GeV2, x < 0.01
∫Ldt = 10/A fb-11 < Q2 < 10 GeV2, x < 0.01
|η(Kdecay)| < 4p(Kdecay) > 1 GeV/cδt/t = 5%
104
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102
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10-2
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102
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10-2
coherent - no saturationincoherent - no saturationcoherent - saturation (bSat)incoherent - saturation (bSat)
coherent - no saturationincoherent - no saturationcoherent - saturation (bSat)incoherent - saturation (bSat)
(a) (b)
dσ(e
Au →
e' A
u' J/ψ
) /dt (
nb/G
eV2 )
dσ(e
Au →
e' A
u' φ)
/dt (
nb/G
eV2 )
Coherent J/Ψ spectra ⇒ FT⇒ Density profile
-10 -5 1050 -10 -5 1050
-10 -5 1050-10 -5 1050
0
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φ bNonSatWoods-Saxon
F(b)
/ ∫F(b
) db
F(b)
/ ∫F(b
) db
F(b)
/ ∫F(b
) db
F(b)
/ ∫F(b
) db
b (fm)
b (fm)b (fm)
b (fm)
J/ψ bNonSatWoods-Saxon
φ bSatWoods-Saxon
J/ψ bSatWoods-Saxon
(a) (b)
(c) (d)Extract transverse density profile of small-x gluons T. Toll, T. Ullrich, 1211.3048
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 15 / 18
Fluctuations at different length scales
Small |t| . 0.2GeV2: long length scale, fluctuating nucleon positionsLarge |t| & 0.2GeV2: short length scale, fluctuating nucleon substructure
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
|t| [GeV2]
10−2
10−1
100
101
102
103
dσ/dtdy
[mb/G
eV2]
Geometric and Qs fluctuations in the nucleonsNo subnucleon fluctuations
Pb + Pb→ J/Ψ + Pb + Pb,√s = 5.02 TeV, y = 0
−3 −2 −1 0 1 2 3
y
0.1
0.2
0.3
0.4
0.5
0.6
0.7
inco
her
ent/
coh
eren
t
Geometric and Qs fluctuationsNo subnucleon fluctuationsALICE
Pb + Pb→ J/Ψ + Pb + Pb,√sNN = 2760 GeV
Subnucleon fluctuations preferred by the ALICE dataSome model uncertainties cancel in ratios (e.g. J/Ψ wave function)! H.M, B. Schenke, 1703.09256
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 16 / 18
More differential imaging: diffractive dijets
Two transverse momenta (sum and difference) ⇒ more detailed probe
Cross section modulation ∼ Wigner distribution Hatta, et al, 1601.01585
Dipole-proton scattering depends on orientation⇒ dijet anisotropies
dN ∼ 1 + 2v2 cos(2θ(P,∆))
r
Altinoluk et al, 1511.07452
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0 1 2 3 4 5 6θ(r, b)
0.90
0.95
1.00
1.05
1.10
1.15
N(r,b,y
)/v 0
CGC, |r|= 0.35 fm, |b|= 0.35 fm
y= 0.0, v0 = 0.10, v2 = 2.87%y= 1.5, v0 = 0.15, v2 = 1.89%y= 3.0, v0 = 0.21, v2 = 1.20%
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0 2.0e-03 4.0e-03 6.0e-03
150 100 60
v 2 [%
]
average xP
m~
=0.4, m=0.2, αs =0.21m~
=0.4,no JIMWLK evolution
Dipole size r-impact parameter b angular dependence from CGC.At small x larger proton, smaller density gradients, small v2 H.M, N. Mueller, B. Schenke, 1902.05087
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 17 / 18
Conclusions
Color Glass Condensate: an effective theory of QCD, same framework to describeinclusive and diffractive processes and predict energy evolution
Exclusive particle production is a powerful probe of high energy QCD
Probe ∼ squared gluon distributionAccess to geometry
Two classes of diffractive events
Coherent ∼ average shapeIncoherent ∼ event-by-event fluctuations
HERA J/Ψ data prefers large proton shape fluctuations
Fluctuating protons in p+A hydro: good description of the LHC data (backup)
γA scattering at the LHC points towards significant saturation effects
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 18 / 18
BACKUPS
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 19 / 18
Implications on heavy ion phenomenology: p+A
Hydro + fluctuations from HERA J/Ψ data: success
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Fluctuations
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 20 / 18
Implications on heavy ion phenomenology: p+A
Hydro + fluctuations from HERA J/Ψ data: success
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0.0
1.0
2.0
3.0
4.0
Rout (
fm)
0.0
1.0
2.0
3.0
4.0
Rsi
de (f
m)
0-20% pPb @ 5.02 TeV
0.0 0.2 0.4 0.6 0.8kT (GeV)
0.0
1.0
2.0
3.0
4.0
5.0
Rlo
ng (f
m)
decays onlyfull UrQMD
0.0 0.2 0.4 0.6 0.8kT (GeV)
0.50.60.70.80.91.01.1
Rou
t/R
side
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 21 / 18
Fluctuating protons in pA collisions
Hydro calculations with proton fluctuations from HERA
Hydro numbers
τ0 = 0.4 fm
Tfo = 155 MeV
Shear and bulk viscosity
Initial πµν
η/s = 0.2��
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Large v2 and v3 at largest centrality bins reproduced well.H.M, B. Schenke, C. Shen, P. Tribedy, 1705.03177
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 22 / 18
Large nuclear suppression in vector meson production
100 101 102 103
Q2 [GeV2]
0.0
0.2
0.4
0.6
0.8
1.0
σγ∗ A→VA/(
1 2A
4/3σγ∗ p→Vp)
IPsat J/Ψ IPsat φ IPsat ρ IPnonsat
W = 100, 1000 GeV
H.M, P. Zurita, 1804.05311
Especially for heavy mesons expect large nuclear effectsNo suppression with linear IPnonsat parametrizationQ2 and A scan at the EIC!
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 23 / 18
Inclusive diffraction
Higher Fock states are suppressed in the black disk limit
√s =
90
GeV
x IP =
0.0
1
√s =
40
GeV
x IP =
0.0
1
√s =
90
GeV
x IP =
0.0
01
qqg(F
AD−
A F pD
) / (A
FpD
)
Mx2 (GeV2)
001011
1.0
0.5
0
-0.5
-1.0
Q2 = 5 GeV2
xIP = 0.01xIP = 0.001
E. Aschenauer et al, 1708.01527, based on Kowalski,Lappi, Marquet,Venugopalan 0805.4071
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 24 / 18
Ultraperipheral collision as a deep inelastic scattering
b & 2RA: strong interactions are suppressed
E
Z e1
Z e2
J. Nystrand et al, nucl-ex/0502005
1 Nucleus creates a (real) photon flux n(ω)
2 Photon-nucleus scattering
σAA→AA+V ∼ n(ω)σγA→VA(ω)
Interesting QCD part: high-energy γ-nucleus or γ-proton scattering.
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 25 / 18
Dipole amplitude from IP-Glasma
Obtain saturation scale Qs(xT ) from IPsat (with fluctuations)
MV-model: Sample color charges, density ∼ Qs(xT )
Solve Yang-Mills equations to obtain the Wilson lines
V (xT ) = P exp
(−ig
∫dx−
ρ(x−, xT )
∇2 + m2
)Dipole amplitude: N(xT , yT ) = 1− TrV (xT )V †(yT )/Nc
Fix parameters Bqc ,Bq and m with HERA data
Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 26 / 18
Lumpiness matters, not details of the density profile
3 valence quarks that are connected by ”color flux tubes” (Gaussian density profile, width Bq).Also good description of the data
0.0 0.5 1.0 1.5 2.0 2.5
|t| [GeV2]
10−1
100
101
102
103
dσ/dt
[nb/G
eV2]
IPsat
Strigyn proton H1CoherentIncoherent
H.M, B. Schenke, PRD94 034042
Example density profiles
−1
0
1
y[f
m]
−1 0 1x[fm]
−1
0
1
y[f
m]
−1 0 1x[fm]
0.00
0.05
0.10
0.15
Flux tubes implementation following results from hep-lat/0606016, used also e.g. in 1307.5911Heikki Mantysaari (JYU) Diffraction and CGC Dec 5, 2019 27 / 18