nuclear pdfs: latest update - wlab.yale.edu · pdf filethe proposal is: pqcd is successful...

Nuclear PDFs: latest update

(and future facilities)

P. Zurita

February 16th, 2017 Wright laboratory, Yale University, CT, USA

Disclaimer

I will talk only about observables

included in PDFs and nPDFs fits,

computed with dear old pQCD.

Any other measurement can eventually

be included, just not part of the

talk :)

OutlineThe questions: what, why, how?

Where were we?

Where are we?

Where are we going?

Summary

What are PDFs?WHAT?

d�(p+ l ! l0 +X) =X

a

d�̂la!l0X ⌦ fa

d�(p+ l ! l0 +X + h) =X

a,b

d�̂la!b ⌦ fa ⌦ Dhb

d�(p+ p ! l++ l�) =X

a,b

d�̂ab!ll̄ ⌦ fa ⌦ fb

d�(p+ p ! X + h) =X

a,b,c

d�̂ab!c ⌦ fa ⌦ fb ⌦ Dhc

What are PDFs?

d�(p+ l ! l0 +X) =X

a

d�̂la!l0X ⌦ fa

d�(p+ l ! l0 +X + h) =X

a,b


d�(p+ p ! l++ l�) =X

a,b


d�(p+ p ! X + h) =X

a,b,c


hard

WHAT?

What are PDFs?

d�(p+ l ! l0 +X) =X

a

d�̂la!l0X ⌦ fa

d�(p+ l ! l0 +X + h) =X

a,b


d�(p+ p ! l++ l�) =X

a,b


d�(p+ p ! X + h) =X

a,b,c


SOFT

WHAT?

But the title reads nuclear PDFs WHAT?

But the title reads nuclear PDFs early 80’s: measurement of DIS cross-sections in e-A collisions

d

2�

eh!eX

dxdQ

2=

4⇡↵2e.m.

xQ

4

" 1� y +

y

2

2

!F2(x,Q

2)� y

2

2FL(x,Q

2)

#

WHAT?

effect in cross-section

is this a hard, soft or hard and soft effect?

WHAT?

the proposal is:

pQCD is successful don’t want to throw it away

factorization holds

change only in the soft part

WHAT?

so now

d�(A+ l ! l0 +X) =X

a

d�̂la!l0X ⌦ fAa

d�(A+ l ! l0 +X + h) =X

a,b

d�̂la!b ⌦ fAa ⌦ Dh

b

d�(A+ p ! l++ l�) =X

a,b

d�̂ab!ll̄ ⌦ fAa ⌦ fb

d�(A+ p ! X + h) =X

a,b,c

d�̂ab!c ⌦ fAa ⌦ fb ⌦ Dh

c

WHAT?

do I need these? really?

WHY?

WHY?

do I need these? really? WHY?because in QCD they are crucial for describing the perturbative regime of

WHY?


because in QCD they are crucial for describing the perturbative regime of

nuclear DIS

WHY?WHY?



nuclear DIS

WHY?

non QGP effects in p-A, d-A, A-A

WHY?



nuclear DIS

WHY?

cosmic rays


WHY?



nuclear DIS

WHY?

neutrino DIS (needed for proton PDFs)

cosmic rays


WHY?

How? All soft contributions are determined by global QCD analyses

HOW?

pick data sets


HOW?

compute the observables


pick data sets

HOW?

assumed initial shape of the nuclear/proton

PDF ratio (Rvalence, Rsea and Rgluon)

f

p/Ai (x,Q0) = f

pi (x,Q0)Ri(x,A)

A-dependent parameters

Schematic View of x Dependence of nPDFs

Most nuclear parton densities assume a similar shape, the details depend on theassumptions made and the data included in the fit procedureAmount and shape of antishadowing region depends on whether it is for valencequarks, sea quarks or gluons

0.2

0.6

1.0

1.5

10-3 10-2 10-1 1

ya

ye

xa xe

y0 shadowing

antishadowing

EMC-effect

Fermi-motion

5

HOW?

weights: amount and accuracy of the data

data sets: DIS, DY, p(d)-A, SIDIS, cross-sections, rates

theory: LO, NLO, quarks mass error treatment: correlation matrix

construct χ2

�2 =X

i

wi

d�exp

i

� d�th

i

�i

!2


pick data sets


�2 =X

i

wi

d�exp

i

� d�th

i

�i

!2

HOW?

move parameters until minimum reached

�2 =X

i

wi

d�exp

i

� d�th

i

�i

!2


pick data sets


�2 =X

i

wi

d�exp

i

� d�th

i

�i

!2

�2 =X

i

wi

d�exp

i

� d�th

i

�i

!2

construct χ2weights: amount and accuracy of

the data data sets: DIS, DY, p(d)-A, SIDIS,

cross-sections, rates theory: LO, NLO, quarks mass

error treatment: correlation matrix

HOW?

�2 =X

i

wi

d�exp

i

� d�th

i

�i

!2

all done!


pick data sets


construct χ2weights: amount and accuracy of

the data data sets: DIS, DY, p(d)-A, SIDIS,

cross-sections, rates theory: LO, NLO, quarks mass

error treatment: correlation matrix

�2 =X

i

wi

d�exp

i

� d�th

i

�i

!2

move parameters until minimum reached

HOW?

… too good to be true😞

HOW?

… too good to be true

which data sets? to which order? heavy quarks mass effects? scales? error treatment? weights? parameters? …?

😞

HOW?

nDS: de Florian, Sassot, Phys.Rev. D69 (2004)

HKN: Hirai, Kumano, Nagai, Phys.Rev. C76 (2007) —> KEK nuclear physics textbook (2015)

EPS09: Eskola, Paukkunen, Salgado, JHEP 0904 (2009)

DSSZ: de Florian, Sassot, Stratmann, PZ, Phys.Rev. D85 (2012)

nCTEQ15: Kovarik et al., Phys.Rev. D93 (2016)

LO

WHERE WERE WE?

EKS: Eskola, Kolhinen, Salgado, Eur.Phys.J. C9 (1999)

HKM: Hirai, Kumano, Miyama, Phys.Rev. D64 (2001)

NLO

EPPS16: Eskola, Paakkinen, Paukkunen, Salgado, arXiv:1612.05741

NNLO KA15: Khanpour, Tehrani, Phys.Rev. D93 (2016) no.1, 014026

to come a) A-Z: NNLO b) NNPDF: Pb nPDFs

Paukkunen, Nucl. Phys. A 926 (2014) 24WHERE WERE WE?

0.40.60.8

11.21.41.61.8

0.40.60.8

11.21.41.6

d dA

u/d

pp

0

PHENIX STAR

this fit (nFF)this fit (DSS)

d dA

u/d

pp

+

EPS 09 (DSS)nDS (DSS)

d dA

u/d

pp

-

pT [GeV]0.40.60.8

11.21.41.6

0 5 10 15

de Florian, Sassot, Stratmann,

PZ, Phys.Rev. D85 (2012)

most gluon sensitive data (62 points)

WHERE WERE WE?

Paukkunen, Nucl. Phys. A 926 (2014) 24

Outside the kinematical region probed by the experiments we have extrapolations

given by the initial shape

model dependent

not entirely reliable

WHERE WERE WE?

- High x: no constraints

- Low x: extrapolations

- No sensitivity to flavour separation

- No sensitivity to gluon density at low nor high x

in general with the data we had

WHERE WERE WE?

SET DSSZPRD85 (2012)

nCTEQ15PRD93 (2016)

KA15PRD93 (2016)

data

type

e-DIS ✔ ✔ ✔

D-Y ✔ ✔ ✔

pions ✔ ✔ ✘

ν-DIS ✔ ✘ ✘

EW ✘ ✘ ✘

jets ✘ ✘ ✘

# data points 1579 740 1479

accuracy NLO NLO NNLO

proton PDF MSTW2008 ~ CTEQ6.1 JR09

flavour separation? no valence only no

Where are we after

LHC Run I?

form the pPb white paper estimations

J.Phys. G39 (2012) 015010

WHERE ARE WE?

Before EPPS16 N. Armesto, H. Paukkunen, J.M. Penín, C. A. Salgado and P.Z., EPJ C76 (2016) no.4, 218

jets (ATLAS)

charged hadrons (ALICE, CMS) and pions (ALICE)

W boson (ALICE, CMS) and Z boson (ATLAS, CMS)

di-jets (CMS)

only the last two included in EPPS16 arXiv:1612.05741

http://www.int.washington.edu/talks/WorkShops/int_17_65W/

WHERE ARE WE?

arXiv:1612.05741

WHERE ARE WE?

Zd�(y Z

)/d�(�y Z

)

yZ

EPPS16

No nuclear e↵ects

66 GeV < M`+`� < 116 GeV

ATLAS data

Z production, pPb,

ps = 5.02TeV

d�(y Z

�0.4)/d�(�y Z

�0.4)

yZ � 0.4

EPPS16

No nuclear e↵ects

60 GeV < M`+`� < 120 GeV

|⌘`±lab| < 2.4

pT(`±) > 20 GeV

CMS data

Z production, pPb,

ps = 5.02 TeV

arXiv:1612.05741

WHERE ARE WE?

x ⇡ MZ,Wps

e

�y

Phys.Lett. B750 (2015) 565-586

W+/-

good candidate for flavour decomposition

WHERE ARE WE?

W+/-d�(y `

+

)/d�(�y `

+

)

lepton rapidity (lab frame)

EPPS16

No nuclear e↵ects

CMS data

W+

production, pPb

ps = 5.02 TeV

pT (`+

) > 25 GeV

d�(y `

�)/d�(�y `

�)

lepton rapidity (lab frame)

EPPS16

No nuclear e↵ects

pT (`�) > 25 GeV

CMS data

W�production, pPb,

ps = 5.02 TeV

arXiv:1612.05741

WHERE ARE WE?

Phys.Lett. B750 (2015) 565-586

W+/-

good candidate for flavour decomposition arXiv:1612.05741

WHERE ARE WE?

di-jets

Eur.Phys.J. C74 (2014) no.7, 2951

WHERE ARE WE?

arXiv:1612.05741

di-jets

WHERE ARE WE?

Rvalence

arXiv:1612.05741

WHERE ARE WE?

Rsea

arXiv:1612.05741

WHERE ARE WE?

arXiv:1612.05741

Rgluon

WHERE ARE WE?

SET DSSZPRD85 (2012)

nCTEQ15PRD93 (2016)

KA15PRD93 (2016)

EPPS16 arXiv:1612.05741

data

type

e-DIS ✔ ✔ ✔ ✔

D-Y ✔ ✔ ✔ ✔

pions ✔ ✔ ✘ ✔

ν-DIS ✔ ✘ ✘ ✔

EW ✘ ✘ ✘ ✔

jets ✘ ✘ ✘ ✔

# data points 1579 740 1479 1811

accuracy NLO NLO NNLO NLO

proton PDF MSTW2008 ~ CTEQ6.1 JR09 CT14NLO

flavour separation? no valence only no yes!

the new set is great, but what have we learned so far?

WHERE ARE WE?

the new set is great, but what have we learned so far?

- call for flavour separation in the nPDFs can be answered by data

- di-jets strongly depend on proton PDFs

- accurate FFs needed

WHERE ARE WE?

LHC Run II

RHIC

EIC

LHeC??

The future:

WHERE ARE WE GOING?

LHC:

- Run I: measured pp reference @5TeV,

ratios to be re-analysed, observables

not considered before could be

included

- Run II: already a pp reference @ 8TeV,

LHCb involved, new FFs to come

WHERE ARE WE GOING? TO CERN

Aschenauer et al., arXiv:1602.03922 [nucl-ex]

direct photon

WHERE ARE WE GOING? TO BNL

g + q ! q + �


direct photon

0

0.5

1

1.5

10 -4 10 -3 10 -2 10 -1 1

Rg(P

b)(x

,Q2 =1

.0 G

eV2 )

x

DSSZ before rew.

DSSZ after rew.

EPS09 before rew.

EPS09 after rew.

Rg(P

b)(x

,Q2 =1

.69

GeV

2 )

x

0

0.5

1

1.5

10 -4 10 -3 10 -2 10 -1 1


g + q ! q + �

Drell-Yan

Aschenauer et al., arXiv:1602.03922 [nucl-ex]WHERE ARE WE GOING? TO BNL

Drell-Yan


0.2

0.4

0.6

0.8

1

1.2

10 -4 10 -3 10 -2 10 -1 1

Rse

a(Pb)

(x,Q

2 =1.0

GeV

2 )

x

DSSZ before rew.

DSSZ after rew.

EPS09 before rew.

EPS09 after rew.

Rse

a(Pb)

(x,Q

2 =1.6

9 G

eV2 )

x

0.2

0.4

0.6

0.8

1

1.2

10 -4 10 -3 10 -2 10 -1 1


Great possibilities!

Accardi et al., Eur.Phys.J. A52 (2016) no.9, 268 WHERE ARE WE GOING? TO BNL? 🤞

F2 World Data (A≥Fe)CTEQ10+EPS09

1 10 102 1030

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

8.2×10-1

5.2×10-1

3.2×10-1

2.0×10-1

1.3×10-1

8.2×10-2

5.2×10-2

3.2×10-2

2.0×10-21.3×10-2

8.2×10-35.2×10-3 3.2×10-3 2.0×10-3 1.3×10-3 8.2×10-4

5.2×10-43.2×10-4

x = 2.0×10-4

F 2(x

,Q2 )

- lo

g 10(

x)

Q2 (GeV2)

∫Ldt = 10 fb-1/A

5 on 50 GeV5 on 100 GeV20 on 100 GeV

F2 in e+Au

Errors enlarged by factor 3

20 on 50,75,100 GeV5 on 50,75,100 GeV

x = 3.7×10-4

x = 6.3×10-4

x = 1.4×10-3

x = 2.6×10-3

x = 3.8×10-3

x = 5.8×10-3

x = 9.1×10-3

x = 1.6×10-2

x = 3.0×10-2

1 10 102 1030

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

F L(x

,Q2 )

- lo

g 10(

x)

Q2 (GeV2)

∫Ldt = 10 fb-1/AFL in e+Au

Accardi et al., Eur.Phys.J. A52 (2016) no.9, 268

WHERE ARE WE GOING? TO BNL? 🤞

Accardi et al., Eur.Phys.J. A52 (2016) no.9, 268

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

5.2×10-1

3.2×10-12.0×10-1

1.3×10-1

8.2×10-2

5.2×10-2

3.2×10-2

2.0×10-21.3×

10-2

8.2×1

0-3

5.2×1

0-32.

0×10

-33.

2×10

-3

1.3×

10-3

8.2×1

0-4

5.2×1

0-4

3.2×1

0-4

x = 2

.0×1

0-4

1 10 102 103

Q2 (GeV2)

F 2cc̄(x

,Q2 )

- lo

g 10(

x)/1

0

F2cc̄ in e+Au5 on 50 GeV5 on 100 GeV20 on 100 GeVCTEQ10+EPS09

∫Ldt = 10 fb-1/A0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

10-210-3

xF 2cc̄

(Sat

urat

ion

Mod

el)/F

2c c̄(E

PS09

)

Error on EIC F2cc̄ data

Q2 = 2.47 GeV2

Q2 = 4.39 GeV2

Q2 = 7.81 GeV2

Never measured for eA!


J.H. Lee, IS2016, Lisbon


Sassot, Stratmann and P.Z., Phys.Rev. D81 (2010) 054001

R⇡

A

=

⇣N

⇡(x,Q2,z)

N

e(x,Q2)

⌘

A⇣N

⇡(x,Q2,z)

N

e(x,Q2)

⌘

d


Aballeira et al., J. Phys. G 39 (2012) 075001

WHERE ARE WE GOING? TO CERN? 🤞

Armesto, Helenius and Paukkunen, PoS DIS2016 (2016) 276

WHERE ARE WE GOING? TO CERN? 🤞

several sets of nPDFs available

Summary

strange and gluon distributions

not yet well constrained by data


Summary


p-Pb @ the LHC and pA @ RHIC

crucial to study the low x region



Summary

EIC (LHeC?) to go further

Summaryseveral sets of nPDFs available

p-Pb @ the LHC and pA @ RHIC

crucial to study the low x region



nuclear effects truly universal? correlated errors? more data in DY?

high pT particle production? cross-sections instead of structure functions?

nuclear effects for deuteron? more flexible parameterizations?

higher fixed-order analyses? A-A collisions?

centrality dependence? final state nuclear effects?

...???

ongoing and to do

That’s all folks!

That’s all folks!

for now 😉

nuclear pdfs: latest update - wlab.yale.edu · pdf filethe proposal is: pqcd is successful...

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