qcd at the€¦ · qcd at the lhec. i. introduction. 2. the large hadron electron collider. 3....

��eQCD at the

Large HadronElectron Collider

at CERNNéstor Armesto

Departamento de Física de Partículas and IGFAEUniversidade de Santiago de Compostela

[email protected]

for the LHeC Study group, http://cern.ch/lhec 1

International Spring School of the GDR PH-QCDQCD prospects for future ep and eA colliders

Laboratoire de Physique Théorique, Orsay, June 7th 2012

mailto:[email protected]

mailto:[email protected]

http://cern.ch/lhec

http://cern.ch/lhec

Contents:

QCD at the LHeC.

I. Introduction.

2. The Large Hadron Electron Collider.

3. Precision QCD:● Parton densities.● Coupling constant.● Heavy flavors.● Jets.● Photoproduction.

4. Small x and eA:● Inclusive measurements and small-x glue.● Inclusive diffraction.● Exclusive diffraction.● Final states.

5. Summary and outlook.

2

CDR to appear within one week;cern.ch/lhec;

LHeC workshop 14-15/6/2012

Related seminar byF. Sabatié on the EIC.

http://cern.ch/lhec

http://cern.ch/lhec

https://indico.cern.ch/conferenceDisplay.py?ovw=True&confId=183282


Motivation:

3

● Complementarity of the three kind of collisions for our understanding of the interaction of matter:

QCD at the LHeC: 1. Introduction.

Messages from HERA:

4

● Very good description of F2(c,b) (FL?)within DGLAP, steep gluon in 1/x.

● Large fraction of diffraction σdiff/σtot∼10%(Cooper-Sarkar,

1206.0984).


Motivation:

5

● HERA: successful but unfinished QCD program - eA, eD, high and small x, new concepts (TMDs,...), instantons, odderon,...

Preliminary; LH

eC D

esign Study Report, C

ERN

2012


Motivation:

5

● HERA: successful but unfinished QCD program - eA, eD, high and small x, new concepts (TMDs,...), instantons, odderon,...

Preliminary; LH

eC D


ERN

2012

LHC starts to be sensitiveto differences in pdfs!!!

|Z

|y0 0.5 1 1.5 2 2.5 3 3.5

Theo

ry/D

ata

0.91

1.1

| [pb

]Z

/d|y

d

20

40

60

80

100

120

140

160

= 7 TeV)sData 2010 (

MSTW08

HERAPDF1.5

ABKM09

JR09

-1 L dt = 33-36 pb-l+ lZ

Uncorr. uncertainty

Total uncertainty

ATLAS


6

Global fits:


nPDFs (I):

Eskola

7QCD at the LHeC: 1. Introduction.

nPDFs (I):

Eskola

7

● Lack of experimental data makes the small-x region unconstrained ⇒

uncertainties on observables.

Salgado

EPS09

‘LHC without HERA’QCD at the LHeC: 1. Introduction.

nPDFs (II):

8

Yellow Report on Hard Probes, 2004

● Lack of data ⇒ models give vastly different

results for the nuclear glues at small scales and x: problem for benchmarking in HIC.

● Available DGLAP analysis at NLO show large uncertainties at small scales and x.● eA colliders not available before ∼ 2020: EIC,LHeC?

-610 -510 -410 -310 -210 -110 10

0.2

0.4

0.6

0.8

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1.4

1.6

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)2(x,1.69 GeVvu

PbR

EPS09nDSHKN07

DSSZFGS10

)2=4 GeV2(Q

-610 -510 -410 -310 -210 -110 10

0.2

0.4

0.6

0.8

1

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1.4

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)2(x,1.69 GeVuPbR

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0.2

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x

)2(x,100 GeVuPbR

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0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

x

)2(x,100 GeVgPbR

NLO analysis


nPDFs (II):

8

Yellow Report on Hard Probes, 2004

● Lack of data ⇒ models give vastly different

results for the nuclear glues at small scales and x: problem for benchmarking in HIC.

● Available DGLAP analysis at NLO show large uncertainties at small scales and x.● eA colliders not available before ∼ 2020: EIC,LHeC?

-610 -510 -410 -310 -210 -110 10

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

x

)2(x,1.69 GeVvu

PbR

EPS09nDSHKN07

DSSZFGS10

)2=4 GeV2(Q

-610 -510 -410 -310 -210 -110 10

0.2

0.4

0.6

0.8

1

1.2

1.4

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x

)2(x,1.69 GeVuPbR

-610 -510 -410 -310 -210 -110 10

0.2

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1.2

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)2(x,1.69 GeVgPbR

-610 -510 -410 -310 -210 -110 10

0.2

0.4

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0.8

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1.2

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1.6

x

)2(x,100 GeVvu

PbR

EPS09nDSHKN07

DSSZFGS10

-610 -510 -410 -310 -210 -110 10

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

x

)2(x,100 GeVuPbR

-610 -510 -410 -310 -210 -110 10

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

x

)2(x,100 GeVgPbR

NLO analysis

Inclusive J/ψQCD at the LHeC: 1. Introduction.

9

Our aims: understanding

● The implications of unitarity in a QFT.

● The behavior of QCD at large energies.

● The hadron wave function at small x.

● The initial conditions for the creation of a dense medium in heavy-ion collisions.

Origin in the early 80’s: GLR, Mueller et al, McLerran-Venugopalan.

xGA(x,Q2s)

πR2AQ2

s

∼ 1 =⇒ Q2s ∝ A1/3x∼−0.3

The ‘QCD phase’ diagram:


9

Our aims: understanding

● The implications of unitarity in a QFT.

● The behavior of QCD at large energies.

● The hadron wave function at small x.

● The initial conditions for the creation of a dense medium in heavy-ion collisions.

Origin in the early 80’s: GLR, Mueller et al, McLerran-Venugopalan.

xGA(x,Q2s)

πR2AQ2

s

∼ 1 =⇒ Q2s ∝ A1/3x∼−0.3

The ‘QCD phase’ diagram:


Questions:

● Theory: can the dense regime be described using pQCD techniques? Or non-perturbative - Regge, AdS/QCD,...?

● Phenomenology: where in this plane do present experimental data lie?

Saturation ideas: CGC

10

Hadron wave function


Saturation ideas: CGC

10

Hadron wave function

Source (frozen)

Classical,Aμ∝1/αs

O(αs)


DGLAP

BFKL

BK/JIMWLK

DILUTEREGION

DENSEREGION

saturat

ion scale

Q s(x)

ln Q

ln 1

/x

ln QCD

non-

pert

urba

tive

regi

on

DILUTEREGION

DENSEREGION

ln Aln

1/x

eA

ep

[fixed Q]

Status of small-x physics:● Three pQCD-based alternatives to describe small-x ep and eA data:→ DGLAP evolution (fixed order PT).→ Resummation schemes.→ CGC (dipole models and rcBK).Differences lie at moderate Q2(>Λ2QCD) and small x. Hints of deviations from NLO DGLAP at small x (Caola et al’09, Albacete et al’12).

● Unitarity (non-linear effects): where?

11

Two-pronged approach: ↓ x / ↑ A. eA: test/enhance density effects.


Contents:

QCD at the LHeC.

I. Introduction.





12



http://cern.ch/lhec

http://cern.ch/lhec



Project:

13

●LHeC@CERN → ep/eA experiment using p/A from the LHC:Ep=7 TeV, EA=(Z/A)Ep=2.75 TeV/nucleon for Pb.● New e+/e- accelerator: Ecm∼1-2 TeV/nucleon (Ee=50-150 GeV).● Requirements:* Luminosity∼1033 cm-2s-1. * Acceptance: 1-179 degrees(low-x ep/eA).* Tracking to 0.1 mrad.* EMCAL calibration to 0.l %.* HCAL calibration to 0.5 %.* Luminosity determination to 1 %.* Compatible with LHCoperation.

x-610 -510 -410 -310 -210 -110

)2 (G

eV2

Q

-110

1

10

210

310

410

510

610 )2(x,Q2,Anuclear DIS - F

Proposed facilities:

LHeCFixed-target data:

NMC

E772

E139

E665

EMC

(Pb, b=0 fm)2sQ

perturbative

non-perturbative

(70 GeV - 2.5 TeV)e-Pb (LHeC)

QCD at the LHeC: 2. The Large Hadron Electron Collider.

Project:

13

●LHeC@CERN → ep/eA experiment using p/A from the LHC:Ep=7 TeV, EA=(Z/A)Ep=2.75 TeV/nucleon for Pb.● New e+/e- accelerator: Ecm∼1-2 TeV/nucleon (Ee=50-150 GeV).● Requirements:* Luminosity∼1033 cm-2s-1. * Acceptance: 1-179 degrees(low-x ep/eA).* Tracking to 0.1 mrad.* EMCAL calibration to 0.l %.* HCAL calibration to 0.5 %.* Luminosity determination to 1 %.* Compatible with LHCoperation.

x-610 -510 -410 -310 -210 -110

)2 (G

eV2

Q

-110

1

10

210

310

410

510




NMC

E772

E139

E665

EMC

(Pb, b=0 fm)2sQ

perturbative

non-perturbative


Requirements LHeC HERA How?

high lumi for high x and Q2 10^33 1-5×1031

large acceptance 1-179 deg. 7-177 deg. kinematic coverage

tracking 0.1 mrad 0.2-1 mrad modern Si

EMcal 0.1 ℅ 0.2-0.5 ℅ kinematic reconstruction

Hcal 0.5 ℅ 1 ℅ tracking + calo e/h

accurate lumi/pol 0.5 ℅ 1 ℅ demanding


!"#$%&$'()*'+(),-'.-/'!"#$%&$'

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Physics goals:

14

● Proton structure to a few 10-20 m: Q2 lever arm.

● Precision QCD/EW physics.

● High-mass frontier (leptoquarks, excited fermions, contact interactions).

● Unambiguous access, in ep and eA, to a qualitatively novel regime of matter predicted by QCD.

● Substructure/parton dynamics inside nuclei with strong implications on QGP search.


Power constraintsand designconsiderations:

15QCD at the LHeC: 2. The Large Hadron Electron Collider.

Machine: Ring-Ring option

16

BYPASS

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2


Machine: Ring-Ring option

16

BYPASS

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2

eD: LeN=ALeA>∼1031 cm-2s-1.


Machine: Linac-Ring option

17

Prel

imin

ary;

Boga

cz@

DIS

11; L

HeC

D

esig

n St

udy

Rep

ort,

CER

N 2

012

500 MeV

HE LR, 140 GeV

HE LR, ER, 140 GeV


Machine: Linac-Ring option

17

Prel

imin

ary;

Boga

cz@

DIS

11; L

HeC

D

esig

n St

udy

Rep

ort,

CER

N 2

012

500 MeV

HE LR, 140 GeV

HE LR, ER, 140 GeV

eD: LeN=ALeA>∼3×1031 cm-2s-1.Large L for e+ challenging.


e

RR, high acceptance

p

The detector: low-x/eA setup

18

Prel

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ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2


e

RR, high acceptance

p


18

Prel

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ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2

pe

LR


e

RR, high acceptance

p


18

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2

pe

LR● Other detector options: low acceptance (8o-172o), solenoid outside, also considered.● Plus luminosity detector, electron tagging, polarimeter, ZDC and leading proton detector.


Ax

-510 -410

-310 -210 -110 1

)2

(G

eV

2;

Q2 T

; E

2 Tm

1

10

210

310

410

510

610Jets

Photons

|<0.9!Hadrons |

|<0.9!D’s |

|<-2.5!’s from B’s -4<|!

pA Ap

(x)2

satQ

Present

DIS+DY

data

ALICE expected reach in 1 yr. pA(Ap) collisions

Kinematics:

19Ax

-510 -410

-310 -210 -110 1

)2

(G

eV

2Q

1

10

210

310

410

510

610

|<5!Jets |

|<3!Photons |

|<2.5!Hadrons |

(x)2

satQ

Present

DIS+DY

data

CMS expected reach in 1 yr. pA(Ap) collisions

Salgado

● ep: access to the perturbative region below x ∼ a few 10-5.● eA: new realm.● No small-x physics without ∼ 1 degree acceptance.

Salgado

Black: 920+30 Green: 100+20

Q2sat,GBW

2081/3Q2sat,GBW


Ax

-510 -410

-310 -210 -110 1

)2

(G

eV

2;

Q2 T

; E

2 Tm

1

10

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410

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Photons

|<0.9!Hadrons |

|<0.9!D’s |

|<-2.5!’s from B’s -4<|!

pA Ap

(x)2

satQ

Present

DIS+DY

data

ALICE expected reach in 1 yr. pA(Ap) collisions

Kinematics:

19Ax

-510 -410

-310 -210 -110 1

)2

(G

eV

2Q

1

10

210

310

410

510

610

|<5!Jets |

|<3!Photons |

|<2.5!Hadrons |

(x)2

satQ

Present

DIS+DY

data

CMS expected reach in 1 yr. pA(Ap) collisions

Salgado

● ep: access to the perturbative region below x ∼ a few 10-5.● eA: new realm.● No small-x physics without ∼ 1 degree acceptance.

Salgado

Black: 920+30 Green: 100+20

Q2sat,GBW

2081/3Q2sat,GBW

Preliminary; LHeC Design Study Report, CERN 2012


LHeC scenarios:

20

● For FL: 10, 25, 50 + 2750 (7000); Q2≤sx; Lumi=5,10,100 pb-1 respectively; charm and beauty: same efficiencies in ep and eA.

10-310-410-4

I 50 3.5 Ca 5⋅10-4 ? 5⋅10-3 ? ? eCa

For F2

Preliminary; LH

eC D


ERN

2012


Kinematics: LHC vs. LHeC

21

Salgado

d’Enterria(Ee=140GeV and Ep=7TeV)


Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2

● Existing ep: pp@LHC at y=0; eA: not even dAu@RHIC.● LHeC: clean scan of the LHC x-Q2 domain.


21

Salgado

d’Enterria(Ee=140GeV and Ep=7TeV)


Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2


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)2 (G

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-210

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1

10

210

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410

510 : QUltra-peripheral Q (|y| < 2.5)ΥLHC

(|y| < 2.5)ΨLHC J/

Nuclear DIS & DY data:NMC (DIS)SLAC-E139 (DIS)FNAL-E665 (DIS)EMC (DIS)FNAL-E772 (DY)

(Pb, b=0 fm)2sQ

perturbative

non-perturbative

Contents:

QCD at the LHeC.

I. Introduction.





22



http://cern.ch/lhec

http://cern.ch/lhec



One example of EW process:

23

Roh

ini a

t D

IS20

12

QCD at the LHeC: 3. Precision QCD.

Parton densities:

24

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2

Valence quarksHERAPDF-like, GM VFNS


Parton densities:

24

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

10-5

10-4

10-3

10-2

10-1

x

un

ce

rta

inty

on

d/u

Q2 = 4 GeV2

H1 + BCDMS

LHeC ep

LHeC ep+ed

(relaxed low x assumptions in the fit)

Gluon


Parton densities:

24

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

10-5

10-4

10-3

10-2

10-1

x

un

ce

rta

inty

on

d/u

Q2 = 4 GeV2

H1 + BCDMS

LHeC ep

LHeC ep+ed

(relaxed low x assumptions in the fit)

Gluon

● Large improvement in proton and neutron PDFs, both at small and at large x.


DIS extractions of αs

Coupling constant:

25

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2

● Open issues on mc, scales, order of perturbation th.,...QCD at the LHeC: 3. Precision QCD.

DIS extractions of αs

Coupling constant:

25

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2

● Open issues on mc, scales, order of perturbation th.,...

● Substantial improvement in the less known coupling constant, combination with jets still pending.


● Compared to HERA: higher lumi plus better efficiencies.

Total cross sections in ep collisions

10-3

10-2

10-1

1

10

102

103

104

105

106

8 9 10 20 30 40 50 60 70 80 90 100 200 300

20 30 50 70 100 200

10-3

10-2

10-1

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101

102

103

104

105

106 Charm γp

Charm DIS

Beauty γpBeauty DIS

tt γptt DIS

bW → tbW → t

CC e-p

sW → cCC e+p

sW → c

Ee (GeV)

σ (p

b)

10

102

103

104

105

106

107

108

109

1010

Even

ts pe

r 10

fb-1

LHeCHERA

Heavy flavors:

26

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

2


● Compared to HERA: higher lumi plus better efficiencies.

Total cross sections in ep collisions

10-3

10-2

10-1

1

10

102

103

104

105

106

8 9 10 20 30 40 50 60 70 80 90 100 200 300

20 30 50 70 100 200

10-3

10-2

10-1

1

101

102

103

104

105

106 Charm γp

Charm DIS

Beauty γpBeauty DIS

tt γptt DIS

bW → tbW → t

CC e-p

sW → cCC e+p

sW → c

Ee (GeV)

σ (p

b)

10

102

103

104

105

106

107

108

109

1010

Even

ts pe

r 10

fb-1

LHeCHERA

Heavy flavors:

26

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

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t, C

ERN

201

2


x=0.0001

x=0.00025

x=0.00035

x=0.0005

x=0.001

x=0.0025

x=0.0035

x=0.005

x=0.01

x=0.012

x=0.018

x=0.025

x=0.040

x=0.055

x=0.08

Q2/GeV

2

an

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ty [

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2 10 fb

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102

103

104

10510

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10-1

100

101

102

103

104

105

106

107

108

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ty [

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LHeC e-p 60*7000 GeV

2 10 fb

-1

102

103

104

10510

-2

10-1

100

101

102

103

104

105

106

107

108

Jets:

27

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

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201

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● Jets: large ET even in eA.● Useful for studies of parton dynamics in nuclei (hard probes), and for photon structure.● Background subtraction, detailed reconstruction pending.


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*4)/2M2N)"9"N2+/7 <O.1C<F2M2!9%2+/7 !"2P5#!

!"" Q2@' Q2$"""""26/7'

"9! Q2R2Q2"9N*+,-./01 S2'"26/7,2#'2Q Q2&

T2UV(.;G0<V10;G2T2W2/XHU9A+*@Y9!2ZB[<\]'2M2\['2M2@

'

>^/A2C!")P5F^*]_2C"9$)P5FC<1V192/..;.2;GIRF

L/12/G/.`R2<HVI/2JGH/.1V0G1R2C!)&aF

EHVI/2)21;1VI21U/;92/..;.

Photoproduction cross section:

28

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● Small angle electron detector 62 m far from the interaction point: Q2<0.01 GeV, y∼0.3 ⇒ W∼0.5 √s.

● Substantial enlarging of the lever arm in W.

Pancheri et al ‘08


Implications for UHEν’s:

29

● ν-n/A cross section (τ energy loss) dominated by DIS structure functions / (n)pdfs at small-x and large (small) Q2.● Key ingredient for estimating fluxes.

σtotνn

Preliminary; LHeC Design Study Report, CERN 2012QCD at the LHeC: 3. Precision QCD.

Contents:I. Introduction.





30



QCD at the LHeC.

http://cern.ch/lhec

http://cern.ch/lhec



ep inclusive: comparison

31

● Extensive model comparison: LHeC will have discriminative power.● Note: size of radiative corrections pending(see the talk by Spiesberger at DIS2012).


x-610 -510 -410 -310 -210 -110 1

)2 (G

eV2

Q

1

10

210

310

410

NMC-pdNMCSLACBCDMSZEUSH1CHORUSFLH108NTVDMNZEUS-H2LHeC_F2+FL

QCD at the LHeC: 4. Small x and eA.

ep inclusive: extracting the glue

32

● LHeC substantially reduces the uncertainties in global fits: FL and heavy flavor decomposition most useful.

Prel

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33

● Tension between F2 and FL in DGLAP fits as a sign of physics beyond standard DGLAP (GBW and CGC models).


ep inclusive: searching


33

● Tension between F2 and FL in DGLAP fits as a sign of physics beyond standard DGLAP (GBW and CGC models).


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1e-06 1e-05 0.0001

F Lp (x

,Q2 )

x

Q2=2 GeV2

LHeC AAMS09NNPDF fit

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1e-06 1e-05 0.0001 0.001x

Q2=5 GeV2


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1e-05 0.0001 0.001

F Lp (x

,Q2 )

x

Pseudo-data from AAMS09 (BK + running coupling)

Q2=13.5 GeV2


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1e-05 0.0001 0.001x

Pseudo-data from AAMS09 (BK + running coupling)

Q2=30 GeV2


ep inclusive: searching


eA inclusive: comparison

34

● Good precision can be obtained for F2(c,b) and FL at small x (Glauberized 3-5 flavor GBW model, NA ’02).

F2cPb F2bPb

-510 -410 -310 -210 -1100

0.2

0.4

0.6

0.8

1

1.2

x

)2(x,5 GeVLF

PbR

EPS09nDSHKN07

FGS10AKST

Data: LHeC

Prel

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-510 -410 -310 -210 -1100

0.2

0.4

0.6

0.8

1

1.2

x

)2(x,5 GeV2F

PbR

EPS09nDSHKN07

DSSZFGS10AKST

Data: LHeC


eA inclusive: constraining pdfs

35

● F2 data substantially reduce the uncertainties in DGLAP analysis; inclusion of charm, beauty and FL done.


36

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2● F2 data substantially reduce the uncertainties in DGLAP analysis; inclusion of charm, beauty and FL produce minor improvements.

eA inclusive: constraining pdfs


Note: FL in eA

37

● FL traces the nuclear effects on the glue (Cazarotto et al ’08).● Uncertainties in the extraction of F2 due to the unknown nuclear effects on FL of order 5 % (larger than expected stat.+syst.) ⇒

measure FL or use the reduced cross section (but then ratios at two energies...).

NA, Paukkunen, Salgado, Tywoniuk, ‘10


ep diffractive pseudodata:

38

● Large increase in the M2, xP=(M2-t+Q2)/(W2+Q2), β=x/xP region studied.● Possibility to combine LRG and LPS.

e

10 3

10 4

10 5

10 6

10 7

10 8

0 50 100 150 200 250

LHeC (Ee = 50 GeV, 2 fb-1)

HERA (500 pb-1)

Diffractive event yield (xIP < 0.05, Q2 > 1 GeV2)

MX / GeV

Even

ts

Prel

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ep diffractive pseudodata:

38

● Large increase in the M2, xP=(M2-t+Q2)/(W2+Q2), β=x/xP region studied.● Possibility to combine LRG and LPS.

e

10 3

10 4

10 5

10 6

10 7

10 8

0 50 100 150 200 250

LHeC (Ee = 50 GeV, 2 fb-1)

HERA (500 pb-1)

Diffractive event yield (xIP < 0.05, Q2 > 1 GeV2)

MX / GeV

Even

ts

Note: diffraction in ep is linked to shadowing in eA(Gribov): FGS, Capella-Kaidalov et al,...

Prel

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Diffraction and non-linear dynamics:

39

0

0.02

0.04

0.06

0.08

0.1

10-2

10-1

xIP=0.00001Q2=3 GeV2x IP

F 2D

10-2

10-1

xIP=0.0001Q2=3 GeV2

10-3

10-2

10-1

xIP=0.001Q2=3 GeV2

0

0.05

0.1

0.15

10-2

10-1

10-2

10-1

xIP=0.0001Q2=30 GeV2

10-2

10-1

xIP=0.001Q2=30 GeV2

0

0.02

0.04

0.06

0.08

0.1

10-1

H1 fit BipsatbCGC

Ee=150 GeV, 1o

10-1

10-2

10-1

xIP=0.001Q2=300 GeV2

0

0.05

0.1

0.15

10-2

10-1


F 2D

10-2

10-1

xIP=0.0001Q2=3 GeV2

10-2

10-1

xIP=0.001Q2=3 GeV2

0

0.025

0.05

0.075

0.1

10-2

10-1

10-2

10-1

xIP=0.0001Q2=30 GeV2

10-2

10-1

xIP=0.001Q2=30 GeV2

0

0.02

0.04

0.06

0.08

0.1

10-1

H1 fit BipsatbCGC

Ee=50 GeV, 1o

10-1

10-1

xIP=0.001Q2=300 GeV2

● Dipole models show differences with linear-based extrapolations (HERA-based dpdf’s) and among each other: possibility to check saturation and its realization.

Prel

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LHeC

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β βQCD at the LHeC: 4. Small x and eA.

Diffractive dijets:

40

● Diffractive dijet and open heavy flavour production offer large possibilities for:→ Checking factorization in hard diffraction.→ Constraining DPDFs.

● Large yields upto large pTjet.

● Direct and resolved contributions: photon PDFs.Pr

elim

inar

y; LH

eC D

esig

n St

udy

Rep

ort,

CER

N 2

012


p(P) )Y

Y (P

IPx

IPz (v)

* (q)γ (u)

e(k) e(k’)

jet

jet)

XX(P

GAP

remnant

e(k) e(k’)

* (q)γ

(u)

jet 12M )X

X(P

(v)IPz

remnant

GAP

p(P) )Y

Y (P

jet

remnant

(a) (b)

12M

IPx

[GeV]jet1TP

15 20 25 30 35 40 45 50 55

]-1

[fb

GeV

jet1

T/d

Pσd

-510

-410

-310

-210

-110

1

10

210

310

410 ]-1

[GeV

jet1

TdN

/dE

-310

-210

-110

1

10

210

310

410

510

610

[GeV]jet1TP

15 20 25 30 35 40 45 50 55

]-1

[fb

GeV

jet1

T/d

Pσd

-510

-410

-310

-210

-110

1

10

210

310

410)-1>2 (100 fb2Diffractive DIS Q

NLOJET++ (NLO)

Diffractive DIS on nuclear targets:

41

● Challenging experimental problem, requires Monte Carlo simulation with detailed understanding of the nuclear break-up.

● For the coherent case, predictions available.

0

0.05

0.1

0.15

10 -2


F 2D

10 -2

xIP=0.0001Q2=3 GeV2

10 -3 10 -1

xIP=0.001Q2=3 GeV2

10 -3 10 -1

xIP=0.01Q2=3 GeV2

00.020.040.060.08

0.1

10 -1 10 -1

xIP=0.0001Q2=30 GeV2

10 -2

xIP=0.001Q2=30 GeV2

10 -2

xIP=0.01Q2=30 GeV2

00.020.040.060.08

0.1

10 -1 10 -1 10 -2

xIP=0.001Q2=300 GeV2

10 -2

xIP=0.01Q2=300 GeV2

00.010.020.030.040.05

10-1

H1 fit BipsatbCGC

10-1

Pb

10-1

10-1

xIP=0.01Q2=3000 GeV2Pr

elim

inar

y; LH

eC D

esig

n St

udy

Rep

ort,

CER

N 2

012

βQCD at the LHeC: 4. Small x and eA.

Elastic VM production in ep:

42

● Most promising!!!

Prel

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Odderon:

43

● Odderon (C-odd exchange contributing to particle-antiparticle difference in cross section) seached inor through O-P interferences.

Prel

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● Sizable charge asymmetry, yields and reconstruction pending.

Elastic VM production in eA:

44

● Many interesting features in the nuclear case (see also Lappi et al ‘10, Horowitz ’11).

Prel

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!*A " J/# A

W (GeV)

1/A

2 d

$/d

t (

µb

/GeV

2)

0

0.5

1

1.5

2

2.5

0 200 400 600 800 1000

DVCS:

45

● Exclusive processes like γ*+h→ρ,ϕ,γ+h give information of GPDs, whose Fourier transform gives a tranverse scanning of the hadron: key importance for both non-perturbative and perturbative aspects, like the possibility of non-linear dynamics.

● Only small-x case where higher luminosity really helps!!!DVCS, Ee=50 GeV, 1o,pTγ,cut=2 GeV, 1 fb-1

DVCS, Ee=50 GeV, 10o,pTγ,cut=5 GeV, 100 fb-1

Preliminary; LHeC Design Study Report, CERN 2012QCD at the LHeC: 4. Small x and eA.

]2 [GeV2Q100 200 300 400 500 600 700

]2dx

[pb/

GeV

2/d

Qσ2

d4Q 1

10

210

x=1.3e-04x=2.4e-04x=4.2e-04x=7.5e-04

x=1.3e-03x=2.4e-03x=4.2e-03x=7.5e-03

]2 [GeV2Q5 10 15 20 25 30 35 40

]2dx

[pb/

GeV

2/d

Qσ2

d4Q

210

310 x=4.7e-05x=1.1e-04x=2.4e-04x=5.3e-04

x=1.2e-03x=2.7e-03x=6.0e-03x=1.3e-02

Transversity GPDs:

46

● Chiral-odd transversity GPDs are largely unknown.

● They can be accessed through double exclusive production:

Preliminary; LH

eC D


ERN

2012


10-4

10-3

10-2

10-1

100

101

102

103

104

105

10-5 10-4 10-3 10-2 10-1 100

d!

/dp

T2 d

t d

" [nb G

eV

-4]

"

pT2 = 2 GeV2

4 GeV2

6 GeV2

10-4

10-3

10-2

10-1

100

101

102

103

10-5 10-4 10-3 10-2 10-1 100

d!

/dp

T2 d

t d

" [

nb

Ge

V-4

]

"

Q2 = 2 GeV2

4 GeV2

6 GeV2

! "0

"+

p T

r

J

S

IP

p nF

Dijet azimuthal decorrelation:

47

● Studying dijet azimuthal decorrelation or forward jets (pT∼Q) would allow to understand the mechanism of radiation:→ kT-ordered: DGLAP.→ kT-disordered: BFKL.→ Saturation?● Further imposing a rapidity gap(diffractive jets) would be mostinteresting: perturbativelycontrollable observable.

Preliminary; LHeC Design Study

Report, CERN 2012

103

104

105

106

107

108

109

1010

d2 !

/dxd

|"#|

(pb

)

1 10-7

< x < 1 10-6

50 e x 7000 p

1 10-7

< x < 1 10-6

50 e x 7000 p

1 10-7

< x < 1 10-6

50 e x 7000 p

1 10-6

< x < 1 10-5

1 10-6

< x < 1 10-5

1 10-6

< x < 1 10-5

1 10-5

< x < 1 10-4

1 10-5

< x < 1 10-4

1 10-5

< x < 1 10-4

103

104

105

106

107

108

109

1010

1 2 3

1 10-4

< x < 1 10-3

1 10-4

< x < 1 10-3

1 10-4

< x < 1 10-3

1 2 3

"#

1 10-3

< x < 1 10-2

1 10-3

< x < 1 10-2

1 10-3

< x < 1 10-2

k = 0t

!"# < 120 o

!"#

j1

j2

j2

j1


Forward jets:

48

● Studying dijet azimuthal decorrelation or forward jets (pT∼Q) would allow to understand the mechanism of radiation:→ kT-ordered: DGLAP.→ kT-disordered: BFKL.→ Saturation?● Further imposing a rapidity gap(diffractive jets) would be mostinteresting: perturbativelycontrollable observable.


Report, CERN 2012


Dihadron azimuthal decorrelation:

49

● Dihadron azimuthal decorrelation is currently discussed at RHIC as one of the most suggestive indications of saturation.

● At the LHeC it could be studied far from the kinematical limits.


Report, CERN 2012


Albacete-Marquet ’10 pTlead>3 GeVpTass>2 GeVzlead=zass=0.3

y=0.7Q2=4 GeV2

50

● Low energy: need of hadronization inside → formation time, (pre-)hadronic absorption,...

● High energy: partonic evolution altered in the nuclear medium, partonic energy loss.

● The LHeC (νmax∼105 GeV) would allow to study the dynamics of hadronization, testing the parton/hadron eloss mechanism by introducing a length of colored material which would modify its pattern (length/nuclear size, chemical composition).

Brooks at Divonne’09

In-medium hadronization (I):


5o<θπ<25o, xπ>0.01

Daleo et al. ’04Data: H1 ’04

formation timeeffects

In-medium hadronization (II):

51

● Large (NLO) yields at small-x (H1 cuts, 3 times higher if relaxed).● Nuclear effects in hadronization at small ν (LO plus QW, Arleo ’03).



51



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0

1500

3000

4500

6000

0

200

400

600

d!

"/d

xB

(nb

)

2 # Q2 # 8 GeV

2MSTW-DSS (ep)

MSTW-DSS (ePb)

nDS-DSS (ePb)

nDS-nFF (ePb)

EPS09-DSS (ePb)

60+7000

60+2750

8 # Q2 # 20 GeV

2

xBj

20 # Q2 # 70 GeV

2

pT $ 3.5 GeV0

70

140

10-6

10-5

10-4

d!

"/d

pT

(pb

/GeV

)

2 # Q2 # 4.5 GeV

2

1

10

MSTW-DSS

MSTW-DSS (Pb)

nDSS-DSS (Pb)

nDS-nFF (Pb)

EPS-DSS (Pb)

60+7000

60+2750

4.5 # Q2 # 15 GeV

2

1

10

pT (GeV)

15 # Q2 #70 GeV

2

1

10

3 4 5 6 7 8 9 10 15


51



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Summary:

52

● Many issues open about precision pQCD and small-x physics.

● Pdfs: current ep experiments cover pp@LHC at y=0; in eA, not even dAu@RHIC is really constrained.

● An ep/eA collider offers huge possibilities to test our ideas about QCD: hadron structure, high-energy behavior, radiation,...

● eA: amplifier of density effects, implications on UrHIC complementary to pA@LHC.

● At an LHeC@CERN:➜ Unprecedented access to small x in p and A for pdfs.➜ Novel sensitivity to physics beyond standard pQCD.➜ Stringent tests of the dynamics of QCD radiation.➜ High precision tests of collinear factorization(s).➜ Transverse scanning of the hadron at small x.➜ ...

QCD at the LHeC.

53

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2Commitees and authors:

QCD at the LHeC.

53

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The LHeC Study Grouphttp://cern.ch/lhec

June 14-15 2012

Commitees and authors:

QCD at the LHeC.

http://cern.ch/lhec

http://cern.ch/lhec

Tentative timeline:

54QCD at the LHeC.

Tentative timeline:

54

Preliminary; LHeC Design Study Report, CERN 2012QCD at the LHeC.

Tentative timeline:

54


→ LHC death by radiation damage estimated by 2030-2035.

→ LHeC should work for ∼ 10 years.

→ No disturbance to LHC operation: built on surface, installation during LS3.

⇒QCD at the LHeC.

Tentative timeline:

54


→ LHC death by radiation damage estimated by 2030-2035.

→ LHeC should work for ∼ 10 years.

→ No disturbance to LHC operation: built on surface, installation during LS3.

⇒Thanks to the organizers for the invitation!!!

Thanks to you all for your attention!!!

QCD at the LHeC.

Backup:

55QCD at the LHeC.

The detector: some details

56QCD at the LHeC: 2. The Large Hadron Electron Collider.

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B. C

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at H

P201

2

/

Features in dAu@RHIC:

57

● Control experiment for initial state effects in AA: Cronin in dAu at midrapidity ruled out initial state effects as the explanation for the suppression observed in AA.● Suppression at forward rapidities predicted by small-x evolution.● Azymuthal decorrelation in the forward region also seen.

Albacete-Marquet ’10


/

Features in dAu@RHIC:

57

● Control experiment for initial state effects in AA: Cronin in dAu at midrapidity ruled out initial state effects as the explanation for the suppression observed in AA.● Suppression at forward rapidities predicted by small-x evolution.● Azymuthal decorrelation in the forward region also seen.

Albacete-Marquet ’10

● Saturation physics describes these data, but:➜ The normalization is not determined by the calculation ↔ problems to compute the b-dependence.

➜ A full NLO analysis is still missing.➜ RHIC data lie at the edge of phase space.

● Other descriptions exist: NLO pQCD (problems with pp reference), eloss models,...

● Note: these studies are very important to understand the mechanism of soft/semihard particle production: ridge, initial conditions for HIC, isotropization,...⇒ ‘benchmarking’

the bulk.


UPCs in pPb:

58

● Large luminosities in γp.● Interesting kinematical coverage.

1024

1025

1026

1027

1028

1029

1030

1031

1032

0 200 400 600 800 1000 1200 1400

L AB

n() [

cm-2

s-1]

s p [GeV]

p

Pb @PbPb

Pb

1023

1024

1025

1026

1027

1028

1029

1030

1031

1032

50 100 150 200 250 300 350 400

L AB

dL

/dW

[GeV

-1 c

m-2

s-1]

W [GeV]

PbPbpp (ALICE)

pp (Atlas, CMS)pPb


UPCs in pPb:

58

● Large luminosities in γp.● Interesting kinematical coverage.

1024

1025

1026

1027

1028

1029

1030

1031

1032

0 200 400 600 800 1000 1200 1400

L AB

n() [

cm-2

s-1]

s p [GeV]

p

Pb @PbPb

Pb

1023

1024

1025

1026

1027

1028

1029

1030

1031

1032

50 100 150 200 250 300 350 400

L AB

dL

/dW

[GeV

-1 c

m-2

s-1]

W [GeV]

PbPbpp (ALICE)

pp (Atlas, CMS)pPb

x -610 -510 -410 -310 -210 -110 1

)2 (G

eV2

Q

-210

-110

1

10

210

310

410

510 : QUltra-peripheral Q (|y| < 2.5)ΥLHC

(|y| < 2.5)ΨLHC J/

Nuclear DIS & DY data:NMC (DIS)SLAC-E139 (DIS)FNAL-E665 (DIS)EMC (DIS)FNAL-E772 (DY)

(Pb, b=0 fm)2sQ

perturbative

non-perturbative

Preliminary; LHeC Design Study Report, CERN 2012QCD at the LHeC: 2. The Large Hadron Electron Collider.


59

x-610 -510 -410 -310 -210 -110

)2 (G

eV2

Q

-110

1

10

210

310

410

510




NMC

E772

E139

E665

EMC

(Pb, b=0 fm)2sQ

perturbative

non-perturbative


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pA@LHC, Salgado et al., 1105.3919


Introduction:

60

● At the SPS and at RHIC, pA (dAu) runs have been an essential part of the heavy-ion programs. Prominent examples:

➜ SPS: J/ψ absorption in pA → anomalous suppression in PbPb.➜ RHIC: Cronin in dAu → jet quenching in AuAu as a final state effect.

● A pPb run @LHC with <L>∼1029(/3)cm-2s-1 for ∫Ldt∼0.1(/3)

pb-1 in the 2012 run (4.4-5 TeV/n instead of nominal 8.8).

● Rapidity shift (0.46) due to asymmetricsystem, smaller for dPb (0.12) but no injector:p+Pb and Pb+p (ALICE μ-arm, LHCb).

● All LHC experiments with capabilities for this running mode: ALICE, ATLAS, CMS, LHCb, LHCf,...

● Check in November 2011, approved in Chamonix last February.PHENIX, π0


Introduction:

60

● At the SPS and at RHIC, pA (dAu) runs have been an essential part of the heavy-ion programs. Prominent examples:

➜ SPS: J/ψ absorption in pA → anomalous suppression in PbPb.➜ RHIC: Cronin in dAu → jet quenching in AuAu as a final state effect.

● A pPb run @LHC with <L>∼1029(/3)cm-2s-1 for ∫Ldt∼0.1(/3)

pb-1 in the 2012 run (4.4-5 TeV/n instead of nominal 8.8).

● Rapidity shift (0.46) due to asymmetricsystem, smaller for dPb (0.12) but no injector:p+Pb and Pb+p (ALICE μ-arm, LHCb).

● All LHC experiments with capabilities for this running mode: ALICE, ATLAS, CMS, LHCb, LHCf,...

● Check in November 2011, approved in Chamonix last February.


pPb at the LHC:

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● Offers the best possibility (before lepton-ion colliders) to test:➜ The small-x glue far from the kinematical limits.➜ The production mechanism: clear differences between collinear factorization and saturation?

Jalilian-Marian & Rezaeian, 1110.2810QCD at the LHeC: 2. The Large Hadron Electron Collider.

Summary:

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● A pPb run at the LHC offers huge possibilities (unique before lA colliders) for:A) Benchmarking for the HIC program, particularly for reducing uncertainties coming from nPDFs:

B) Discovery: clarifying the relevance of saturation physics.

C) Others: UPCs, measurements of interest for UHECR.QCD at the LHeC: 2. The Large Hadron Electron Collider.

Summary:

62

● A pPb run at the LHC offers huge possibilities (unique before lA colliders) for:A) Benchmarking for the HIC program, particularly for reducing uncertainties coming from nPDFs:

B) Discovery: clarifying the relevance of saturation physics.

C) Others: UPCs, measurements of interest for UHECR.Ax

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qcd at the€¦ · qcd at the lhec. i. introduction. 2. the large hadron electron collider. 3....

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