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e Small-x physics opportunities with a Large Hadron-electron Collider at CERN Néstor Armesto Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela [email protected] for the LHeC Study Group, http://cern.ch/lhec , Working Group on Physics at High Parton Densities in ep and eA (with Brian Cole, Paul Newman and Anna Stasto) 1 PANIC11: The 19th Particles and Nuclei International Conference MIT, July 28th 2011
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opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

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Page 1: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

���e Small-x physics opportunities with a

Large Hadron-electron Collider at CERNNéstor Armesto

Departamento de Física de Partículas and IGFAE, Universidade de Santiago de [email protected]

for the LHeC Study Group, http://cern.ch/lhec,Working Group on Physics at High Parton Densities in ep and eA (with

Brian Cole, Paul Newman and Anna Stasto) 1

PANIC11: The 19th Particles and Nuclei International Conference

MIT, July 28th 2011

Page 2: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Contents:

Small-x physics at the LHeC.

I. Introduction.

2. The Large Hadron-electron Collider.

3. Inclusive observables:● ep inclusive pseudodata and their effect on pdf’s.● eA inclusive pseudodata and their effect on npdf’s.

4. Diffractive observables:● ep diffractive pseudodata.● Nuclear diffraction.● Exclusive vector meson production. ● DVCS.

5. Final states and photoproduction.

6. Summary and outlook.

See the EIC talks here by T. Horn, V. Ptitsyn and M. Stratmann, the LHeC talks at DIS2011 (https://wiki.bnl.gov/conferences/index.php/DIS-2011), and the talk by P. Laycock at HEP-EPS11.

2

Page 3: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Contents:

Small-x physics at the LHeC.

I. Introduction.

2. The Large Hadron-electron Collider.

3. Inclusive observables:● ep inclusive pseudodata and their effect on pdf’s.● eA inclusive pseudodata and their effect on npdf’s.

4. Diffractive observables:● ep diffractive pseudodata.● Nuclear diffraction.● Exclusive vector meson production. ● DVCS.

5. Final states and photoproduction.

6. Summary and outlook.

See the EIC talks here by T. Horn, V. Ptitsyn and M. Stratmann, the LHeC talks at DIS2011 (https://wiki.bnl.gov/conferences/index.php/DIS-2011), and the talk by P. Laycock at HEP-EPS11.

3

Disclaimer: results from CDR as available on 27.07.2011 at 17.35 CERN time.

Page 4: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

High-energy QCD:

4

Our aims: understanding

● The implications of unitarity in a QFT.

● The behavior of QCD at large energies / hadron wave function at small x.

● The initial conditions for the creation of a dense medium in heavy-ion collisions: nuclear WF + initial stage.

Small-x physics at the LHeC: 1. Introduction.

Where do the availableexperimental data lie?

Non-linear

Linear

Page 5: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

High-energy QCD:

5

Our aims: understanding

● The implications of unitarity in a QFT.

● The behavior of QCD at large energies / hadron wave function at small x.

● The initial conditions for the creation of a dense medium in heavy-ion collisions: nuclear WF + initial stage.

Small-x physics at the LHeC: 1. Introduction.

Where do the availableexperimental data lie?

Non-linear

Linear

Our aims: understanding

● The implications of unitarity in a QFT.

● The behavior of QCD at large energies / hadron wave function at small x.

● The initial conditions for the creation of a dense medium in heavy-ion collisions: nuclear WF + initial stage.

Hadron wave function

Source (frozen)

Classical,Aμ∝1/αs

O(αs)

Saturation / CGC

Page 6: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

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:

Small-x physics at the LHeC: 1. Introduction.

● 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).

● Unitarity (non-linear effects): where?

6

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

Page 7: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

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FGS10)2=4 GeV2(Q

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

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PbR

EPS09nDSHKN07

FGS10

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)2(x,100 GeVuPbR

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1

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x

)2(x,100 GeVgPbR

NLO analysis

Uncertainties in DGLAP npdf’s:

7Small-x physics at the LHeC: 1. Introduction.

Problem for benchmarking in hard probes!!!

Page 8: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

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)2(x,1.69 GeVvu

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EPS09nDSHKN07

FGS10)2=4 GeV2(Q

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

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)2(x,1.69 GeVuPbR

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)2(x,1.69 GeVgPbR

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)2(x,100 GeVvu

PbR

EPS09nDSHKN07

FGS10

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

0.2

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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

Uncertainties in DGLAP npdf’s:

8Small-x physics at the LHeC: 1. Introduction.

Problem for benchmarking in hard probes!!!

J/ψALICE@QM2011

Page 9: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Contents:

Small-x physics at the LHeC.

I. Introduction:

2. The Large Hadron-electron Collider.

3. Inclusive observables:● ep inclusive pseudodata and their effect on pdf’s.● eA inclusive pseudodata and their effect on npdf’s.

4. Diffractive observables:● ep diffractive pseudodata.● Nuclear diffraction.● Exclusive vector meson production. ● DVCS.

5. Final states and photoproduction.

6. Summary and outlook.

9

Page 10: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Project:

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 10

●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)

d’Enterria

Page 11: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

●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.

Project:

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 11

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)

d’Enterria

Dainton

Page 12: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

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

!0-&%$%1)'234'()*'

56-&701/-(8'!"#$%&$'

.9&6-(0''

:709&790-''

;'4#)(<%&$'

=%,"'!(071)'4-)$%>-$'

?(0,-'@'

!(071)$'

Physics goals:

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 12

● 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.

Page 13: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Machine: Ring-Ring option

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 13

BYPASS

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

1

Page 14: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Machine: Ring-Ring option

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 14

BYPASS

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

1

eD: LeN=ALeA>∼1031 cm-2s-1.

Page 15: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Machine: Linac-Ring option

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 15

Prel

imin

ary;

Boga

cz@

DIS

11; L

HeC

D

esig

n St

udy

Rep

ort,

CER

N 2

011

500 MeV

HE LR, 140 GeV

HE LR, ER, 140 GeV

Page 16: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Machine: Linac-Ring option

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 16

Prel

imin

ary;

Boga

cz@

DIS

11; L

HeC

D

esig

n St

udy

Rep

ort,

CER

N 2

011

500 MeV

HE LR, 140 GeV

HE LR, ER, 140 GeV

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

Page 17: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

The detector: low-x/eA setup

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 17

e p

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

1 RR, high acceptance

5.9 m 3.6 m

2.6 m

Page 18: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

The detector: low-x/eA setup

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 18

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

1 RR, high acceptanceLR

e p

Page 19: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

The detector: low-x/eA setup

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 19

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

1 RR, high acceptanceLR

e p

Page 20: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

The detector: low-x/eA setup

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 20

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

1 RR, high acceptanceLR

e p

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

Page 21: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

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:

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 21Ax

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)2

(G

eV

2Q

1

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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

Page 22: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

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:

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 22Ax

-510 -410

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)2

(G

eV

2Q

1

10

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310

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510

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|<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 2011

Page 23: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Kinematics: LHC vs. LHeC

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 23

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)

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

1

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

pA@LHC, Salgado et al., 1105.3919

Page 24: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Contents:

Small-x physics at the LHeC.

I. Introduction:

2. The Large Hadron-electron Collider.

3. Inclusive observables:● ep inclusive pseudodata and their effect on pdf’s. (M. Klein, J. Albacete, NA, J. Rojo, P. Newman, J. Forshaw, G. Soyez)● eA inclusive pseudodata and their effect on npdf’s. (M. Klein, NA, H. Paukkunen, K. Eskola, C. A. Salgado)

4. Diffractive observables:● ep diffractive pseudodata.● Nuclear diffraction.● Exclusive vector meson production. ● DVCS.

5. Final states and photoproduction.

6. Summary and outlook.

24

Page 25: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

ep inclusive pseudodata (I):

Small-x physics at the LHeC: 3. Inclusive observables. 25

● Extensive model comparison (Albacete): LHeC will have discriminative power.

● Note: size of radiative corrections pending.

Preliminary; LHeC Design Study Report, CERN 2011

Page 26: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

ep inclusive pseudodata (II):

Small-x physics at the LHeC: 3. Inclusive observables. 26

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

Prel

imin

ary;

LHeC

Des

ign

Stud

y R

epor

t, C

ERN

201

1

Page 27: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

ep inclusive pseudodata (III):

Small-x physics at the LHeC: 3. Inclusive observables. 27

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

Preliminary; LHeC Design Study Report, CERN 2011

Page 28: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

ep inclusive pseudodata (III):

Small-x physics at the LHeC: 3. Inclusive observables. 28

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

Preliminary; LHeC Design Study Report, CERN 2011

Page 29: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

eA inclusive pseudodata (I):

Small-x physics at the LHeC: 3. Inclusive observables. 29

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

F2cPb F2bPb

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)2(x,5 GeV2F

PbR

EPS09nDSHKN07

FGS10AKST

Data: LHeC

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0.2

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)2(x,5 GeVLF

PbR

EPS09nDSHKN07

FGS10AKST

Data: LHeC

Prel

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ary;

LHeC

Des

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eA inclusive pseudodata (II):

Small-x physics at the LHeC: 3. Inclusive observables. 30

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

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Page 31: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

eA inclusive pseudodata (II):

Small-x physics at the LHeC: 3. Inclusive observables. 31

Prel

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

Page 32: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Note: FL in eA

Small-x physics at the LHeC: 3. Inclusive observables. 32

● 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

Page 33: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Contents:

Small-x physics at the LHeC.

I. Introduction:

2. The Large Hadron-electron Collider.

3. Inclusive observables:● ep inclusive pseudodata and their effect on pdf’s.● eA inclusive pseudodata and their effect on npdf’s.

4. Diffractive observables:● ep diffractive pseudodata. (P. Newman)● Nuclear diffraction. (H. Kowalski, C. Marquet)● Exclusive vector meson production. (P. Newman, G. Watt, A. Stasto, C. Weiss)● DVCS. (L. Favart, P. Newman)

5. Final states and photoproduction.

6. Summary and outlook.

33

Page 34: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

ep diffractive pseudodata:

Small-x physics at the LHeC: 4. Diffractive observables. 34

● 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

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e

ep diffractive pseudodata:

Small-x physics at the LHeC: 4. Diffractive observables. 35

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

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,...

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Page 36: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Diffraction and non-linear dynamics:

Small-x physics at the LHeC: 4. Diffractive observables. 36

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

xIP=0.00001Q2=3 GeV2x IP

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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β β

Page 37: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Diffractive DIS on nuclear targets:

Small-x physics at the LHeC: 4. Diffractive observables. 37

● 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

xIP=0.00001Q2=3 GeV2x IP

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

011

β

Page 38: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Elastic VM production (I):

Small-x physics at the LHeC: 4. Diffractive observables. 38

● Most promising!!!

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Elastic VM production (II):

Small-x physics at the LHeC: 4. Diffractive observables. 39

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

Prel

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Page 40: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

DVCS:

Small-x physics at the LHeC: 4. Diffractive observables. 40

● 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 2011

Page 41: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Contents:

Small-x physics at the LHeC.

I. Introduction:

2. The Large Hadron-electron Collider.

3. Inclusive observables:● ep inclusive pseudodata and their effect on pdf’s. ● eA inclusive pseudodata and their effect on npdf’s.

4. Diffractive observables:● ep diffractive pseudodata.● Nuclear diffraction.● Exclusive vector meson production. ● DVCS.

5. Final states and photoproduction. (NA, B. Cole, J. Collins, H. Jung, P. Newman, A. Stasto)

6. Summary and outlook.

41

Page 42: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

In-medium hadronization:

Small-x physics at the LHeC: 5. Final states and photoproduction. 42

● 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

Page 43: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Forward jets:

Small-x physics at the LHeC: 5. Final states and photoproduction. 43

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

Preliminary; LHeC Design Study Report, CERN 2011

Page 44: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Jet photoproduction:

Small-x physics at the LHeC: 5. Final states and photoproduction. 44

● 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.

50 100 150 200 250

-1110

-1010

-910

-810

-710

-610

-510

-410

-310

-210

-110

1

10

210

310

410

510

610 per nucleon)GeV

bµ (TjetdE

=02Qjetσd

(GeV)TjetE

NLO QCD

/2Tjet

E∑=Fµ=

pdf: GRV-HOγ

-algorithm, D=1Tk

)o<175jetθ<o|<3.1 (5jetη|

per

nuc

leon

-1Ev

ents

for 2

fb

-3 -2 -1 0 1 2 3

-410

-310

610

b per nucleon)µ (jetηd

=02Qjetσd

jetη

>20 GeVTjetE

e(50)+p(7000), CTEQ6.1M

e(50)+Pb(2750), CTEQ6.1M

e(50)+Pb(2750), CTEQ6.1M+EPS09

per

nuc

leon

-1Ev

ents

for 2

fbPreliminary; LHeC Design Study Report, CERN 2011

Page 45: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Total γp cross section:

Small-x physics at the LHeC: 5. Final states and photoproduction. 45

● 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

Preliminary; LHeC Design Study Report, CERN 2011

Page 46: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Summary:

Small-x physics at the LHeC. 46

● Many issues remain open about small-x physics (behavior of the hadron wave function at small x): describable by pQCD?, need of resummation/onset of unitarity in the accessible kinematical regions?

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

● An electron-nucleon/ion collideroffers huge possibilities to test ourideas about high-energy QCD. eA:amplifier of density effects,implications on UrHICcomplementary to pA@LHC.

● LHeC@CERN: new facility forep/eA at Ecm∼1-2 TeV under design.

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)

d’Enterria

Page 47: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Plans for the CDR:

47Small-x physics at the LHeC.

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Plans for the CDR:

48Small-x physics at the LHeC.

Prel

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LHeC

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Page 49: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Plans for the CDR:

49Small-x physics at the LHeC.

Prel

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LHeC

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

(8-11/11)

Page 50: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Tentative timeline:

50Small-x physics at the LHeC.

Preliminary; LHeC Design Study Report, CERN 2011

CERN

Page 51: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Tentative timeline:

51Small-x physics at the LHeC.

Preliminary; LHeC Design Study Report, CERN 2011

CERN

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

→ LHeC should work for 10 years.

→ No disturbance to LHC operation: installation during stops.

Page 52: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Tentative timeline:

52Small-x physics at the LHeC.

Preliminary; LHeC Design Study Report, CERN 2011

CERN

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

→ LHeC should work for 10 years.

→ No disturbance to LHC operation: installation during stops.

⇒LHeC tentative timeline

Page 53: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Tentative timeline:

53Small-x physics at the LHeC.

Preliminary; LHeC Design Study Report, CERN 2011

CERN

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

→ LHeC should work for 10 years.

→ No disturbance to LHC operation: installation during stops.

⇒LHeC tentative timeline

Many thanks to Max Klein, Brian Cole, Paul Newman, Anna Stasto, Urs Wiedemann, Paul Laycock, John Dainton, Peter Kotska, Miriam Fitterer, John Jowett, Alex Bogacz, Javier Albacete, David d’Enterria, Kari Eskola, Cyrille Marquet, Hannu Paukkunen, Carlos Salgado, Mark Strikman, Konrad Tywoniuk and all other collaborators in the preparation of the CDR!!!

Page 54: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Backup:

54Small-x physics at the LHeC.

Page 55: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

Kinematics: LHC vs. LHeC

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 55

Salgado

d’Enterria(Ee=140GeV  and  Ep=7TeV)

Page 56: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

LHeC scenarios:

Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 56

● 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

Page 57: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

ep inclusive pseudodata (0):

Small-x physics at the LHeC: 3. Inclusive observables. 57

● Charm and beauty most important (HERApdf; systematics half than at H1).

Q2/GeV2

F 2c 5j

c=0.1, bgdq=0.01

LHeC

100 101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

107

Q2/GeV2

F 2c 5j

.

LHeC

100 101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

107

Q2/GeV2

F 2c 5j

c=0.1, bgdq=0.01

LHeC

100 101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

107

Q2/GeV2

F 2c 5j

.

LHeC

100 101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

107

Q2/GeV2

F 2c 5j

c=0.1, bgdq=0.01

LHeC

100 101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

107

Q2/GeV2

F 2c 5j

.

LHeC

100 101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

107

x=0.000007x=0.00003

x=0.00007

x=0.0003

x=0.0007

x=0.003

x=0.007

x=0.03

x=0.1

x=0.3

Q2/GeV2

F 2b 5j

b=0.5, bgdc=0.1

LHeC

101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

Q2/GeV2

F 2b 5j

.

LHeC

101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

Q2/GeV2

F 2b 5j

b=0.5, bgdc=0.1

LHeC

101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

Q2/GeV2

F 2b 5j

.

LHeC

101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

Q2/GeV2

F 2b 5j

b=0.5, bgdc=0.1

LHeC

101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

Q2/GeV2

F 2b 5j

.

LHeC

101 102 103 104 105 10610-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104 x=0.00003x=0.00007

x=0.0003

x=0.0007

x=0.003

x=0.007

x=0.03

x=0.1

x=0.3

Preliminary; LHeC Design Study Report, CERN 2011

Page 58: opportunities with a Large Hadron-electron Collider at CERNlhec.web.cern.ch/sites/lhec.web.cern.ch/files/armesto.panic11.pdfProject: Small-x physics at the LHeC: 2. The Large Hadron-electron

eA inclusive pseudodata (0):

Small-x physics at the LHeC: 3. Inclusive observables. 58

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

Paukkunen