opportunities with a Large Hadron-electron Collider at...
Transcript of opportunities with a Large Hadron-electron Collider at...
���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
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.
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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.
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Disclaimer: results from CDR as available on 27.07.2011 at 17.35 CERN time.
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
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
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?
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Two-pronged approach: ↓ x / ↑ A. eA: test/enhance density effects.
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Uncertainties in DGLAP npdf’s:
7Small-x physics at the LHeC: 1. Introduction.
Problem for benchmarking in hard probes!!!
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NLO analysis
Uncertainties in DGLAP npdf’s:
8Small-x physics at the LHeC: 1. Introduction.
Problem for benchmarking in hard probes!!!
J/ψALICE@QM2011
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
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.
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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
●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
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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
!"#$%&$'()*'+(),-'.-/'!"#$%&$'
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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.
Machine: Ring-Ring option
Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 13
BYPASS
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Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 14
BYPASS
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eD: LeN=ALeA>∼1031 cm-2s-1.
Machine: Linac-Ring option
Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 15
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Boga
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HeC
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500 MeV
HE LR, 140 GeV
HE LR, ER, 140 GeV
Machine: Linac-Ring option
Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 16
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HE LR, ER, 140 GeV
eD: LeN=ALeA>∼3×1031 cm-2s-1.Large L for e+ challenging.
The detector: low-x/eA setup
Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 17
e p
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5.9 m 3.6 m
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The detector: low-x/eA setup
Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 18
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The detector: low-x/eA setup
Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 19
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● Other detector options: low acceptance (8o-172o), solenoid outside, also considered.● Plus luminosity detector, electron tagging, polarimeter, ZDC and leading proton detector.
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Kinematics:
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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
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Salgado
Black: 920+30 Green: 100+20
Q2sat,GBW
2081/3Q2sat,GBW
Preliminary; LHeC Design Study Report, CERN 2011
Kinematics: LHC vs. LHeC
Small-x physics at the LHeC: 2. The Large Hadron-electron Collider. 23
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NMC
E772
E139
E665
EMC
(Pb, b=0 fm)2sQ
perturbative
non-perturbative
(70 GeV - 2.5 TeV)e-Pb (LHeC)
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● 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
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
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
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.
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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
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
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).
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● F2 data substantially reduce the uncertainties in DGLAP analysis; inclusion of charm, beauty and FL produce minor improvements.
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1● F2 data substantially reduce the uncertainties in DGLAP analysis; inclusion of charm, beauty and FL produce minor improvements.
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
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.
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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
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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.
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Diffraction and non-linear dynamics:
Small-x physics at the LHeC: 4. Diffractive observables. 36
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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.
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● Most promising!!!
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Elastic VM production (II):
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● Many interesting features in the nuclear case (see also Lappi et al ‘10, Horowitz ’11).
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1
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
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
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
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
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=
Rµ
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
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
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
Plans for the CDR:
47Small-x physics at the LHeC.
Prel
imin
ary;
LHeC
Des
ign
Stud
y R
epor
t, C
ERN
201
1
Plans for the CDR:
48Small-x physics at the LHeC.
Prel
imin
ary;
LHeC
Des
ign
Stud
y R
epor
t, C
ERN
201
1
Plans for the CDR:
49Small-x physics at the LHeC.
Prel
imin
ary;
LHeC
Des
ign
Stud
y R
epor
t, C
ERN
201
1
The LHeC Study Grouphttp://cern.ch/lhec
(8-11/11)
Tentative timeline:
50Small-x physics at the LHeC.
Preliminary; LHeC Design Study Report, CERN 2011
CERN
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.
⇒
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
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!!!
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)
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
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