25th International Nuclear Physics Conference INPC2013 Firenze, June 4th (GeV. at the LHeC: Néstor Armesto

Transcription

1 5th International Nuclear Physics Conference INPC013 Firenze, June 4th 013 LHeC - Low x Kinematics Q /GeV e Small-x Physics in ea 6 nuclear DIS - F,A (x,q ) Proposed facilities: 5 LHeC at the LHeC: Fixed-target data: NMC 4 E77 E139 Understanding 3 the E665 e-pb (LHeC) EMC (70 GeV -.75 TeV) ) (GeV Q 1 Initial State Q s of URHIC (Pb, b=0 fm) Néstor Armesto x 1-1 perturbative non-perturbative Departamento -1 de Física de Partículas and IGFAE, Universidade de Santiago de Compostela and CERN, Physics Department, Theory Unit nestor.armesto@usc.es for the LHeC Study group, 1 x 1

2 Contents: I. Motivation.. ea at the LHeC and comparison to the LHC. 3. Physics case in ea: Inclusive measurements and nuclear PDFs. Diffraction. Final states: dynamics of QCD radiation and hadronization. 4. Summary and outlook. CDR, arxiv: , J. Phys. G 39 (01) ; arxiv: ; arxiv:111.5; LHeC talks at DIS013 and LPCC Small-x in ea at the LHeC.

3 npdfs: R = f i/a Af i/p measured expected if no nuclear effects Lack of data models give vastly different results for the nuclear glue at small scales and x: problem for benchmarking in HIC. Yellow Report on Hard Probes, R Pb u v (x,1.69 GeV ) R Pb u (x,1.69 GeV ) R Pb g (x,1.69 GeV ) Available DGLAP analysis at NLO show large uncertainties at small scales and x R -5-5 EPS09 nds HKN07 Pb u v (x,0 GeV EPS09 nds HKN ) - DSSZ FGS (Q =4 GeV ) -1 1 x DSSZ FGS -1 1 x NLO analysis x R Pb u -5 (x,0 GeV -4-3 ) x R -5 Pb g (x,0 GeV -3 - ) x -1 1 x Small-x in ea at the LHeC: 1. Motivation. 3

4 npdfs: R = f i/a Af i/p measured expected if no nuclear effects Lack of data models give vastly different results for the nuclear glue at small scales and x: problem for benchmarking in HIC. Yellow Report on Hard Probes, R Pb u v (x,1.69 GeV ) R Pb u (x,1.69 GeV ) R Pb g (x,1.69 GeV ) Available DGLAP analysis at NLO show large uncertainties at small scales and x R -5 u v EPS09 nds HKN07 Pb -4-3 (x,0 GeV EPS09 nds HKN07 - ) DSSZ FGS (Q =4 GeV ) -1 1 x DSSZ FGS NLO analysis x Inclusive J/ψ, x x R Pb u (x,0 GeV ) R -5 Pb g (x,0 GeV -3 - ) x -1 1 x Small-x in ea at the LHeC: 1. Motivation. 3

5 Relevance for the HI program: Small-x in ea at the LHeC: 1. Motivation. 4

6 Relevance for the HI program: Nuclear wave function at small x: nuclear structure functions. Small-x in ea at the LHeC: 1. Motivation. 4

7 Relevance for the HI program: Nuclear wave Particle production at the very beginning: which factorisation in ea? function at small x: How does the system nuclear behave as isotropised structure so fast?: initial conditions functions. for plasma formation to be studied in ea. Small-x in ea at the LHeC: 1. Motivation. 4

8 Relevance for the HI program: Nuclear wave Particle production at the very beginning: which factorisation in ea? function at small x: How does the system nuclear behave as isotropised structure so fast?: initial conditions functions. for plasma formation to be studied in ea. Small-x in ea at the LHeC: 1. Motivation. Probing the medium through energetic particles (jet quenching etc.): modification of QCD radiation and hadronization in the nuclear medium. 4

9 Contents: I. Motivation.. ea at the LHeC and comparison to the LHC. 3. Physics case in ea: Inclusive measurements and nuclear PDFs. Diffraction. Final states: dynamics of QCD radiation and hadronization. 4. Summary and outlook. CDR, arxiv: , J. Phys. G 39 (01) ; arxiv: ; arxiv:111.5; LHeC talks at DIS013 and LPCC Small-x in ea at the LHeC. 5

10 Physics goals: Proton structure to a few -0 m: Q lever arm. Precision QCD/EW physics. Higgs physics. High-mass frontier (lq, 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. Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 6

11 Accelerator: Design considerations: L~ 33 cm - s -1. s 0.8 TeV/nucleon Power < 70 MW. Synchronous pp/ep. Ee=60 GeV (benchmark). Luminosity per nucleon CDR numbers for luminosity, to be considered now as lower bounds. ed: LeN=ALeA> 3 31 cm - s -1 Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 7

12 Accelerator: s 0.8 TeV/nucleon Luminosity per nucleon CDR numbers for luminosity, to be considered now as lower bounds. ed: LeN=ALeA> 3 31 cm - s -1 Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 7

13 LHC vs. LHeC: ) (GeV Q p+pb LHC (7 TeV+.75 TeV) Present nuclear DIS and Drell-Yan in p+a ppb@lhc y lab = 4 y lab = y lab = 0 ) (GeV Q nuclear DIS - F,A (x,q ) Proposed facilities: LHeC Fixed-target data: NMC E77 E139 E665 EMC epb@lhec e-pb (LHeC) (70 GeV -.75 TeV) Q sat,pb (x) y lab = 6 Present DIS+DY Q s (Pb, b=0 fm) x A perturbative non-perturbative ) (GeV Q 5 Ultra-peripheral QQ: 4 3 LHC Υ ( y <.5) LHC J/Ψ ( y <.5) Nuclear DIS & DY data: NMC (DIS) SLAC-E139 (DIS) FNAL-E665 (DIS) EMC (DIS) FNAL-E77 (DY) PbPb@LHC x 1 Q s (Pb, b=0 fm) perturbative non-perturbative x Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 8

14 LHC vs. LHeC: ) (GeV Q p+pb LHC (7 TeV+.75 TeV) Present nuclear DIS and Drell-Yan in p+a ppb@lhc y lab = 4 y lab = y lab = 0 ) (GeV Q nuclear DIS - F,A (x,q ) Proposed facilities: LHeC Fixed-target data: NMC E77 E139 E665 EMC epb@lhec e-pb (LHeC) (70 GeV -.75 TeV) Q sat,pb (x) y lab = 6 Present DIS+DY Q s (Pb, b=0 fm) x A perturbative non-perturbative ) (GeV Q 5 Ultra-peripheral QQ: LHC Υ ( y <.5) LHC J/Ψ ( y <.5) Q s (Pb, b=0 fm) perturbative non-perturbative Nuclear DIS & DY data: NMC (DIS) SLAC-E139 (DIS) FNAL-E665 (DIS) EMC (DIS) FNAL-E77 (DY) PbPb@LHC The LHeC will explore a region overlapping with the LHC: in a cleaner experimental setup; on firmer theoretical grounds x x Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 8

15 Contents: I. Motivation.. ea at the LHeC and comparison to the LHC. 3. Physics case in ea: Inclusive measurements and nuclear PDFs. Diffraction. Final states: dynamics of QCD radiation and hadronization. 4. Summary and outlook. CDR, arxiv: , J. Phys. G 39 (01) ; arxiv: ; arxiv:111.5; LHeC talks at DIS013 and LPCC Small-x in ea at the LHeC. 9

16 ea inclusive: comparison Good precision can be obtained for F(c,b) and FL at small x (Glauberized 3-5 flavor GBW model, NA 0). Not optimized! 1. R Pb F (x,5 GeV ) 1. R Pb F L (x,5 GeV ) EPS09 nds HKN07 DSSZ FGS AKST Data: LHeC EPS09 nds HKN07 FGS AKST Data: LHeC x x -1 Fc Pb Note the scale!!! Fb Pb Small-x in ea at the LHeC: 3. Physics case in ea.

17 Nuclear PDFs at small x: F data substantially reduce the uncertainties in DGLAP analysis; inclusion of charm, beauty (new!); and FL (new!) also give constraints. Small-x in ea at the LHeC: 3. Physics case in ea. 11

18 Nuclear PDFs at small x: F data substantially reduce the uncertainties in DGLAP analysis; inclusion of charm, beauty (new!); and FL (new!) also give constraints. Pb Pb Pb =1.69 GeV ) Valence EPS09NLO Fit 1 Sea Glue (, Pb Q =1.69 GeV F only =0 GeV ) EPS09NLO Fit (, Pb Q =0 GeV Small-x in ea at the LHeC: 3. Physics case in ea. 11

19 Nuclear PDFs at small x: F data substantially reduce the uncertainties in DGLAP analysis; inclusion of charm, beauty (new!); and FL (new!) also give constraints. Pb Pb Pb =1.69 GeV ) Valence F + Fc,b + FL EPS09NLO Fit 1 Sea Glue (, Pb Q =1.69 GeV F only =0 GeV ) (, Pb Q =0 GeV EPS09NLO Fit 1 F only Small-x in ea at the LHeC: 3. Physics case in ea. 11

20 Diffraction in ep and shadowing: e Diffraction is linked to nuclear shadowing through basic QFT (Gribov): ed to test and set the benchmark for new effects. Small-x in ea at the LHeC: 3. Physics case in ea. 1

21 Diffraction in ep and shadowing: e Diffraction is linked to nuclear shadowing through basic QFT (Gribov): ed to test and set the benchmark for new effects. Small-x in ea at the LHeC: 3. Physics case in ea. 1

22 Elastic VM production in ea: γ * A J/Ψ A For the coherent case, predictions available. coherent 1/A dσ/dt (µb/gev ).5 Saturation effects 1.5 Challenging experimental problem (neutron tagging in ZDC?). 1 incoherent Small-x in ea at the LHeC: 3. Physics case in ea. W (GeV) 13

23 Transverse scan: elastic VM t-differential measurements give a gluon tranverse mapping of the hadron/nucleus. Small-x in ea at the LHeC: 3. Physics case in ea. 14

24 Transverse scan: elastic VM t-differential measurements give a gluon tranverse mapping of the hadron/nucleus. Large extent in t with good precision. Sizable saturation effects expected. Small-x in ea at the LHeC: 3. Physics case in ea. 14

25 Dihadron azimuthal decorrelation: ΔΦ=Φ1 Dihadron azimuthal decorrelation: xa<<xp currently discussed at RHIC as suggestive of saturation. At the LHeC it could be studied far from the kinematical limits. Albacete-Marquet pt lead >3 GeV pt ass > GeV zlead=zass=0.3 y=0.7 Q =4 GeV Small-x in ea at the LHeC: 3. Physics case in ea. 15

26 Radiation and hadronization: LHeC: dynamics of QCD radiation and hadronization. Most relevant for particle production off nuclei and for QGP analysis in HIC. Low energy: hadronization inside formation time, (pre-)hadronic absorption,... ratio of FFs A/p High energy: partonic evolution altered in the nuclear medium. z=phadr/pparton hadron rest frame ν=estruck parton Small-x in ea at the LHeC: 3. Physics case in ea. 16

27 Radiation and hadronization: LHeC: dynamics of QCD radiation and hadronization. Most relevant for particle production off nuclei and for QGP analysis in HIC. Low energy: hadronization inside formation time, (pre-)hadronic absorption,... ratio of FFs A/p High energy: partonic evolution altered in the nuclear medium. z=phadr/pparton hadron rest frame ν=estruck parton Small-x in ea at the LHeC: 3. Physics case in ea. Fixed-target LHeC 16

28 Summary: At an High-precision tests of collinear factorization(s) and determination of PDFs. Unprecedented access to small x in p and A. Novel sensitivity to physics beyond standard pqcd. Stringent tests of QCD radiation and hadronization. Transverse scan of the hadron/nucleus at small x.... with implications on our understanding of QGP. The LHeC will answer the question of saturation/ non-linear dynamics. For that, ep AND ea essential!!! ln 1/x non-perturbative region BK/JIMWLK BFKL DENSE REGION DGLAP saturation scale Q s (x) DILUTE REGION ln 1/x ep DILUTE REGION ea [fixed Q] DENSE REGION ln QCD ln Q ln A Small-x in ea at the LHeC. 17

29 Outlook: With CERN and NuPECC mandate to further motivate the physics case and produce a TDR around 015, several items have to be done/improved: Refine DGLAP fits with flavour decomposition (include neutrino data, relax assumptions) and optimized FL scenarios, and LHC data. Monte Carlo generators!!! Studies on diffraction: separation of coherent from incoherent, ndpdfs, dijets,... Large x, EW bosons. Nuclear GPDs: nuclear DVCS etc. ed. Jet reconstruction, angular decorrelation Cooperation with EIC in some of these items desirable. Small-x in ea at the LHeC. Any collaboration is more than welcome!!! 18

30 Outlook: With CERN and NuPECC mandate to further motivate the physics case and produce a TDR around 015, several items have to be done/improved: Refine DGLAP fits with flavour decomposition (include neutrino data, relax assumptions) and optimized FL scenarios, and LHC data. Monte Carlo generators!!! Studies on diffraction: separation of coherent from incoherent, ndpdfs, dijets,... Large x, EW bosons. Nuclear GPDs: nuclear DVCS etc. ed. Jet reconstruction, angular decorrelation Thanks for your attention! Cooperation with EIC in some of these items desirable. Small-x in ea at the LHeC. Any collaboration is more than welcome!!! 18

31 Backup: Small-x in ea at the LHeC: Understanding the IS of URHIC. 19

32 Small x and saturation: xg A (x, Q s) R A Q s 1 = Q s A 1/3 x 0.3 QCD radiation of partons when x decreases leads to a large number of partons (gluons), provided each parton evolves independently (linearly, Δ[xg] xg). This independent evolution breaks at high densities (small x or high mass number A): non-linear effects (gg g, Δ[xg] xg - k(xg) ). Small-x in ea at the LHeC: 1. Motivation. 0

33 Small x and saturation: xg A (x, Q s) R A Q s 1 = Q s A 1/3 x 0.3 QCD radiation of partons when x decreases leads to a large number of partons (gluons), provided each parton evolves independently (linearly, Δ[xg] xg). This independent evolution breaks at high densities (small x or high mass number A): non-linear effects (gg g, Δ[xg] xg - k(xg) ). Small-x in ea at the LHeC: 1. Motivation. 0

34 Status of small-x physics: Three pqcd-based alternatives to describe small-x ep and ea data (differences at moderate Q (>Λ QCD) and small x): DGLAP evolution (fixed order perturbation theory). Resummation schemes: BFKL, CCFM, ABF, CCSS. Saturation (CGC, dipole models). Non-linear effects (unitarity constraints) are density effects: where? two-pronged approach at the LHeC: x / A. ln 1/x non-perturbative region BK/JIMWLK BFKL DENSE REGION DGLAP saturation scale Q s (x) DILUTE REGION ln 1/x ep DILUTE REGION ea [fixed Q] DENSE REGION ln QCD Small-x in ea at the LHeC: 1. Motivation. ln Q ln A 1

35 Kinematics: Q sat,gb Black: HERA 08 1/3 Q sat,gb Green:0+0 Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. Small-x demands 1 degree acceptance. Higher luminosity would benefit high-x and Q studies.

36 Kinematics: ) (GeV Q 6 5 nuclear DIS - F,A (x,q ) Proposed facilities: LHeC Fixed-target data: Q s perturbative NMC E77 E139 E665 EMC (Pb, b=0 fm) non-perturbative e-pb (LHeC) (70 GeV -.75 TeV) x Q sat,gb Black: HERA 08 1/3 Q sat,gb Green:0+0 Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. Small-x demands 1 degree acceptance. Higher luminosity would benefit high-x and Q studies.

37 LHC studies: PbPb: EW bosons. VMs in UPCs. Ridge.... ppb: Charged particles. Ridge. Flow. Back-to-back correlations, central-forward and forwardforward? EW bosons, DY? VMs, HF? UPCs? Jets and interjet activity?... Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 3

38 PbPb: EW bosons. VMs in UPCs. Ridge.... LHC studies: CMS, CMS, ppb: Charged particles. Ridge. Flow. Back-to-back correlations, central-forward and forwardforward? EW bosons, DY? VMs, HF? UPCs? Jets and interjet activity?... CMS, ATLAS, Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 3

39 LHC studies: PbPb: EW bosons. VMs in UPCs. Ridge.... ppb: Charged particles. Ridge. Flow. Back-to-back correlations, central-forward and forwardforward? EW bosons, DY? VMs, HF? UPCs? Jets and interjet activity?... ALICE, Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 3

40 LHC studies: PbPb: EW bosons. VMs in UPCs. Ridge.... ppb: Charged particles. Ridge. Flow. Back-to-back correlations, central-forward and forwardforward? EW bosons, DY? VMs, HF? UPCs? Jets and interjet activity?... CMS, ALICE, Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 3

41 LHC studies: PbPb: EW bosons. VMs in UPCs. Ridge.... ppb: Charged particles. Ridge. Flow. Back-to-back correlations, central-forward and forwardforward? EW bosons, DY? VMs, HF? UPCs? Jets and interjet activity?... ALICE, ALICE, Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 3

42 LHC studies: PbPb: EW bosons. VMs in UPCs. Ridge.... ppb: Charged particles. Ridge. Flow. Back-to-back correlations, central-forward and forwardforward? EW bosons, DY? VMs, HF? UPCs? Jets and interjet activity?... CMS, ALICE, ATLAS, Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 3

43 LHC studies: PbPb: EW bosons. VMs in UPCs. Ridge.... ATLAS, ppb: Charged particles. Ridge. Flow. Back-to-back correlations, central-forward and forwardforward? EW bosons, DY? VMs, HF? UPCs? Jets and interjet activity?... Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 3

44 LHC studies: PbPb: EW bosons. VMs in UPCs. Ridge.... ppb: Charged particles. Ridge. Flow. Back-to-back correlations, central-forward and forwardforward? EW bosons, DY? VMs, HF? UPCs? Jets and interjet activity?... ATLAS, The existence of collective effects in ppb is somewhat unexpected. Are they really final state? Do they exist also in ea? Small-x in ea at the LHeC:. ea at the LHeC and comparison to the LHC. 3

45 LHeC scenarios: For F I Ca 5-3? 5-3?? eca For FL:, 5, (7000); Q sx; Lumi=5,,0 pb -1 respectively; charm and beauty: same efficiencies in ep and ea. Small-x in ea at the LHeC: 3. Physics case in ea. 4

46 Note: FL in ea FL traces the nuclear effects on the glue (Cazarotto et al 08). Uncertainties in the extraction of F 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, Small-x in ea at the LHeC: 3. Physics case in ea. 5

47 Elastic VM production in ep: Elastic J/ψ production appears as a candidate to signal saturation effects at work!!! γ Linear, sensitivity to (xg). 1 z (1 z) r r E z x x b p p Non-linear, saturation. Small-x in ea at the LHeC: 3. Physics case in ea. 6

48 Diffractive DIS on nuclear targets: Challenging experimental problem, requires Monte Carlo simulation with detailed understanding of the x IP F D x IP = Q =3 GeV x IP = Q =3 GeV x IP = Q =30 GeV x IP =0.001 Q =3 GeV -3-1 x IP =0.001 Q =30 GeV - x IP =0.01 Q =3 GeV -3-1 x IP =0.01 Q =30 GeV - nuclear break-up. For the coherent case, x IP =0.001 Q =300 GeV x IP =0.01 Q =300 GeV - predictions available. Small-x in ea at the LHeC: 3. Physics case in ea H1 fit B ipsat bcgc -1 Pb -1-1 x IP =0.01 Q =3000 GeV β 7

49 Radiation and hadronization: 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). 5 o <θπ<5 o, xπ>0.01 formation time effects Daleo et al. 04 Data: H1 04 Small-x in ea at the LHeC: 3. Physics case in ea. 8

50 Radiation and hadronization: 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). dσ π /dx B (nb) Q 8 GeV MSTW-DSS (ep) Q 0 GeV MSTW-DSS (epb) nds-dss (epb) nds-nff (epb) EPS09-DSS (epb) dσ π /dp T (pb/gev) 1 MSTW-DSS MSTW-DSS (Pb) ndss-dss (Pb) nds-nff (Pb) EPS-DSS (Pb) Q 4.5 GeV Q 15 GeV Q 70 GeV 15 Q 70 GeV p T 3.5 GeV x Bj p T (GeV) Small-x in ea at the LHeC: 3. Physics case in ea. 8

51 Radiation and hadronization: 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). Small-x in ea at the LHeC: 3. Physics case in ea. 8

52 Jets: 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. Small-x in ea at the LHeC: 3. Physics case in ea. 9

53 Outlook: With CERN and NuPECC mandate to further motivate the physics case and produce a TDR around 015, several items have to be done/improved: Refine DGLAP fits with flavour decomposition (include neutrino data, relax assumptions) and optimized FL scenarios, and LHC data. Monte Carlo generators!!! Studies on diffraction: separation of coherent from incoherent, ndpdfs, dijets,... Large x, EW bosons. Nuclear GPDs: nuclear DVCS etc. ed. Jet reconstruction, angular decorrelation Cooperation with EIC in some of these items desirable. Small-x in ea at the LHeC. 30

54 Outlook: With CERN and NuPECC mandate to further motivate the physics case and produce a TDR around 015, NuPECC several items LRP have to be done/improved: Refine DGLAP fits with flavour decomposition (include neutrino data, relax assumptions) and optimized FL scenarios, and LHC data. Monte Carlo generators!!! Studies on diffraction: separation of coherent from incoherent, ndpdfs, dijets,... Large x, EW bosons. Nuclear GPDs: nuclear DVCS etc. ed. Jet reconstruction, angular decorrelation Cooperation with EIC in some of these items desirable. Small-x in ea at the LHeC. 30

55 Outlook: With CERN and NuPECC mandate to further motivate the physics case and produce a TDR around 015, several items have to be done/improved: Refine DGLAP fits with flavour decomposition (include neutrino data, relax assumptions) and optimized FL scenarios, and LHC data. Monte Carlo generators!!! Studies on diffraction: separation of coherent from incoherent, ndpdfs, dijets,... Large x, EW bosons. Nuclear GPDs: nuclear DVCS etc. ed. Jet reconstruction, angular decorrelation Cooperation with EIC in some of these items desirable. Small-x in ea at the LHeC. 30

56 Outlook: With CERN and NuPECC mandate to further motivate the physics case and produce a TDR around 015, several items have to be done/improved: Refine DGLAP fits with flavour decomposition (include neutrino data, relax assumptions) and optimized FL scenarios, and LHC data. Monte Carlo generators!!! Studies on diffraction: separation of coherent from incoherent, ndpdfs, dijets,... Large x, EW bosons. Nuclear GPDs: nuclear DVCS etc. ed. Jet reconstruction, angular decorrelation Thanks for your attention! Cooperation with EIC in some of these items desirable. Small-x in ea at the LHeC. 30