QCD at energy frontier: From HERA to LHeC

1. antiprotons protons QCD at energy frontier:From HERA to LHeC protons electrons? protons Katsuo Tokushuku (KEK)

2. nuclei proton Deep Inelastic Scattering Philosophical Magazine, volume 21 (1911), pages 669-688 HERA: (27.5 GeVevs920GeVp) LHeC (60GeV e vs 7000GeV p and eA !) No sub-parton structure down to 0.63x10-18m (HERA-I/II result, prelim.) LHeC

3. LHeC History • Initial thoughts: Already from the bigginng of LHC planning for example ECFA-WS in 1987, Aachen WS in 1990. • “Deep Inelastic Electron-Nucleon Scattering at the LHC” J.B. Dainton, M. Klein, P. Newman, E. Perez, F. Willeke JINST 1 (2006) P10001 • 2006 Advisory Committee • 2007October: First meeting of Steering group • 2008-2010 : Extensive discussions in the ‘Divonne’ workshops with supports from CERN/ECFA/NuPECC • 2011 August: A draft CDR is ready! The reviewing process has started. http://cdsweb.cern.ch/record/1373421 527 pages! See http://cern.ch/lhec The official submission of the CDR is the real start.

4. How Could ep be Done using LHC? LHC Time Schedule (Not yet official) The only option is simultaneous ep and pp runing after 2022

5. How Could ep be Done using LHC? RING-RING LINAC-RING • First considered (as LEPxLHC) • in 1984 ECFA workshop • Main advantage: high peak • lumi obtainable (~2.1033 cm-2 s-1) • Main difficulties: building • round existing LHC, e beam • energy (~60GeV) and lifetime • limited by synchrotron radiation • Previously considered as `QCD • explorer’ (also THERA) • Main advantages: low interference • with LHC, high Ee ( 150 GeV?) and • lepton polarisation, LC relation • Main difficulties: lower luminosity • <1033 cm-2 s-1? at reasonable • power, no previous experience exists Both options are kept in CDR ⇒　Decision will be made in the future stage.

6. Challenge: Bypassing the main LHC detectors Bypassing CMS: 20m distance to Cavern IP2 Bypassing ATLAS: 100m wo survey gallery The LHeC Ring-Ring Challenging: bypassing the main LHC Detectors e-injector is a 10 GeV sc linac in triple racetrack configuration By-passes of existing experiments containing RF 6

7. The LHeC Ring-Ring Installation 1m above LHC and 60cm inside Challenging, but no show stopper yet

8. Magnets for Electron Ring (CERN, Novisibirsk) 3040 bending dipole magnets 5m long (35cm)2 transverse 0.013-0.08 T Compact and light ~200kg/m 736 arc quadrupole magnets First prototypes [1.2m long]

9. LR LHeC: recirculating* linac with e∓ energy recovery, or straight linac IP2 *) bypassing own IP The LHeC Linac-Ring

10. Accelerator Design in Linac-Ring Configuration • 4 separate designs • for 60 GeV electron • beam (CERN, Jlab, BNL) • 500 MeV injection • Two 10 GeV linacs, • 3 returns • Energy recovery in • same structures (94%)? More ambitious: Pulsed single 140 GeV Linac 31.5 MV/m (ILC)

11. Design Parameter Summary RR= Ring – Ring LR =Linac –Ring Include deuterons (new) and lead (exists) 10 fb-1 per year looks possible 1/5 of CLIC power. c.f. LHC : 140MW

12. LHeC Tentative Time Schedule LS3 --- HL LHC

13. Physics Programs at LHeC • √s = 1.3 TeV • Q2max =1.68TeV2 • xmin ~ 6x10-7 • at Q2 =1GeV2 New physics, distance scales few . 10-20 m Large x partons IntL =100 fb-1 High Statistics c.f. HERA~0.5fb-1/exp High precision partons in LHC plateau Low x parton dynamics • High mass • (Q2) frontier • Q2 lever-arm • at moderate x • Low x (high W) • frontier High Density Matter

14. Physics Programs at LHeC • √s = 1.3 TeV • Q2max =1.68TeV2 • xmin ~ 6x10-7 • at Q2 =1GeV2 IntL =100 fb-1 High Statistics c.f. HERA~0.5fb-1/exp xmin ~ 6x10-3 at Q2 =10000GeV2 : i.e. x=10-3 region can be probed with W,Z xmin ~ 6x10-7 at Q2 =1GeV2 : 10 times lower-x reach than HERA

15. NEW PHYSICS The LHeC will be operational after the LHC collects (at least) 300fb-1 data.

16. LHC: No new physics yet! １TeV

17. Lepton-quark Resonances • Leptoquarks appear in many extensions • to SM… explain apparent symmetry • between lepton and quark sectors. • Scalar or Vector color triplet bosons Carrying L, B and fractional Q, complex spectroscopy? • (Mostly) pair produced in pp, • single production in ep. • LHeC discovery potential for • masses <1.0 - 1.5 TeV for 10 fb-1 • – Comparable to LHC, • but cleaner final states • -> We can study its properties. Yukawa coupling, l (10 fb-1) LHC pair prod LHeC

18. _ e, _ q or q ? q e+ q or q ? e- Determining Leptoquark Quantum Numbers • Single production gives access • to quantum numbers: • fermion number (below) • spin (decay angular distributions) • chiral couplings (beam lepton polarisation asymmetry)

19. Sizeable CC (WW) x-section  Few1000 events / year before cuts Strongly dependent on mH Higgs  bbbar Coupling • Novel production mechanism • Clean signal: H + j + ptmiss • First study with 2 b-tags • Backgrounds (jets in NC, CC, • top) suppressed with cuts on • jet multiplicity, total Et, event • kinematics, missing pt • ~ 100 events / year after cuts?

20. PARTON DENSITY

21. k’ k e 27.5GeV Q2 g q p 920GeV x remnant jet p p W current jet Introduction: Deep Inelastic Scattering Described by 2 kinematic variables photon virtuality Bjorken x Inelasticity Q2=-q2 x = Q2/2p.q y = p.q/p.k s=Q2xy FL : Longitudinal Str. Ft. (0 in QPM) F3 : Small at Q2 << Mz2 quark distribution function

22. Parton densities of • proton in a large x range • Some limitations: • Insufficient lumi • for high x precision • Assumptions on quark • Flavour decomposition • No deuterons … • u and d not separated • No heavy ions HERA’s greatest legacy • H1/ZEUS/joint publications • Further progress requires higher energy and luminosity -> LHeC

23. Extended to Higher-Q2 LHeC

24. Gluon: now then Precision measurement of gluon density to extreme x – αs Low x: saturation? radical change of understanding High x: xg and valence quarks most crucial for new states Gluon in Pomeron, odderon, photon, nuclei.. Local spots in p? Heavy quarks intrinsic or only gluonic

25. 2 ee e γ eq q ve,ae e Z q vq,aq In SM, parity + parity - e ν W q q’

26. Measurement of q-Z coupling u-quark d-quark • Polarized data improves the vector couplings. • HERA-II data makes a significant impact on the u-quark couplings

27. Measurement of q-Z coupling u-quark d-quark • LHeC will significatcantly improve the measurements

28. Another example : xF3γZ Quark-charge weighted valence quark distribution cf. np: F3 : valence quark ep :F2 : charge-square weighted In SM,

29. Heavy Quarks bottom High precision c, b measurements (modern Si trackers, beam spot 15 * 35 m2 , increased rates at larger scales). Systematics at 10% level beauty is a low x observable! s (& sbar) from charged current xmin ~ 6x10-3 at Q2 =(Mw GeV)2 LHeC 10o acceptance LHeC 1o acceptance strange • (Assumes 1 fb-1 and • 50% beauty, 10% • charm efficiency • 1% uds  c • mistag probability. • 10% c  b mistag)

30. High precision measurements : Keys to the future

31. Low-x

32. What have we learned from HERA? Rapid rise of F2 can be explained will with pQCD for Q2 > a few GeV2

33. Study of lower-x with LHeC LHeC delivers a 2-pronged approach: 1) Probing lower x at fixed Q2 in ep [evolution of a single source] xminLHeC ~ 0.1 xminHERA 2) Increasing target matter in eA [overlapping many sources at fixed kinematics … density ~ A1/3 ~ 6 for Pb … worth 2 orders of magnitude in x]

34. Detector requirements: Challenging Q2 ~ 100 GeV2　→　θe=170° Q2 ~ 1 GeV2　→　θe=179°! : Electron scattered angle is very low. At Low-x hadrons are also going backward θhad=90-179° θhad=170° θhad=90° θe=170° θe=179°

35. Interaction Region RR -Small crossing angle ~1mrad (25ns) to avoid first parasitic crossing (L x 0.77) LR – Head on collisions, dipole in detector to separate beams Synchrotron radiation –direct and back, absorption simulated (GEANT4) .. Note that the LHeC has 4 beam lines near the IP :for electrons, protons, non-colliding protons and synchrotron photons [July 2010] 1st sc half quad (focus and deflect) separation 5cm, g=127T/m, MQY cables, 4600 A 2nd quad: 3 beams in horizontal plane separation 8.5cm, MQY cables, 7600 A

36. Requirements High Precision (resolution, calibration, low noise, tagging of b,c) Modular for ‘fast’ installation State of the art technology - ‘no’ R+D (HERA,LHC upgrade) 1-179o acceptance for low Q2, high x (beam pipe, synrad) Si tracker, LAr elm cal, sc coil 3.5T, Tile hcal, Muon detector not shown Present dimensions: LxD =14x9m2 [CMS 21 x 15m2 , ATLAS 45 x 25 m2] Taggers at -62m (e),100m (γ,LR), -22.4m (γ,RR), +100m (n), +420m (p)

37. Summary HERA has been exploring the structure of the proton and QCD dynamics at the highest precisions. Yet, still many un-answered questions are left: e.g. saturation at low-x, flavour compositions of the proton. The LHeC is the successor of HERA toward the energy frontier and luminosity frontier in ep (and eA) collisions. Simultaneous running of LHC and LHeC appears feasible and important to complement the LHC physics. LHeC CDR is being circulated among the referees and is already open. It will be finalized in 2012 after cooperating referee’s comments.

38. BACK UP

39. Scientific Advisory Committee Working Group Convenors Steering Committee CERN Referees LHeC Organisation

40. Ring-Ring • Power Limit of 100 MW wall plug • “ultimate” LHC proton beam • 60 GeV e± beam • L = 2 1033 cm-2s-1  O(100) fb-1 Two Options LINAC Ring Pulsed, 60 GeV: ~1032 High luminosity: Energy recovery: P=P0/(1-η) β*=0.1m [5 times smaller than LHC by reduced l*, only one p squeezed and IR quads as for HL-LHC] L = 1033 cm-2s-1  O(100) fb-1 Synchronous ep and pp operation (small ep tuneshifts) The LHC p beams provide 100 times HERA’s luminosity

41. http://cern.ch/lhec Thanks to all and to CERN, ECFA, NuPECC About 150 Experimentalists and Theorists from 50 Institutes Tentative list