the lhec project: deep inelastic scattering with e e =70gev and e p =7tev
DESCRIPTION
The LHeC Project: Deep Inelastic Scattering with E e =70GeV and E p =7TeV. P.Newman, Birmingham … with … J. Dainton, M. Klein, E. Perez, F. Willeke. Context of LHeC Physics Motivation Machine Considerations. hep-ex/0603016, Submitted to JINST. ee. ep. pp. - PowerPoint PPT PresentationTRANSCRIPT
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The LHeC Project: The LHeC Project: Deep Inelastic Deep Inelastic Scattering withScattering withEEee=70GeV and =70GeV and
EEpp=7TeV =7TeV
P.Newman, Birmingham
… with …
J. Dainton, M. Klein,E. Perez, F. Willeke
hep-ex/0603016,Submitted to JINST.
• Context of LHeC• Physics Motivation• Machine Considerations
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Historical Development Historical Development of Particleof Particle
Physics always Physics always involved ep involved ep interactions interactions
together with pp and together with pp and ee++ee--
DIS Bjorken scaling – QPM (high) parton densities neutral currents low x and diffraction asymptotic freedom …. QCD
e+e- J/Ψ 3 neutrinos … ILC gluons ….. electroweak theory pp charm, W,Z, bottom top LHC …
1970 2000 2015
?
ee
pp
ep
No agreed high energy ep programme after mid 2007!
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LHeC ContextLHeC Context
?!?
• Combining the LHC protonswith an electron beam isnatural next step in pushingthe frontiers of ep physics:small resolved dimensions, high Q2 and low x • Can be done without affecting pp running
Latest of several proposals totake ep physics into the TeV energy range …… but with unprecedented lumi! N
ucl
eon
Quark
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Inclusive KinematicsInclusive Kinematics
s 1.4 V Te
710 at x 1.4 eV TW
70 GeV eE 7 TeVpE
1.4 TeVeqM 2 6 22 10 GeV Q
2 2 1 GeVQ
High Q2 Frontier
Low x Frontier
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Overview of Physics MotivationsOverview of Physics Motivations-New Physics in the eq Sector leptoquarks, RP violating SUSY, quark compositeness
-The Low x Limit of Quantum Chromodynamics high parton densities with low coupling parton saturation, new evolution dynamics
-Quark-Gluon Dynamics and the Origin of Mass confinement and diffraction
-Precision Proton Structure for the LHC essential to know the initial state precisely! including heavy flavour (b), gluon
-Nuclear Parton Densities eA with AA -> partons in nuclei, Quark Gluon Plasma
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Lepton-quark Bound Lepton-quark Bound StatesStates
Yukawa coupling,
• Leptoquarks appear in many extensions to SM… explain apparent symmetry between lepton and quark sectors.
• Scalar or Vector color triplet bosons carryingL, B and fractional Q, complex structures likely!
• (Mostly) pair produced in pp, single production in ep.
• LHC sensitivity (to ~2TeV) extends beyond LHeC, but difficult to determine quantum numbers / spectroscopy!
LHC pair prod
(A.Zarnecki)
LHeC
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Leptoquark PropertiesLeptoquark Properties
e,
q
+F = -1
F = +1
e+
e-
q or q ?_
q or q ?_
MLQ (GeV)
Asy
mm
etr
y
LHeC: 10 fb-1 per charge
LHC: single prod. 100 fb-1
= 0.1
LHC: - Hard to determine quantum numbers from pair production. - Single production cross sections tiny.
LHeC: - Resonant production at high x implies q rather than qbar. Sign of e+p / e-p asymmetrythus determines fermion number F- Disentangle scalar / vector from angular distributions.- Disentangle chiral couplings by varying beam polarisation
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Inclusive Cross SectionsInclusive Cross Sections
200pb-1
1fb-1
• LHeC is a genuine electroweakcollider … exploit helicity andW exchange for quark flavour and q / qbar decomposition.
• It provides high NC and CC rates up to large values of x, for e.g. d/u determination
x
Reduce
d C
C x
-sect
ion
Q2 = 20000 GeV2R
educe
d N
C x
-sect
ion
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Example Proton Structure Constraint: Example Proton Structure Constraint: xGxG33
10 fb-1 per charge
Extracted from e+p / e-p NC cross section asymmetry … exampledata from HERA
3 ~ ( ) ( )u u d dxG a e u u a e d d
Improved precision andextension to lower x at LHeC
Tests symmetry of q and qbar in sea and / or measures valence density at very low x
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Heavy Flavour Constraints for LHCHeavy Flavour Constraints for LHC
• At Q2 values of LHC and LHeC, charm and beauty important
• Crucial for understanding initial state of many new processes (e.g. bbbar->H) and background rates.
• Precise knowledge available from ep …
F2b
fromH1 Si
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Strong Coupling Strong Coupling Constant Constant
2006 @ 10-9
2006 GF @ 10-5
2006 G @ 0.02%
2006 S @ 1-2%
LHeC s few/mil
• Improved precision at the LHeC due to increased lever arm in x and Q2, < 1% experimental precision and NNLO theory
• Unification?… s precision limits extrapolations to GUT scale
(Allanach et al, MSSM)
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Low x PhysicsLow x Physics • HERA `discovered’rise of F2 towardslow x … high partondensity, low couplinglimit of QCD …but many questions left unanswered…
• Parton saturation?
• Non-DGLAPevolution dynamics?
• Diffraction?
… LHeC at x < 10-6!
?
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Example: DiffractionExample: Diffraction• Diffractive DIS `discovered’ at HERA(~10% of events are ep -> eXp)
• Parton-level mechanism and relation to diffractive pp scattering, inclusive DIS, confinement still not settled
• Factorisable diffractive parton densities (DPDFs) work well in describing diffractive DIS at HERA
• At LHeC, DPDFs and theoreticalmodels can be tested in detail and possibly contribute to discoverypotential
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LHeC Diffractive KinematicsLHeC Diffractive Kinematics
• Factorisation tests / gluon: DPDFs extracted at HERA data predict LHeC cross section at moderate /large , higher Q2.• New dynamics: LHeC opens new low region – partonsaturation, BFKL etc showing up first in diffraction?•Large Diff. Masses: Z production, studies of new 1-- states•GPDs: Massive extension in x, W ranges for VMs, DVCS
DGLAP
(xIP<0.05)
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With AA at LHC, LHeC is also an eA With AA at LHC, LHeC is also an eA ColliderCollider
• LHeC extends by 4 orders Of magnitude towards lower x.
• With wide range of x, Q2, A, opportunity to extract andunderstand nuclear parton densities in detail
• Symbiosis with ALICE, RHIC, eRHIC … disentangling Quark Gluon Plasma from shadowing or parton saturation effects
• Rich physics ofnuclear parton densities.
• Limited x and Q2
range so far
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LHeC Basic PrincipleLHeC Basic Principle• On timescale of LHC upgrades
• ep in parallel with standard pp operation
• Proton beam parameters fixed by LHC
• 70 GeV electron beam, compromisingbetween energy and synchrotron (0.7 GeV loss per turn)
Superconducting RF cavities then consume 50MW for Ie=70mA
New detector possibly replaces LHCb at end of their programme?
Electron beam by-passes other experiments via existing survey tunnels
e
p
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Interaction RegionInteraction Region
Top view
2 mrad
Non-colliding p beamVertically displaced
• Matching electron and protonbeam shapes and sizes determines* x emittance for electron beam
• High luminosity requires low quadrupoles close to interactionpoint (1.2 m)
• Fast separation of beams withtolerable synchrotron power requires finite crossing angle
• 2 mrad angle gives 8 separation atfirst parasitic crossing
• Resulting loss of luminosity (factor 3.5)partially compensated by “crab cavities” … -> 1033 cm-2 s-1
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Overview of LHeC ParametersOverview of LHeC Parameters
e accelerator similar to LEP … FODO structure with 376 cells @ 60m (LEP 290 cells)
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Detector ConsiderationsDetector Considerations
Magnet free space of 1.2 m -> detector acceptance to 10o
• Considerably more asymmetric than HERA!
• Study of low x / Q2 and of energy flow in outgoingproton direction require more (1o) … but luminosity less important, so dedicated alternative set-up possible?
• Diffractive Proton (and neutron) tagging should be integral to design
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SummarySummaryLHC is a totally new world of energy and luminosity! LHeCproposal aims to exploit this for lepton-hadron scattering
New discoveries expected at LHC … interpretation may require ep, eA in comparable energy range
LHeC naturally extends low x and high Q2 frontiers of ep physics … new precision in our understanding of QCD
First conceptual design exists … no show-stopper so far
Much more to be done to fully evaluate physics potentialand determine optimum running scenarios!
Tentative plan to hold a workshop (October 26-28?) All invited to think about the possibilities and / or contribute!