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17 March 2004Physics with Spin Historical Context It is now common wisdom that lepton scattering experiments are greatly enhanced by the availability of spin degrees of freedom Jefferson Laboratory was conceived (I was in undergraduate school), proposed and approved without polarized beam! - Beam and target spin greatly increase the scope of anticipated and unexpected results - Experimental technology is pushed in ways that benefit other subfields of science Fundamental spin physics experiments over the past 30 years have helped bring about a major change in attitude
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17 March 2004 Physics with Spin
Physics with SpinKrishna Kumar
University of Massachusetts
thanks to A. Deshpande, R. Ent, E. Hughes, X. Ji, N. Makins, Z-E. Meziani,and all parallel session speakers
The Second Electron-Ion Collider Workshop,Jefferson Laboratory
March 17, 2004
17 March 2004 Physics with Spin
Outline
• Introduction• Parallel Session Program• Inclusive Scattering• Semi-inclusive scattering• Exclusive scattering• Summary
17 March 2004 Physics with Spin
Historical ContextIt is now common wisdom that lepton scattering experiments are greatly enhanced by the availability of spin degrees of freedom
Jefferson Laboratory was conceived (I was in undergraduate school), proposed and approved without polarized beam!
- Beam and target spin greatly increase the scope of anticipated and unexpected results- Experimental technology is pushed in ways that benefit other subfields of science
Fundamental spin physics experiments over the past 30 years have helped bring about a major change in attitude
17 March 2004 Physics with Spin
Spin and the EIC
•High electron longitudinal beam polarization•High light ion beam polarization (longitudinal and transverse)•High luminosity•High Center of Mass Energy•Positron Beam (high luminosity for GPDs?!)
Giant strides in the production of intense, highly polarized electron and ion beams
17 March 2004 Physics with Spin
Parallel Session Overview
• Spin (I)– Inclusive measurements and Gluon spin
• Transversity– Polarized Semi-Inclusive measurements
• Spin (II)– Using Spin for Flavor Separation
• Angular Momentum– Quark Spatial Distributions and GPDs
17 March 2004 Physics with Spin
Parallel Sessions (I)Monday, March 15, 2004 - VARC 53/55
Spin (I) - Chair: Oscar Rondon (UVa)14:00 - 14:15 The g1 Structure Function at Low x - Introduction Werner Vogelsang14:15 - 14:45 Measurement of g1 at the Future Collider and G
from pQCD Evolution of the Structure Function Ernst Sichtermann14:45 - 15:15 Open Charm Production at Colliders Antje Bruell15:15 - 15:45 The Photon Content of Unpolarized and Polarized
Nucleons Asmita Mukherjee15:45 - 16:00 Electroweak and SM Physics at EIC Rolf Ent16:00 - 16:20 Coffee Break
Transversity - Chair: Zein-Eddine Meziani (Temple)16:20 - 16:45 Azimuthal Spin Asymmetries for the Large pt Hadron
Production at eRHIC Yuji Koike16:45 - 17:10 Transversity Measurements at Colliders Naomi Makins17:10 - 17:35 SIDIS and Current Fragmentation Stefan Kretzer
17 March 2004 Physics with Spin
Parallel Session (II)Tuesday, March 16, 2004 - VARC 53/55
Spin (II) - Chair: Werner Vogelsang (BNL/RBRC)14:00 - 14:25 Polarized Semi-Inclusive Physics Measurements
at HERMES and Future Prospects at the Colliders Ed Kinney14:25 - 14:50 Polarized Photoproduction at ep Colliders Marco Stratmann14:50 - 15:15 Lambda and Hyperon Physics Naomi Makins15:15 - 15:40 Spatial Distributions of Quarks/Gluons in the Nucleon
at Large Nc Christian Weiss
Angular Momentum - Chair: Latifa Elouadrhiri (JLab)15:40 - 16:05 Quantum Phase-Space Tomography of Quarks
in the Proton Xiangdong Ji16:05 - 16:20 Coffee Break 16:20 - 16:45 Measurement of GPDs at JLab and Future Colliders Harut Avakian16:45 - 17:10 Generalized Parton Distributions at Large x Feng Yuan17:10 - 17:35 Detector Issues N. Smirnov17:35 - 18:00 GPDs and Color Transparency Phenomena Simonetta Liuti
17 March 2004 Physics with Spin
Inclusive DIS
Spin structure functions g1 and g2 describe the spin-dependent cross-sections
Sichtermann, Vogelsang
Precision measurements on 1H, 2H and 3He targets at CERN, DESY and SLAC
17 March 2004 Physics with Spin
Gluon Spin in the Nucleon
€
s = 12
= 12
ΔΣ + Lq + ΔG + LG
€
Σ=0.25 ± 0.1Gluon contribution is likely to be substantial:Profound implications for our basic understanding of the nucleon which must be directly measured by experiment
RHIC Spin and COMPASS experiments will provide the first precise measurements towards this goal
The gold standard: measure G from a variety of experiments, where the dominant theoretical input is NLO QCD and residual model dependence is negligible and non-controversial
17 March 2004 Physics with Spin
G from Q2 Evolution of g1Sichtermann
EIC expected improvement in statistical uncertainty on G with analyzed data with 100 pb-1:~3 5 on 250 GeV
~4 10 on 250 GeV~7 20 on 250 GeV
with respect to the present uncertainty of ~0.5
The dream is to produce a similar plot for xg(x) vs x
HERA
17 March 2004 Physics with Spin
Gluon Spin from Open CharmBruell
•Critical, complementary method to obtain G•Simulation work on open charm is just beginning•EIC should provide a clean, high statistics data sample
charm
charm
several stiff kaons in the central regions and a forward electron
17 March 2004 Physics with Spin
Polarized PhotoproductionMukherjee, Stratmann
High Energy Convergence of the GDH sum rule
Direct Photon Resolved Photon
Estimate for a 1 fb-1 data sample
sufficient resolution to tag photoproduction andmeasure jet 4-momentum
Asymmetry
17 March 2004 Physics with Spin
Spin Structure Summary
⎟⎟⎠⎞
⎜⎜⎝⎛
−−⎟⎟⎠⎞
⎜⎜⎝⎛
=−∫∫ ...)(161)()(
21
01
1
01 π
α Qggdxxgdxxg S
V
Anp
The final design parameters of the EIC must guarantee multiple, precision measurements of G
Should a high precision test of the Bjorken Sum Rule be pursued?
: requires a careful evaluation of systematics of polarimetry
New information on the polarized photon’s partonic content
What can be gained by precision studies of g2?
17 March 2004 Physics with Spin
Polarized Semi-Inclusive DISMakins, Kinney, Kretzer, Koike
Flavor separation of parton distribution functions and fragmentation functions via azimuthal single and double-spin asymmetries with tagged pions and kaons
17 March 2004 Physics with Spin
TransversityMakins
•transverse polarization introduces a new structure fn. h1•Cannot be accessed by inclusive scattering•Information on transverse quark distribution in the nucleon•The first moment of h1 yields the nucleon’s tensor charge
The most favorable spin configuration is an unpolarized beam on a transversely polarized target
While first measurements are being carried out at HERMES and new measurements will be carried out Jefferson Lab and spin RHIC, EIC will be a laboratory where transversity will be extracted with reduced theoretical uncertainty
17 March 2004 Physics with Spin
Tomography of the Nucleon• A framework to extract 3-D spatial information of quarks in a
nucleon at rest• Generate Wigner (quantum phase-space) distributions• Obtain proton images at fixed x• Direct connection to GPDs through Fourier Transforms
Ji
Ultimate strategy:•Data on various hard exclusive processes•Deconvolution and global fits to obtain GPDs•Further constraints from Lattice QCD•Obtain tomographic 3-D pictures of the nucleon•Understand origins of mass and spin structure
17 March 2004 Physics with Spin
Proton Images at Fixed x
x
y
z
Up-quark densitiesx=0.01
x=0.7x=0.4
Ji
17 March 2004 Physics with Spin
GPDsAvakian, Luiti, Weiss, Yuan
CLAS 5.7 GeV: DVCS SSA
•Resolution (especially t)•Acceptance•Luminosity•Kinematic coverage
EIC Issues(Deconvolution!)
•Can we set a gold standard? •Can moments of GPDs make contact with Lattice QCD?
17 March 2004 Physics with Spin
Detector IssuesN. Smirnov
AEROGEL
HCAL
P/Ae
EMCal
TOF
Outer trackers
Innertrackers
Beam elements
Solenoid
A HERA likeDetector with dedicated PID:>>Time of flight>>Aerogel Ckov
5m
(Not to scale)
Forward detectors including
Roman Pots etc…
AND
Example
17 March 2004 Physics with Spin
Parity Violation (I)Ent
Beyond the Standard ModelLeptoquarksRPV SUSY ExtensionsE6 Z’ Based Extensions
Due to finite Y
1035 /cm2/sSub 0.5% polarimetry
17 March 2004 Physics with Spin
Parity Violation (II)Tofirst order, there is no difference between fixed- target DIS and collider DIS for such a measurement
•y dependence, perhaps gain in systematics•More selective x range: better theory control
Why even bother after HERA measurements?
Any new physics signature can be characterized as a contact interaction at “low” energy
The goal of “low” energy experiments is to characterize all chiral combinations with all initial and final state fermions
The goal is NOT to find the first signature of new physics and go to Stockholm
The goal is to help our LHC colleagues, who are likely to be staring at a tantalizing, low statistics signal
17 March 2004 Physics with Spin
Parity Violation (III)The g5 structure function
• Experimental signature is a huge asymmetry in detector (neutrino)• Unique measurement• Unpolarized xF3 measurements at HERA in progress• Will access heavy quark distribution in polarized DIS
Worth doing even if no positron beam
17 March 2004 Physics with Spin
Parity Violation (wild)The partonic structure of the Z boson?
Suppose you had enough luminosity to see the PV Asymmetry at low Q2
Would one learn something new about the partonic content of the photon?What is the correct description to think about this process?
17 March 2004 Physics with Spin
Polarized Sources• Polarized electron sources (polarization
and intensity) are not a technical hurdle• Likely the same thing for proton sources• Some work on 2H at BNL• Precision inclusive physics requires
polarized 3He. This is a new technical challenge
17 March 2004 Physics with Spin
Polarimetry• Electron polarimetry at 0.5% likely
doable in 10 years• If sub-0.5% is required, this is a major,
independent effort– Beyond the Standard Model?
• Proton polarimetry will reach ~5% at the RHIC spin program– Bjorken sum rule test needs sub-5%?
• 2H and 3He polarimetry? We need to start thinking about this.
17 March 2004 Physics with Spin
Back to Physics…..• Inclusive DIS
– EIC is the ultimate gluon spin machine– Close the book on longitudinal spin structure
• Semi-Inclusive DIS– New window into spin structure– Transversity, flavor separation, fragmentation…..
• Exclusive DIS– Deconvolve experimental data to extract GPDs?– GPDs provide full description of the nucleon?– Conceptual understanding of nucleon structure?
• The focus should be to make as much contact with Lattice QCD as possible
17 March 2004 Physics with Spin
A Look Forward• RHIC spin and Jlab physics will push a
significant component of the required experimental technology
• We will also learn a whole lot about how to analyze EIC data while grappling with analysis issues at these facilities
• Key question: What is the optimum center of mass energy range and luminosity range?– You could make a strong case for 2
machines!– How many detectors should we plan for?
17 March 2004 Physics with Spin
Closing Thoughts• Phew! That was hard!• I learnt a lot! (Did you?)• We in this room know that there is an extraordinary
opportunity to further our understanding of the nucleon with an EIC
• To make headway on funding outside this room, we need to focus our combined efforts on bringing a coherent case to the rest of the science community
• Spin physics will play a critical role, both in strengthening the physics case and in communicating our field to the public
17 March 2004 Physics with Spin
Tomography of the NucleonJi
• Wigner operator
• Wigner distribution: “density” for quarks having position r and 4-momentum k (off-shell)
No known experiment can measure this!7-dimensional distribution