Deeply Virtual Compton Scattering DVCS at 6 GeV with polarized beam and polarized target using the C - PowerPoint PPT Presentation

Loading...

PPT – Deeply Virtual Compton Scattering DVCS at 6 GeV with polarized beam and polarized target using the C PowerPoint presentation | free to view - id: 1ba3f2-Mzc1M



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Deeply Virtual Compton Scattering DVCS at 6 GeV with polarized beam and polarized target using the C

Description:

epep? (DVCS) BSA CLAS 4.2 GeV Published PRL. CLAS 4.8- 5.75 GeV Preliminary ... epepe e- (DDVCS) BSA CLAS 5.75 GeV under analysis. GPD Reaction Obs. Expt Status. From ... – PowerPoint PPT presentation

Number of Views:80
Avg rating:3.0/5.0
Slides: 33
Provided by: julie97
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Deeply Virtual Compton Scattering DVCS at 6 GeV with polarized beam and polarized target using the C


1
Deeply Virtual Compton Scattering (DVCS) at 6
GeV with polarized beam and polarized target
using the CLAS detector

Latifa Elouadrhiri Jefferson Lab for the CLAS
Collaboration
2
DVCS at 6 GeV with polarized target and polarized
beam using the CLAS detector
  • H. Avakian, S. Boyarinov, V.D. Burkert, L.
    Elouadrhiri1,2, M. Ito, Y. Sharabian, E. Smith,
    S. Stepanyan
  • Jefferson Lab
  • J. Ball, P. Bertin, A. Camsonne, R. De Masi, F.
    Descamps, M. Garçon, F-X. Girod, M. Guidal, H-S.
    Jo,
  • M. Mazouz, M. Mac Cormick, B. Michel, C. Munoz
    Camacho, S. Niccolai1, F. Sabatie, E. Voutier
  • LPC (Clermont) / LPSC (Grenoble) / IPNO (Orsay)
    /SPhN (Saclay)
  • CEA /DSM/DAPNIA CNRS/IN2P3
  • K. Joo1, N. Markov, M. Ungaro, B. Aaho
  • University of Connecticut
  • A. Biselli1
  • Fairfield University
  • S. Kuleshov, O. Pogorelko, P. Shiskov Institute
    of Theoretical and Experimental Physics, Moscow
  • H. Aznauryan, N, Dashyan, K. Egiyan Yerevan
    Physics Institute
  • V. Koubarovsky, P. Stoler Rensselaer Polytechnic
    Institute M. Amarian, G. Dodge, H. Juengst,
    S.E. Kuhn, A. Radyushkin, L. Weinstein Old
    Dominion University M. Vanderhaeghen College of
    William and Mary
  • S. Chen
  • Florida State University

1Co-spokesperson 2Contact person
3
Deeply Virtual Compton Scattering (DVCS) with
CLAS Exclusive ep ? e'p ?


We propose to study the DVCS with
  • longitudinally polarized target
  • 6 GeV polarized electron beam
  • optimized CLAS configuration to
  • detect all 3 particles in the final state
  • DVCS is one of the key reactions to
  • determine the Generalized Parton
  • Distributions (GPDs) experimentally.
  • It is the simplest process that can be described
    in terms of GPDs.

4

GPDs Deeply Virtual Exclusive Processes
handbag mechanism
Deeply Virtual Compton Scattering (DVCS)
x
g
x longitudinal quark momentum fraction
xx
x-x
2x longitudinal momentum transfer
t
xB
x

2-xB
5
Beyond form factors and quark distributions
Generalized Parton Distributions (GPDs)
M. Burkardt, … Interpretation in impact parameter
space
Proton form factors, transverse charge current
densities
6

Link to DIS and Elastic Form Factors
7
Accessing GPDs Through DVCS
  • GPDs are universal, they can be
  • determined in any suitable process

Eo 11 GeV
Eo 6 GeV
Eo 4 GeV
DVCS
BH
BH
TBH given by elastic form factors TDVCS
determined by GPDs
DVCS
sUL (BH) Im(DVCS) sinf h.t.
BH-DVCS interference generates beam and target
asymmetries that carry the nucleon structure
information.
DVCS/BH comparable, allows asymmetry, cross
section measurements
8
Separating GPDs Through Polarization
Polarized beam, unpolarized target


DsLU sinfF1H x(F1F2)H kF2Edf
H, H, E
Kinematically suppressed
Unpolarized beam, longitudinal target


H, H
DsUL sinfF1Hx(F1F2)(H … df
Unpolarized beam, transverse target
H, E
DsUT sinfk(F2H F1E) ….. df
Global analysis of polarized and unpolarized data
needed for GPD separation
9
Status of GPDs Studies at Jefferson Lab
GPD Reaction Obs. Expt Status
ep?ep?
(DVCS) BSA CLAS 4.2 GeV Published PRL
CLAS 4.8- 5.75 GeV Preliminary (
s) Hall A 5.75 GeV Fall 04 CLAS 5.75
GeV Spring 05 ep?ep? (DVCS) TSA CLAS 5.65
GeV Preliminary e(n)?en? (DVCS) BSA Hall
A 5.75 GeV Fall 04 ed?ed? (DVCS) BSA
CLAS 5.4 GeV under analysis ep?epee- (DDVCS)
BSA CLAS 5.75 GeV under analysis
From ep ? epX
Dedicated set-up
Dedicated set-up
No other proposals at Jefferson Lab are available
for the study of the DVCS process with a
polarized target.
10
DVCS with Polarized Target, Experimental Situation
Experimental Studies with CLAS Data were
collected as a by-product during the Eg1 2000
run 5.75 GeV with NH3 longitudinally polarized
target, ltQ2gt 1.8 GeV2
HERMES Experiment Preliminary target spin
asymmetries have been shown by HERMES
Collaboration DIS2005 Workshop, Madison (2005)
11
Experimental Setup for the proposed
experiment
  • CLAS Detector
  • Nearly 4p acceptance
  • Large kinematical coverage
  • Detection of charged and neutral particles
  • Electron Beam
  • Energy 6 GeV
  • Polarization 75
  • Solid Target
  • Longitudinally polarized NH3 target
  • Polarization 75
  • 12C 15N target
  • Inner Calorimeter (IC)

High resolution calorimeter to detect photons at
small angles (4o to 15o)
12
Hall B Longitudinally Polarized Target
  • Dynamically polarized NH3
  • 5 Tesla magnetic field
  • dB/B 10-4
  • 1K LHe cooling bath
  • NH3 polarization75
  • 12C, 15N, and 4He targets to measure the
    dilution factor

13
Magnetic Shielding for Møller Electrons
without magnetic field
14
CLAS Setup for DVCS Experiments
SC Helmholtz magnet
Inner calorimeter (PbWO4)
424 crystals, 16 mm long, pointing geometry,
1.2 degree/crystal, APD readout
Calibration via p0??? s 7.5 MeV
?
Photon detection in IC and EC (view
from target)
M?? (GeV)
15
Kinematics and Acceptance with CLAS IC
  • DVCS studies require
  • high Q2
  • low t

The much improved acceptance for photon
detection, and the longer running time will
allow us to extend the kinematics range to higher
Q2, and to map out the xB and t dependence in
small bins
16
Target Spin Asymmetry f Dependence
6 GeV run with NH3 longitudinally polarized
target (CLAS IC) 60 days of beam time
  • CLAS eg1 (preliminary)
  • CLAS (eg1IC) projected

A dedicated CLAS experiment with longitudinally
polarized target will provide a statistically
significant measurement of the kinematical
dependences of the DVCS target SSA
17
Target Spin Asymmetry Q2 Dependence
18
Target Spin Asymmetry t- Dependence
Higher t values will also be measured. The
interpretation within the handbag formalism
needs to be clarified.
19
Target Spin Asymmetry t- Dependence
20
Target Spin Asymmetry x- Dependence
21
Target Spin Asymmetry Q2- Dependence
22
Beam Time Request
We request 60 days of beam time with polarized
beam (Pe gt 75) and polarized target (PT gt 75)
No special equipment is needed for this
experiment, a similar setup has been used in eg1,
the only new component is the Inner Calorimeter
(IC) - IC was used recently in the e1-DVCS
experiment - the combination of polarized target
and IC prototype was used earlier
in a successful test run in November 2003

This experiment will run concurrently with
PR-05-113 and has identical requirements for
beam and experimental equipment.
23
Summary
  • Studies of hard exclusive electroproduction of
    photons are underway at JLab, allowing access to
    the GPDs.
  • The proposed measurements with longitudinally
    polarized target and polarized beam with the CLAS
    detector, together with the Hall-A and Hall B
    DVCS programs, will contribute uniquely to
    exploratory measurements of DVCS as a means of
    accessing the GPDs.
  • This program will
  • greatly improve the precision of the DVCS data
    on target spin asymmetry giving access to the
    imaginary part of H
  • provide the first significant measurement of the
    double spin asymmetry probing the real part of
    H and H

24
(No Transcript)
25
DVCS eg1 Separating DVCS Photons from Polarized
Protons in NH3
Events from both p0 and unpolarized target
nucleons are suppressed

Geometry cut qgxlt 1o
26
DVCS MC separating DVCS photons

Angular cut most efficient in separating p0
27
CLASInner Calorimeter (IC)
424 PbWO4 ……..crystals
IC
IC sE/E0.0034/E0.038/vE0.022
CLASIC
CLAS
Reconstruction efficiency of high energy p0 with
IC increases 4 times due to small angle coverage
CLAS
IC at CLAS opens new avenue for studies of spin
and azimuthal asymmetries in hard exclusive
processes g, p0,h,r
28
DVCS with a polarized target New CLAS experiment

DsLL cosfReF1Hx(F1F2)(H xE/2)..
5.7 GeV run with NH3 longitudinally polarized
targetIC
Projections for 60 days
The double spin asymmetry in DVCS with
longitudinally polarized target will provide
access to the real part of Compton form factors
29
GPD and DVCS
(at leading order)
Beam or target spin asymmetry contain only
ImT, therefore GPDs at x x and -x
Cross-section measurement and beam charge
asymmetry (ReT) integrate GPDs over x
(M. Vanderhaeghen)
30
D.E.S. an experimental challenge
Missing mass MX2
  • Resolution
  • Exclusivity
  • Luminosity
  • High transfers

ep ? epX MAMI 850 MeV
ep ? epX Hall A 4 GeV
Accessible kinematical domain
p0
?
ep ? epX CLAS 4.2 GeV
Np
N
ep ? e?X HERMES 28 GeV
(? ?)
31
Projected results (sample)
Dependence of j asymmetry and total cross-section
as a function of xB, t, Q2 , j (372 bins)
E01-113 V. Burkert, L. Edouardrihi, M. Garçon, S.
Stepanyan et al. Run March-May
2005
32
CLAS/DVCS (ep ? epX) at 5.75 GeV
H. Avakian L. Elouadrhiri
PRELIMINARY
PRELIMINARY
0.15 lt xBlt 0.4 1.50 lt Q2 lt 4.5 GeV2 -t lt 0.5 GeV2
GPD based predictions (Vanderhaeghen)
p0 are suppressed due to analysis cuts (only low
t), residual contribution (p/? 5-15) estimated
from MC
About PowerShow.com