General Kinematics for Polarized e Scattering on Polarized ... - blast

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U. Kentucky, 31 March 2005

BLAST: A Detector for Internal Target
Experiments



Introduction




Overview and status of the Program



Present Results



Outlook

John Calarco, UNH and UT

U. Kentucky, 31 March 2005

U. Kentucky, 31 March 2005

BLAST COLLABORATION



R. Alarcon,
E. Geis
, J. Prince, B. Tonguc, A. Young

Arizona State University, Tempe, AZ 85287



J. Althouse, C. D

Andrea, A. Goodhue, J. Pavel, T. Smith,

Dartmouth College, Dartmouth, NH



D. Dutta, H. Gao, W. Xu

Duke University

Durham, NC 27708
-
0305


H. Arenh
ö
vel,

Johannes Gutenberg
-
Universit
ä
t, Mainz, Germany



T. Akdogan, W. Bertozzi, T. Botto, M. Chtangeev,
B. Clasie
,
C. Crawford
,

A. Degrush
, K. Dow, M. Farkhondeh, W. Franklin, S. Gilad, D. Hasell, E. Ilhoff, J. Kelsey,

M. Kohl, H. Kolster,
A. Maschinot
, J. Matthews,
N. Meitanis
, R. Milner, R. Redwine,

J. Seely
, S. Sobczynski, C. Tschalaer, E. Tsentalovich, W. Turchinetz,
Y. Xiao
,
C. Zhang
,
V. Ziskin
, T. Zwart

Massachusetts Institute of Technology, Cambridge, MA 02139


and

Bates Linear Accelerator Center, Middleton, MA 01949



J. Calarco, W. Hersman, M. Holtrop,
O. Filoti
,
P. Karpius
,
A. Sindile
, T. Lee

University of New Hampshire, Durham, NH 03824




J. Rapaport

Ohio University, Athens, OH 45701



K. McIlhany, A. Mosser

United States Naval Academy, Annapolis, MD 21402



J. F. J. van den Brand, H. J. Bulten, H. R. Poolman

Vrije Universitaet and NIKHEF, Amsterdam, The Netherlands



W. Haeberli, T. Wise

University of Wisconsin, Madison, WI 53706










U. Kentucky, 31 March 2005



Approved BLAST Scientific Program



Form Factor Measurements: Q
2


1.0 (GeV/c)
2




Proton Charge and Magnetism

Elastic Scattering with Polarized Beam and
H

Target (
01
-
01
)

Neutron Charge and Magnetism and Deuteron Electromagnetic Structure

Quasi
-
elastic Scattering with Polarized Beam and
D
Target (
89
-
12

and
91
-
09
)


Elastic scattering off Tensor and Vector Polarized Deuterium (
00
-
03


and 03
-
02
)




U. Kentucky, 31 March 2005

General Kinematics for Polarized
e

Scattering
on a Polarized Target

U. Kentucky, 31 March 2005

Bates Linac




500MeV Linac recirculated to reach up to 1GeV



Inject into South Hall Ring



Polarization maintained by Siberian snakes



Polarization monitored real time by Compton Polarimeter



Internal Target located in the ring vacuum

U. Kentucky, 31 March 2005


Left
-
right symmetric detector


simultaneous parallel and
perpendicular asymmetry
determination


Large acceptance


covers 0.1GeV
2

≤ Q
2

≤ 1GeV
2


out
-
of
-
plane measurements



DRIFT CHAMBERS


momentum determination,
particle identification


CERENKOV COUNTERS


electron/pion discrimination


SCINTILLATORS


TOF, particle identification


NEUTRON COUNTERS


neutron determination


MAGNETIC COILS


3.8kG toroidal field


The
BLAST

Spectrometer

DRIFT CHAMBERS

CERENKOV

COUNTERS

SCINTILLATORS

NEUTRON COUNTERS

TARGET

BEAM

BEAM

U. Kentucky, 31 March 2005

BLAST: Present Configuration


U. Kentucky, 31 March 2005

Detector Performance


All detectors operating at or near designed level


Drift chambers
~98%

efficient per wire


TOF resolution of
300ps


Clean event selection


Cerenkov counters
85%

efficient in
electron/pion discrimination


Neutron counters
10%

(
25
-
30%
) efficient in
left (right) sectors


To be improved further


Reconstruction resolutions good but still being
improved




current

goal


p

3%

2%




0.5
°

0.3
°




0.5
°

0.5º


z

1cm

1cm

U. Kentucky, 31 March 2005


U. Kentucky, 31 March 2005

ep

Elastic Kinematic Correlation


U. Kentucky, 31 March 2005

Asymmetries
A
L

and
A
R

U. Kentucky, 31 March 2005

m
G
E
/G
M

from
ep

Elastic

U. Kentucky, 31 March 2005

m
G
E
/G
M

Comparison between BLAST and JLab

U. Kentucky, 31 March 2005

Inclusive
H(e,e’)

Cross Sections

TL
,

TT

from MC

U. Kentucky, 31 March 2005

Inclusive
H(e,e’)

Cross Sections from Data

U. Kentucky, 31 March 2005

Motivation I: Why Deuteron



N
-
N Interaction



Deuteron as test
-
bed for N
-
N interaction models


THE

2
-
nucleon bound state



D
-
wave admixture


Tensor force


Model predictions vary from 4% to 7%



Deuteron as neutron target


understand Deuteron structure

U. Kentucky, 31 March 2005


Loosely
-
bound deuterium readily breaks up


electromagnetically into two nucleons


e + d


e’ + p + n


Most generally, the cross section


can be written as


:


In the Born approximation,



vanishes in the L = 0 model for the deuteron (i.e. no L = 2 admixture)


Measure of L = 2 contribution and thus tensor NN component



Reaction mechanism effects (MEC, IC, RC) convoluted with tensor contribution


“There is no direct measure of the tensor component.”
--

somebody



provides a measure of reaction mechanisms


Useful for extraction of G
n
e


Beam
-
vector dilution (h•Pz) gotten from analysis


Deuteron Electrodisintegration


S
h,
P
z
,
P
zz



S
0
1

P
z
A
d
V

P
zz
A
d
T

h
A
e

P
z
A
ed
V

P
zz
A
ed
T





A
e

A
d
V

A
ed
T

0
T
d
A

A
ed
V
N)N
e'
,
e
(
d


U. Kentucky, 31 March 2005

Beam and Target Performance


Beam fills to
175mA
with
25min
lifetime, average polarization =
65%
±

4%


Deuterium polarization in tri
-
state mode


(Vector, Tensor) :



(
-
P
z
, +P
zz
) ( +P
z
, +P
zz
)



(0,
-
2P
zz
)


Flow = 2.2


10
16

atoms/s, Density = 6.0


10
13
atoms/cm
2


Luminosity = 4.0


10
31

/cm
2
/s @ 140mA


Target polarizations from data analysis: P
z

=
88%
±

4%
, P
zz

=
65%
±

2%

U. Kentucky, 31 March 2005

Motivation II: Why T
20



e
-
d elastic scattering: G
C

G
M

G
Q


G
Q


>

D
-
state
>

Tensor Force



Rosenbluth Separation







3
rd

Measurement to separate 3 form factors






Tensor Asymmetry in e
-
d elastic scattering



U. Kentucky, 31 March 2005


e
-
d Elastic Event Selection



Timing Cuts



Coplanarity:



o



Need clean e
-
d elastic sample



e
-
d Elastic rate ~ 3% of coincident rate by one positive and

one negative charge scattered into either sector.


Everything

Colpanarity

Kinematics

Full cuts

U. Kentucky, 31 March 2005



Kinematics:


p
e
=24MeV


d
=1
o

… …



Mass:
timing & tracking


Blue: everything


Red: after coplanary cut

Deuterons

Protons


+

?


e
-
d Elastic Event Selection


e
-

left, d
+

right


e
-

right, d
+

left

U. Kentucky, 31 March 2005

Preliminary T20 Result


U. Kentucky, 31 March 2005

From Measurements of the Elastic Vector
Asymmetry
A
V
ed

U. Kentucky, 31 March 2005

Deuterium Wave Functions


The NN interaction conserves only
total
angular momentum


Spin
-
1 nucleus lies in an L = 0, 2
admixture ground state:




A
tensor component

must be present to
allow

L = 2


Fourier transform into momentum space:





L = 2 component becomes dominant at
p
M

~ 0.3GeV



(Bonn Potential)

(Bonn Potential)


R
0
(
r
)
,
R
2
(
r
)

˜
R
0
(
p
)
,
˜
R
2
(
p
)


m
d
r



R
0
r


Y
110
m
d

r



R
2
r


Y
112
m
d

r




M
n
p
n
p
p
p
p
2
1
p
r
r
r














R
0
r



˜
R
0
p


,
R
2
r



˜
R
2
p


U. Kentucky, 31 March 2005

Deuteron Density Functions


Calculate the density functions:



One
-
to
-
one correspondence

between m
d

and
the (P
Z
,P
ZZ
) polarization states:







In the absence of a tensor NN component,
these plots are
spherical
and
identical


Famous “
donut
” and “
dumbbell
” shapes




m
d
r
'




m
d
r




m
d
r



m
d


1



1

1

P
Z
,
P
ZZ




1,
+1


m
d

0


0

1

P
Z
,
P
ZZ



0,
-
2




0
r
'




'
1
r



P
ZZ

P
Z

(
-
1,+1)

(+1,+1)


(0,
-
2)

U. Kentucky, 31 March 2005

Missing Mass


Only the e
-

and p
+

are measured


actually measure d(e,e’p)X and thus need cuts to ensure that X = n


Define “missing”
energy
,
momentum
, and
mass
:




Demanding that m
M

= m
n

helps ensure that X = n


Momentum magnitude corrections
greatly improve

m
M

spectra



E
M

m
d



E
p
,
p
M

q

p
p
,
m
M

E
M
2

p
M
2
U. Kentucky, 31 March 2005

Missing Momentum


Good MC agreement up to p
M

= 0.5GeV/c

Left Sector Electron

Right Sector Electron

U. Kentucky, 31 March 2005

Beam
-
Vector Asymmetry

U. Kentucky, 31 March 2005

Beam
-
Vector Asymmetry (cont.)

U. Kentucky, 31 March 2005

Tensor Asymmetry Results

U. Kentucky, 31 March 2005

Tensor Asymmetry (cont.)

U. Kentucky, 31 March 2005

Potential Dependence


Monte Carlo for
Bonn
,
Paris
, and
V18
potentials compared to
BLAST data


Potential dependence
small
compared to MEC and IC

contributions


U. Kentucky, 31 March 2005

Determination of
hP
z

U. Kentucky, 31 March 2005

D(e,e’n)
Kinematic Distribution

U. Kentucky, 31 March 2005

Missing Mass from
D(e,e’n) QES

U. Kentucky, 31 March 2005

G
E
/G
M

for the Neutron from
D(e,e’n) QES

U. Kentucky, 31 March 2005

G
n
M

U. Kentucky, 31 March 2005

G
n
E

from
D(e,e’n)

U. Kentucky, 31 March 2005

Conclusions and Outlook


World
-
class data

for

G
p
E
/G
p
M

, G
n
E
/G
n
M

, D(e,e’)
elastic

T
20

, D(e,e’p) QES A
V
ed

and

A
T
d,
,
Inclusive

H(e,e’)X
and

D(e,e’)X


Analysis still
in progress


Many other channels

to be analyzed:
H(e,e’p)

0

,
H(e,e’n)



, H(
g
,n)



, D(
g
,pn) , … etc.


Continuing to take data on

D

until June (?); expect to at
least double data set (or more!)


Shut down and decommission
; relocate detectors and
remap BLAST field

U. Kentucky, 31 March 2005

The
BLAST
ers