Robert Michaels Jefferson Lab On Behalf of the HAPPEX Collaboration Acknowledgement Talk prepared by Kai Pan MIT graduate student ID: 626543
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Slide1
PVDIS at JLab 6 GeV
Robert Michaels
Jefferson Lab
On Behalf
of
the HAPPEX
Collaboration
Acknowledgement:
Talk prepared by Kai Pan (MIT graduate student)
Parity Mini-Symposium, APS
Meeting
Apr 30 – May 3
,
2011
Slide2
Testing Electroweak Standard Model Standard Model is a successful theory. Data confirms the electroweak sector of the SM at a few 0.1%.
Deficiencies
of the Standard Model: mass origin, neutrino oscillation, matter antimatter asymmetry, hierarchy problem. People believe SM is only a piece of some larger framework, and try to find new physics beyond Standard Model.Direct Search: LHC, Tevatron, etc… (Higgs mechanism)Indirect Search: SLAC E158 (Moller), Atomic-PV, Sample, NuTeV, Qweak, PVDIS (Electroweak couplings or weak mixing angle)
Motivation #1Slide3
However, PVDIS 6GeV is NOT
to measure
θ
w, but the electroweak coupling constant combination.PVDISRunning of sin2θw
Testing Electroweak Standard ModelSlide4
Constrain the poorly known
coupling
constant combination (2C
2u-C2d)Motivation #2 Isosinglet target
D2
e (↑L)
D2
e (↓R)
VS
spin
(polarized beam,
unpolarized
target)
A =
σ
↑ -
σ
↓
σ
↑ +
σ
↓
PDF
Measurement so far not as precise as C
1q
DIS is a unique probe accessing C
2qSlide5
Constrain the poorly known coupling constant combination (2C
2u
-C
2d) 2C2u-C2d = -0.08 (+-)
0.24
Δ
(2C
2u
-C
2d
) =
0.06Slide6
Constrain the hadronic effect
Non-
perturbative
QCD (higher-twist) effectCharge Symmetry violation (equivalence of u,d quark distribution in proton and neutron)
Provide important guide on the future
PVDIS 12
GeV
upgrade, for which the ultimate goal is to extract electroweak coupling constant as well as sin
2
(
θ
w
) from the asymmetry
free from
hadronic
effects
.
Motivation
#
3Slide7
Section II: Jlab Hall A and PVDIS Experiment Setup
JLab
: Linear
accelerator provides continuous polarized electron beamEbeam = 6 GeVPbeam = 90%3 experimental halls (Hall A)Spokespersons: Xiaochao
Zheng
(
UVa
)
Bob Michaels (
JLab
)
Paul Reimer (Argonne)
Thesis
students:
Diancheng
Wang (
UVa
)
Xiaoyan
Deng (
UVa) Kai Pan (MIT)
Postdocs:
Zhiwen Zhao (
UVa) Ramesh
Subedi (UVa
, George Washington University)
A
B
CSlide8
H
igh
R
esolution Spectrometer (HRS)Beam Energy 6.067 GeV20 cm long liquid deuterium (LD
2
) target
100
uA
polarized beam with 90% beam polarization
Two kinematics
Q
2
=1.1(
GeV
)
2
; 12.9
0
; P
0
= 3.66
GeV
Q
2=1.9(GeV
)2 ; 20.00 ; P
0 = 2.63 GeV
X = 0.25 ~ 0.3
Top View
Side View
Jlab Hall A
Magnet Q, D
Magnet
Detector Hut
D1
Q1
Q2
Q3
Detector
Package
Run time: Oct – Dec 2009Slide9
Two DAQ Systems were used:
regular High Resolution Spectrometer (HRS) DAQ
Limitation: Max event taking rate is only 2KHz for each arm, which is far below the rate requirement in PVDIS.
Parity fast counting DAQ
Scaler
based (
fast
counting with very low
deadtime
)
Measured
scaler
counting rate is up to 500KHz for each arm
Hardware-based
Particle Identification (PID
)
Scalers
integrated over
helicity
periods, like an integration experiment.
PVDIS Experiment Setup
Useful for
simultaneous recording of
kinematics, efficiencies and
Particle Identification (PID)
analysis
NEWSlide10
Parity fast-counting scaler
DAQ (Hardware-based PID)
Preshower
Shower
a1
a2
a3
Ps
> a1
Ps +
Sh
> a2
GC
> a3
Discriminator
Scaler
Data
ANDingSlide11
Data Analysis Flow Chart
H
all
A Monte Carlo (HAMC)Hall A Trigger S
imulation (
HATS)
Section III: Data
Analysis Status
A
sim
Parity Data:
Pedestal subtraction
Beam linearity calibration
Selection of clean cut
Charge asymmetry analysis
Regression and dithering
A
exp
?
HRS
Parity
Track reconstruction
Beam polarization
Deadtime correction
Pion contaminaiton
Electron detection efficiency
Other correction
InputSlide12
1. Tracking reconstruction
DIS
asymmetry
is sensitive to Q^2, thus tracking reconstruction After calibration, asymmetry uncertainty due to Q^2 reconstruction is <1%Slide13
2. Beam Polarization A’ =
A
measure
/ Polarization Use Compton Polarimeter to measure the beam polarization up to 2% accuracy Moller Polarimeter
as a cross check (consistent)
P ~ 90% (+ -) 2%Slide14
3. Particle Identification Performance
Horizontal Acceptance
[m]
Electron detection efficiency
~97%
Pion
Rejection Factor
Horizontal Acceptance
[m]
Electron efficiency
97% 96% 95%
Pion
Rejection Factor
52 200 10e4
Lead glass Gas
Cherenkov
Overall
Lead Glass
Lead Glass
Asymmetry
correction due
to
electron efficiency <0.5%
pion
contamination <
0.1
%Slide15
Target
4. Simulation
Simulating experiment starting from initial beam to detector package (not included)
Incoming and scattered electron energy loss (ionization and
bremsstrahlung
)
DIS cross section and asymmetries are calculated by using world data fit (PDF)
Standard
Quadrupole
and Dipole magnet transportation functions
H
all
A M
onte
C
arlo (
HAMC
)Slide16
Target
4. Simulation
Simulating experiment starting from initial beam to detector package (not included)
Incoming and scattered electron energy loss (ionization and
bremsstrahlung
)
DIS cross section and asymmetries are calculated by using world data fit (PDF)
Standard
Quadrupole
and Dipole magnet transportation functions
H
all
A M
onte
C
arlo (
HAMC
)
Black: data
Red: simulation
ConsistentSlide17
4. SimulationSlide18
Target
4. Simulation
Simulating detector and DAQ response to the incoming physics events generated by HAMC
Deadtime
Simulation
A’ =
A
measure
(1-Deadtime)
Deadtime
data
is well understood. (consistent with the simulation)
1% (+ -)
0.2
% correction
on Asymmetry
H
all
A
T
rigger
Simulation (
HATS)
Credit:
Diancheng Wang
(Univ. Virginia graduate student)Slide19
5. Parity DAQ data analysis (Blinded raw asymmetry)
Arbitrary
shift (
blinding factor) on measured asymmetry to avoid analysis bias To do list before unblinding: Pedestal subtraction, BCM calibration, charge asymmetry analysis, selection of clean cut, regression and dithering correction, etc
B L I N D E D!
will provide a ~3% relative uncertainty compared to the simulation
90
ppm
will provide a ~4% relative uncertainty compared to the simulation
161
ppm
Online Asymmetries,
Q
2
=1.1 (
GeV
/C)
2
Q
2
=1.9 (
GeV
/C)
2
B L I N D E D!Slide20
Section IV: Summary and Outlook
Experiment will provide world highest-accuracy measurement on
(2C2u-C2d), improving the uncertainty by a factor of fourConstrain the hadronic effect, providing guidance for PVDIS 12 GeV upgrade Regular
HRS DAQ data analysis
is close
to being
finalized
Parity DAQ data analysis is
ongoing
Expected to
release
preliminary (
unblined
) asymmetry
by the end of this
summer (in time for PAVI-11 conference).
Physics Goal
Data Analysis Progress
Special thanks to :
Kai Pan,
Diancheng
Wang,
Xiaoyan
Deng (grad students)
Xiaochao
Zheng & Paul Reimer (co-spokespersons)