towards improved polarimetry at rhic
DESCRIPTION
Towards Improved Polarimetry at RHIC. Yousef I. Makdisi Brookhaven National Laboratory For The RHIC Polarimetry Group. Outline. A brief introduction to the polarimetry components The P-Carbon CNI polarimeters Current R&D efforts Upgrade plans The Polarized Jet Target issues - PowerPoint PPT PresentationTRANSCRIPT
Current and Future Transverse Spin at PHENIX
Yousef Makdisi Spin 2008 October 6-11, 2008
Towards Improved Polarimetry at RHIC
Yousef I. MakdisiBrookhaven National LaboratoryForThe RHIC
Polarimetry Group
Outline
A brief introduction to the polarimetry components
The P-Carbon CNI polarimeters
Current R&D efforts
Upgrade plans
The Polarized Jet Target issues
Plans for the Jet for Run 9 Summary
The RHIC Polarimetry Complex
Self Calibrating
The Polarized Hydrogen Jet target
Calibrated from the Jet Data
p-Carbon Polarimeters
p-Carbon Polarimeters
(t0,x)Kinematic Fit
E
5.486 MeV (85%)5.443 MeV (12%)
p-Carbon Polarimeters Energy Correction Vipuli
Energy calibration uses alpha sources followed by a fit to TOF/
Energy relation to extract the dead layer thicknessThe average
thickness is ~ 80 gm/cm2 >> 25-30 gm/cm2 expected The energy
correction in the silicon carbon could be charge dependent
!!
R&D Effort At The Tandem Morozov
The BNL Tandem: Carbon beams to scan energies of interest with
varying intensities up to 4.106/cm2: 0.3 5 MeV (wider than the
current range to reach the Alpha energy from the Americium source)
Charge of +1, +2, and +3 This will provide a good energy
calibration Will decouple the time and energy dependences Use alpha
sources impinging forward and backward to determine the effective
silicon thickness and assess potential degradation Use a foil to
simulate the polarimeter carbon target
p-Carbon Polarimeters Looking Ahead
Test new Hammamatsu photodiode detectors and array under similar
conditionsA factor of 4 energy resolution good for going to lower t
We will also test a duel-silicon detector system with a thin 5 m
followed by the 300 m detectorsIdentify the carbon charge with the
thin detector at energies between 0.3 1 MeV. This then drives the
energy loss (dead layer) determination from the earlier dataAn
added bonus, the thin detector could provide a trigger. It is blind
to minimum ionizing prompts, so less rate dependentTest the
existing charge amplifier with a lower shaping timeTest a new low
capacitance cable between the detector and preamp
Test a current amplifier concept: better for high capacitance
detectors and high rate environment. Are the noise levels
acceptable? For high rate we will try to reduce the silicon volume
current by reducing area and thickness
Testing in situ w/ New Polarimeter Upgrade
Run 9: install the new detectors in a two arm 450 configuration in
one of the duel polarimeters:
Compare its performance to the existing systems under similar beam conditions
Assess resilience to radiation
Include a detector to get a handle on the prompts or t0
timing
Jet Target experienced higher background levels H.
Okada
Background Under The Jet Elastic Signal
Studied the contribution fromeach beam separately the incident beam
and the displaced beam
If elastics, expected a beam related Asymmetry. None was found
Two beam mode did not show increased background!
With beam incident at the jet FWHM position did not observe
lower asymmetry within stats.
Collimators were removed this Run
The Polarized Jet Target Two Beam Mode
x
y
jet
(+10, -10) mm
(0, -1.5) mm
-10
+10
(0, -7) mm
For Run 9
Re-install and survey the collimators albeit with a wider vertical
opening for better two-beam acceptance. Re-establish conditions
similar to Run6 The two beam mode allows for simultaneous
calibration of both the Blue and Yellow p-Carbon polarimeters
instead of alternating between them. Use one beam only impinging on
the jet center and assess the associated background Use one beam
displaced by 10 x 10 mm in x and y respectively and determine the
background under the signal if any Use a two beam mode to see if
the background is any different Run with the beam at the FWHM
position for enough statistics to see if there is any jet beam
polarization profile Repeat jet beam depolarization measurements
with the two beam mode
Run 9 +
We need to revisit the molecular hydrogen background.This still
represents the largest systematic error on the jet measurement
Re-do the electron beam measurement with a time of flight measurement instead of the magnetic measurement of the outgoing products.(A. Belov, INR)
A good statistical measurement and calibration at RHIC injection
energy to couple the AGS and RHIC measurements and assure that we
do not lose polarization on the RHIC ramp
Summary
We continue to strive for consistent polarimetry measurements from
one run to the next We are embarking on a significant R&D
effort for better detector performance especially in anticipating
higher rate environment
Continued efforts to understand the associated backgrounds and reduce the associated systematic errors
It is gratifying to see the analyses of both the polarimaters
and jet data completed in half the earlier times. A testimonial to
the analysis maturity and thanks to the diligence of Hiromi Okada
(BNL Spin Phys. Group, now at KEK-Jparc) Vipuli Dharmawardane (New
Mexico State University)