Transcript RHIC Spin Project Issues - UW-Madison Department of Physics

Parity Violation Experiments at SIN
(as viewed by a graduate student)
R. Balzer1, W. Haeberli2, R. Henneck1, S. Jaccard3, S.
Kistryn1,
Ch. Jacquemart1,*, J. Lang1, J. Liechti1, Th. Maier1,*, R.
Müller1,
F. Nessi-Tedaldi1,*, W. Reichart4, T. Roser1,*, M. Simonius1,
J. Smyrski1, J. Sromicki1,2, Ch. Weddigen5
1ETHZ, 2Wisconsin, 3SIN, 4Zürich, 5Karlsruhe
*Graduate
student
Thomas Roser
Haeberli Fest
June 10, 2005
Parity violation in nucleon-nucleon interaction
Electro-weak part of nucleon-nucleon
interaction
In one-boson exchange model:
N’
Weak meson-nucleon coupling
constants determined by standard
model
N’
p,r,w
P.V.
Calculable due to short range of
W,Z interaction
N
Desplanques, Donoghue and
Holstein give “best value” and
“range” for p,r,w coupling
constants:
fp , hr0 , hw0 , hr1 , hw1 , hr2
N
Parity Violating
Nucleon-Nucleon Potential
Parity violation in nuclear scattering at ~ 45 MeV
   
Az 
 
• Nuclear scattering of simple systems with less nuclear structure uncertainty
• Elastic pp scattering: Az = (  1.50  0.22 )  10-7

Az 
.074hr0  .065hw0  .074hr1  .065hw1  .030hr2
• Elastic pa scattering: Az = (  3.34  0.93 )  10-7

Az  .34 fp  .140hr0  .059hw0  .047hr1  .059hw1
• pd scattering (including part of break-up): Az = ( + 0.4  0.7 )  10-7
Parity violation in low energy scattering experiment
• To reach precision of better than 10-7:




Need about 1016 events, which is too many for counting individual
events  integrating detectors
At low energy detection of scattered particles is preferred over
transmission because the required thick target affects the beam too much
100 atm circulating gas target to maximize luminosity and minimize
thermal effects.
Scattering angle and energy cuts using target vessel walls. For pa this
allowed to select only elastic scattering.
Experimental layout
POLARIZATION
AND INTENSITY
PROFILES
Facilities at SIN, now PSI
Location of first
phase of experiment
“Haeberli Hall”
Location of second
phase of experiment
Systematic errors
• Systematic error has to be less than a few 10-8
• Good training ground for future spin physicists (needs patience and care and
enthusiasm for flipping the spin!)
• Basic approach:
 Modulate every possible parameter artificially and measure resulting
effect on Az  sensitivities
 Measure actual helicity correlated parameter modulation during
experiment
 Calculate correction/error from sensitivity and measured modulation
• Systematic error sources:
 Intensity modulations
 Position modulations
 Beam width modulations
th st nd moment)
 Transverse polarization (0 ,1 ,2
 Energy modulations
“Haeberli plot”: Comparison with PV g decays
Az ( pa )  .34 fp  .14(hr0  .6hw0 )
Low energy pp elastic scattering
Energy dependence of p.v. partial wave amplitudes 1S0 – 3P0
and 3P2 – 1D2 are given by strong phases
 only two p.v. observables
BONN
SIN
TRIUMF
hrpp  hr0  hr1  hr2
hwpp  hw0  hw1
6
Energy dependence of parity violation in pp total cross section
TRIUMF
RHIC
 ANL measurement of p-H2O indicates fast rise of Az
 Measurement of Az in pp total cross section using stored
polarized beam and internal target measuring helicity-dependent
beam lifetime (S. Vigdor)
 Possible experiment up to 250 GeV with polarized beam at
RHIC