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A portable cryostat for the cold transfer of polarized solid HD targets: HDice-I

Description: A device has been developed with moveable liquid nitrogen and liquid helium volumes that is capable of reaching over two meters into the coldest regions of a cryostat or dilution refrigerator and reliably extracting or installing a target of solid, polarized hydrogen deuteride (HD). This Transfer Cryostat incorporates a cylindrical neodymium rare-earth magnet that is configured as a Halbach dipole, which is maintained at 77 K and produces a 0.1 T field around the HD target. Multiple layers provide a hermetic 77 K-shield as the device is used to maintain a target at 2 K during a transfer between cryostats. Tests with frozen-spin HD show negligible polarization loss for either H or D over typical transfer periods. Multiple target transfers with this apparatus have shown an overall reliability of about 95% per transfer, which is a significant improvement over earlier versions of the device.
Date: February 1, 2014
Creator: Bass, Christopher D.; Sandorfi, Andy M.; Bade, C.; Blecher, M.; Caracappa, A.; D'Angelo, A. et al.
Partner: UNT Libraries Government Documents Department

Precision measurement of the weak mixing angle in Moller scattering

Description: We report on a precision measurement of the parity-violating asymmetry in fixed target electron-electron (Moeller) scattering: A{sub PV} = (-131 {+-} 14 (stat.) {+-} 10 (syst.)) x 10{sup -9}, leading to the determination of the weak mixing angle sin{sup 2} {theta}{sub W}{sup eff} = 0.2397 {+-} 0.0010 (stat.) {+-} 0.0008 (syst.), evaluated at Q{sup 2} = 0.026 GeV{sup 2}. Combining this result with the measurements of sin{sup 2} {theta}{sub W}{sup eff} at the Z{sup 0} pole, the running of the weak mixing angle is observed with over 6{sigma} significance. The measurement sets constraints on new physics effects at the TeV scale.
Date: May 4, 2005
Creator: Anthony, P.L.; Arnold, R.G.; Arroyo, C.; Bega, K.; Biesiada, J.; Bosted, P.E. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the N --> Delta^+ (1232) Transition at High-Momentum Transfer by pi^0 Electroproduction

Description: We report a new measurement of the exclusive electroproduction reaction gamma*_p --> pi0_p to explore the evolution from soft nonperturbative physics to hard processes via the Q2 dependence of the magnetic (M1+), electric (E1+), and scalar (S1+) multipoles in the N --> Delta transition. 9000 differential cross section data points cover W from threshold to 1.4 GeV/c2, 4pi center-of-mass solid angle, and Q2 from 3 to 6 GeV2/c2, the highest yet achieved. It is found that the magnetic form factor G^*M decreases with Q2 more steeply than the proton magnetic form factor, the ratio E1+/M1+ is small and negative, indicating strong helicity nonconservation, and the ratio S1+/M1+ is negative, while its magnitude increases with Q2.
Date: September 1, 2006
Creator: Ungaro, M.; Stoler, P.; Aznauryan, I.; Burkert, V. D.; Joo, K.; Smith, L. C. et al.
Partner: UNT Libraries Government Documents Department