arXiv subjects

J. Krempel

Publications and source records attributed to J. Krempel.

40 records · Page 3Linked to original sources

arXiv2012

Determination of the Weak Axial Vector Coupling from a Measurement of the Beta-Asymmetry Parameter A in Neutron Beta Decay

We report on a new measurement of the neutron beta-asymmetry parameter $A$ with the instrument \perkeo. Main advancements are the high neutron polarization of $P = 99.7(1)%$ from a novel arrangement of super mirror polarizers and reduced background from improvements in beam line and shielding. Leading corrections were thus reduced by a factor of 4, pushing them below the level of statistical error and resulting in a significant reduction of systematic uncertainty compared to our previous experiments. From the result $A_0 = -0.11996(58)$, we derive the ratio of the axial-vector to the vector coupling constant $λ= g_\mathrm{A}/g_\mathrm{V} = -1.2767(16)$

hep-ex↗

arXiv2011

An Improved Search for the Neutron Electric Dipole Moment

A permanent electric dipole moment of fundamental spin-1/2 particles violates both parity (P) and time re- versal (T) symmetry, and hence, also charge-parity (CP) symmetry since there is no sign of CPT-violation. The search for a neutron electric dipole moment (nEDM) probes CP violation within and beyond the Stan- dard Model. The experiment, set up at the Paul Scherrer Institute (PSI), an improved, upgraded version of the apparatus which provided the current best experimental limit, dn < 2.9E-26 ecm (90% C.L.), by the RAL/Sussex/ILL collaboration: Baker et al., Phys. Rev. Lett. 97, 131801 (2006). In the next two years we aim to improve the sensitivity of the apparatus to sigma(dn) = 2.6E-27 ecm corresponding to an upper limit of dn < 5E-27 ecm (95% C.L.), in case for a null result. In parallel the collaboration works on the design of a new apparatus to further increase the sensitivity to sigma(dn) = 2.6E-28 ecm.

nucl-ex↗

arXiv2007

Measurement of the Proton Asymmetry Parameter C in Neutron Beta Decay

The proton asymmetry parameter C in neutron decay describes the correlation between neutron spin and proton momentum. In this Letter, the first measurement of this quantity is presented. The result C=-0.2377(26) agrees with the Standard Model expectation. The coefficient C provides an additional parameter for new and improved Standard Model tests. From a differential analysis of the same data (assuming the Standard Model), we obtain lambda=-1.275(16) as ratio of axial-vector and vector coupling constant.

hep-ph↗

arXiv2007

Measurement of the Neutrino Asymmetry Parameter B in Neutron Decay

A new measurement of the neutrino asymmetry parameter B in neutron decay, the angular correlation between neutron spin and anti-neutrino momentum, is presented. The result, B=0.9802(50), agrees with the Standard Model expectation and earlier measurements, and permits improved tests on ``new physics'' in neutron decay.

hep-ph↗