Fri·Aug 8, 2014Friday·August 8, 2014

1. 01*

   Measurements of Double-Polarized Compton Scattering Asymmetries and Extraction of the Proton Spin Polarizabilities

   P. P. Martel🇩🇪 · R. Miskimen🇺🇸 · P. Aguar-Bartolome🇩🇪 · J. Ahrens🇩🇪 · C. S. Akondi🇺🇸 · J. R. M. Annand🇬🇧 · H. J. Arends🇩🇪 · W. Barnes🇺🇸 · R. Beck🇩🇪 · A. Bernstein🇺🇸 · N. Borisov🇷🇺 · A. Braghieri🇮🇹 and 67 other authors

   The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to measure the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the $\Delta (1232)$ region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields ${\gamma }_{E1E1}=-3.5\pm 1.2$, ${\gamma }_{M1M1}=3.16\pm 0.85$, ${\gamma }_{E1M2}=-0.7\pm 1.2$, and ${\gamma }_{M1E2}=1.99\pm 0.29$, in units of $10^{-4}$ fm${}^4$.

   nucl-exPRL(2015)·58 citations
2. 02*

   Medium-induced optical effects for prompt photons

   Akihiko Monnai🇺🇸

   Electromagnetic aspects of a QCD matter have been a hot topic in recent years. High-energy heavy-ion experiments revealed that flow harmonics of direct photons are not explained by most hydrodynamic models. In this work I discuss possible effects of refraction by the hot medium since it can work as a lens which converts its geometrical anisotropy into momentum anisotropy of photons. Then elliptic flow and higher-order harmonics of prompt photons are estimated numerically. The results indicate that they could be small but have phenomenologically non-trivial consequences.

   ↳ nucl-thhep-phnucl-exNPA(2020)·9 citations
3. 03*

   Measurement of the Michel Parameter xi" in Polarized Muon Decay and Implications on Exotic Couplings of the Leptonic Weak Interaction

   R. Prieels🇧🇪 · O. Naviliat-Cuncic🇫🇷 · P. Knowles🇧🇪 · P. Van Hove🇧🇪 · X. Morelle🇨🇭 · J. Egger🇨🇭 · J. Deutsch🇧🇪 · J. Govaerts🇧🇪 · W. Fetscher🇨🇭 · K. Kirch🇨🇭 · J. Lang🇨🇭

   The Michel parameter xi" has been determined from a measurement of the longitudinal polarization of positrons emitted in the decay of polarized and depolarized muons. The result, xi" = 0.981 +- 0.045stat +- 0.003syst, is consistent with the Standard Model prediction of unity, and provides an order of magnitude improvement in the relative precision of this parameter. This value sets new constraints on exotic couplings beyond the dominant V-A description of the leptonic weak interaction.

   ↳ hep-exhep-phnucl-exPRD(2014)·11 citations
4. 04*

   Progress towards precision measurements of beta-decay correlation parameters using atom and ion traps

   D. Melconian🇺🇸 · R.S. Behling🇺🇸 · B. Fenker🇺🇸 · M. Mehlman🇺🇸 · P.D. Shidling🇺🇸 · M. Anholm · D. Ashery · J.A. Behr🇨🇦 · A. Gorelov · G. Gwinner🇨🇦 · K. Olchankski · S. Smale

   The correlations of the decay products following the beta decay of nuclei have a long history of providing a low-energy probe of the fundamental symmetries of our universe. Over half a century ago, the correlation of the electrons following the decay of polarized 60Co demonstrated that parity is not conserved in weak interactions. Today, the same basic idea continues to be applied to search for physics beyond the standard model: make precision measurements of correlation parameters and look for deviations compared to their standard model predictions. Efforts to measure these parameters to the 0.1% level utilizing atom and ion trapping techniques are described.

   ↳ physics.ins-detnucl-exPoS(2014)·2 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.