Wed·Jun 10, 2015Wednesday·June 10, 2015

1. 01*

   Two photon exchange amplitude with \pi N intermediate states: spin-1/2 and spin-3/2 channels

   Dmitry Borisyuk🇺🇦 · Alexander Kobushkin🇺🇦

   We calculate two-photon exchange (TPE) amplitudes for the elastic electron-proton scattering, and take into account intermediate hadronic states containing \pi N system with total angular momentum 1/2 or 3/2, which includes 8 different channels. This is the improvement of our previous calculation, where only the \pi N states with quantum numbers of \Delta(1232) resonance were included. The results show good consistency with recent experimental data. At high Q^2, newly-calculated contributions affect the correction to the measured proton form factor ratio \mu G_E/G_M. The total correction becomes somewhat smaller compared to our previous work, but is still significant and grows approximately linearly with Q^2. Comparing contributions of different channels, we found that larger contributions come from the channels with quantum numbers of lightest resonances.

   ↳ hep-phnucl-exnucl-thPRC(2015)·32 citations
2. 02*

   Fabrication of silica aerogel with $n$ = 1.08 for $e^{+}/{\mu }^{+}$ separation in a threshold Cherenkov counter of the J-PARC TREK/E36 experiment

   Makoto Tabata🇯🇵 · Akihisa Toyoda🇯🇵 · Hideyuki Kawai🇯🇵 · Youichi Igarashi🇯🇵 · Jun Imazato🇯🇵 · Suguru Shimizu🇯🇵 · Hirohito Yamazaki🇯🇵

   This study presents the development of hydrophobic silica aerogel for use as a radiator in threshold-type Cherenkov counters. These counters are to be used for separating positrons and positive muons produced by kaon decay in the J-PARC TREK/E36 experiment. We chose to employ aerogel with a refractive index of 1.08 to identify charged particles with momenta of approximately 240 MeV/$c$, and the radiator block shape was designed with a trapezoidal cross-section to fit the barrel region surrounding the kaon stopping target in the center of the TREK/E36 detector system. Including spares, we obtained 30 crack-free aerogel blocks segmented into two layers, each layer having a thickness of 2 cm and a length of 18 cm, to fill 12 counter modules. Optical measurements showed that the produced aerogel tiles had the required refractive indices and transparency.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2015)·14 citations
3. 03*

   The torque effect and fluctuations of entropy deposition in rapidity in ultra-relativistic nuclear collisions

   Piotr Bozek🇵🇱 · Wojciech Broniowski🇵🇱

   The decorrelation of the orientation of the event-plane angles in the initial state of relativistic Pb-Pb and p-Pb collisions, the "torque effect," is studied in a model of entropy deposition in the longitudinal direction involving fluctuations of the longitudinal source profile on large scales. The radiation from a single wounded nucleon is asymmetric in space-time rapidity. It is assumed that the extent in rapidity of the region of deposited entropy is random. Fluctuations in the deposition of entropy from each source increase the event-plane decorrelation: for Pb-Pb collisions they improve the description of the data, while for p-Pb collisions the mechanism is absolutely essential to generate any sizable decorrelation. We also show that the experimental data for rank-four flow may be explained via folding of the elliptic flow. The results suggest the existence of long range fluctuations in the space-time distribution of entropy in the initial stages of relativistic nuclear collisions.

   ↳ nucl-thhep-phnucl-exPLB(2016)·75 citations
4. 04*

   Generalized perturbations in neutrino mixing

   Jiajun Liao🇺🇸 · D. Marfatia🇺🇸 · K. Whisnant🇺🇸

   We derive expressions for the neutrino mixing parameters that result from complex perturbations on (1) the Majorana neutrino mass matrix (in the basis of charged lepton mass eigenstates) and on (2) the charged lepton mass matrix, for arbitrary initial (unperturbed) mixing matrices. In the first case, we find that the phases of the elements of the perturbation matrix, and the initial values of the Dirac and Majorana phases, strongly impact the leading order corrections to the neutrino mixing parameters and phases. For experimentally compatible scenarios wherein the initial neutrino mass matrix has $\mu -\tau$ symmetry, we find that the Dirac phase can take any value under small perturbations. Similarly, in the second case, perturbations to the charged lepton mass matrix can generate large corrections to the mixing angles and phases of the PMNS matrix. As an illustration of our generalized procedure, we apply it to a situation in which nonstandard scalar and nonstandard vector interactions simultaneously affect neutrino oscillations.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2015)·12 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.