Wed·Dec 5, 2018Wednesday·December 5, 2018

1. 01*

   Charged-particle pseudorapidity density at mid-rapidity in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV

   ALICE Collaboration

   The pseudorapidity density of charged particles, \rm{d}\it{N}_\rm{ch}/\rm{d}\it{\eta}, in p-Pb collisions has been measured at a centre-of-mass energy per nucleon-nucleon pair of $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV at mid-pseudorapidity for non-single-diffractive events. The results cover 3.6 units of pseudorapidity, $|\eta |<1.8$. The \rm{d}\it{N}_\rm{ch}/\rm{d}\it{\eta} value is $19.1\pm 0.7$ at $|\eta |<0.5$. This quantity divided by \langle N_\rm{part} \rangle/2, is $4.73\pm 0.20$, which is 9.5% higher than the corresponding value for p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. Measurements are compared with models based on different mechanisms for particle production. All models agree within uncertainties with data in the Pb-going side, while HIJING overestimates, showing a symmetric behaviour, and EPOS underestimates the p-going side of the \rm{d}\it{N}_\rm{ch}/\rm{d}\it{\eta} distribution. Saturation-based models reproduce the distributions well for $\eta >-1.3$. The \rm{d}\it{N}_\rm{ch}/\rm{d}\it{\eta} is also measured for different centrality estimators, based both on the charged-particle multiplicity and on the energy deposited in the Zero-Degree Calorimeters. A study of the implications of the large multiplicity fluctuations due to the small number of participants for systems like p-Pb in the centrality calculation for multiplicity-based estimators is discussed, demonstrating the advantages of determining the centrality with energy deposited near beam rapidity.

   nucl-exhep-exEPJC(2019)·45 citations
2. 02*

   Towards the P-wave nucleon-pion scattering amplitude in the $\Delta (1232)$ channel

   Srijit Paul🇨🇾 · Giorgio Silvi🇩🇪 · Constantia Alexandrou🇨🇾 · Giannis Koutsou🇨🇾 · Stefan Krieg🇩🇪 · Luka Leskovec🇺🇸 · Stefan Meinel🇺🇸 · John Negele🇺🇸 · Marcus Petschlies🇩🇪 · Andrew Pochinsky🇺🇸 · Gumaro Rendon🇺🇸 · Sergey Syritsyn🇺🇸

   We use lattice QCD and the Lüscher method to study elastic pion-nucleon scattering in the isospin $I=3/2$ channel, which couples to the $\Delta (1232)$ resonance. Our $N_f=2+1$ flavor lattice setup features a pion mass of $m_{\pi }\approx 250$ MeV, such that the strong decay channel $\Delta \to \pi N$ is close to the threshold. We present our method for constructing the required lattice correlation functions from single- and two-hadron interpolating fields and their projection to irreducible representations of the relevant symmetry group of the lattice. We show preliminary results for the energy spectra in selected moving frames and irreducible representations, and extract the scattering phase shifts. Using a Breit-Wigner fit, we also determine the resonance mass $m_{\Delta }$ and the $g_{\Delta -\pi N}$ coupling.

   ↳ hep-latnucl-exnucl-thPoS(2018)·12 citations
3. 03*

   Constraints on Neutrino Lifetime from the Sudbury Neutrino Observatory

   SNO Collaboration: B. Aharmim🇨🇦 · S. N. Ahmed🇨🇦 · A. E. Anthony🇺🇸 · N. Barros🇵🇹 · E. W. Beier🇺🇸 · A. Bellerive🇨🇦 · B. Beltran🇨🇦 · M. Bergevin🇺🇸 · S. D. Biller🇬🇧 · R. Bonventre🇺🇸 · K. Boudjemline🇨🇦 · M. G. Boulay🇨🇦 and 118 other authors

   The long baseline between the Earth and the Sun makes solar neutrinos an excellent test beam for exploring possible neutrino decay. The signature of such decay would be an energy-dependent distortion of the traditional survival probability which can be fit for using well-developed and high precision analysis methods. Here a model including neutrino decay is fit to all three phases of ${}^8$B solar neutrino data taken by the Sudbury Neutrino Observatory. This fit constrains the lifetime of neutrino mass state ${\nu }_2$ to be $>8.08\times 10^{-5}$ s/eV at $90\%$ confidence. An analysis combining this SNO result with those from other solar neutrino experiments results in a combined limit for the lifetime of mass state ${\nu }_2$ of $>1.04\times 10^{-3}$ s/eV at $99\%$ confidence.

   ↳ hep-exnucl-exPRD(2019)·53 citations
4. 04*

   Search for Tri-Nucleon Decay in the Majorana Demonstrator

   S.I. Alvis🇺🇸 · I.J. Arnquist🇺🇸 · F.T. Avignone III🇺🇸 · A.S. Barabash🇷🇺 · C.J. Barton🇺🇸 · F.E. Bertrand🇺🇸 · B. Bos🇺🇸 · V. Brudanin🇷🇺 · M. Busch🇺🇸 · M. Buuck🇺🇸 · T.S. Caldwell🇺🇸 · Y-D. Chan🇺🇸 and 54 other authors

   The Majorana Demonstrator is an ultra low-background experiment searching for neutrinoless double-beta decay in ${}^{76}$Ge. The heavily shielded array of germanium detectors, placed nearly a mile underground at the Sanford Underground Research Facility in Lead, South Dakota, also allows searches for new exotic physics. We present the first limits for tri-nucleon decay-specific modes and invisible decay modes for Ge isotopes. We find a half-life limit of $4.9\times 10^{25}$ yr for the decay ${}^{76}\mathrm{Ge}(\mathrm{ppn})\to {}^{73}\mathrm{Zn}{e}^{+}{\pi }^{+}$ and $4.7\times 10^{25}$ yr for the decay ${}^{76}\mathrm{Ge}(\mathrm{ppp}){\to }^{73}\mathrm{Cu}{e}^{+}{\pi }^{+}{\pi }^{+}$. The half-life limit for the invisible tri-proton decay mode of ${}^{76}$Ge was found to be $7.5\times 10^{24}$ yr.

   ↳ hep-exnucl-exphysics.ins-detPRD(2019)·29 citations
5. 05*

   A magic magnetic field to measure the neutron electric dipole moment

   G. Pignol🇫🇷

   New sources of CP violation beyond the Standard Model of particle physics could be revealed in the laboratory by measuring a non-zero electric dipole moment (EDM) of a spin 1/2 particle such as the neutron. Despite the great sensitivity attained after 60 years of developments, the result of the experiments is still compatible with zero. Still, new experiments have a high discovery potential since they probe new physics at the multi-TeV scale, beyond the reach of direct searches at colliders. Progress in precision on the neutron EDM is limited by a systematic effect arising from the relativistic motional field $\vec{E}\times \vec{v}/c^2$ experienced by the particles moving in the measurement chamber in combination with the residual magnetic gradients. This effect would normally forbid a significant increase of the size of the chamber, sadly hindering the increase of neutron statistics. We propose a new measurement concept to evade this limitation in a room-temperature experiment employing a mercury co-magnetometer. It consists ajusting the static magnetic field $B_0$ to a `magic' value which cancels the false EDM of the mercury. The magic setting is $7.2\text{muT}$ for a big cylindrical double-chamber of diameter $100$~cm.

   ↳ physics.ins-dethep-exnucl-exPLB(2019)·11 citations
6. 06*

   Dipole-dipole interactions between neutrons

   Renato Higa🇧🇷 · James F. Babb🇺🇸 · Mahir S. Hussein🇧🇷

   In this work we present results of the dipole-dipole interactions between two neutrons, a neutron and a conducting wall, and a neutron between two walls. As input, we use dynamical electromagnetic dipole polarizabilities fitted to chiral EFT results up to the pion production threshold and at the onset of the Delta resonance. Our work can be relevant to the physics of confined ultracold neutrons inside bottles.

   ↳ nucl-thhep-phnucl-exSpringer Proc.Phys.(2020)·1 citation

* 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.