Tue·Nov 25, 2014Tuesday·November 25, 2014

1. 01*

   Superallowed 0+ --> 0+ nuclear beta decays: 2014 critical survey, with precise results for Vud and CKM unitarity

   J.C. Hardy🇺🇸 · I.S. Towner🇺🇸

   A new critical survey is presented of all half-life, decay-energy and branching-ratio measurements related to 20 superallowed 0+ --> 0+ beta decays. Included are 222 individual measurements of comparable precision obtained from 177 published references. Compared with our last review in 2008, we have added results from 24 new publications and eliminated 9 references, the results from which having been superseded by much more precise modern data. We obtain world-average ft-values for each of the eighteen transitions that have a complete set of data, then apply radiative and isospin-symmetry-breaking corrections to extract corrected Ft values. Fourteen of these Ft values now have a precision of order 0.1% or better. In the process of obtaining these results we carefully evaluate the available calculations of the isospin-symmetry-breaking corrections by testing the extent to which they lead to Ft values consistent with conservation of the vector current (CVC). Only one set of calculations satisfactorily meets this condition. The resultant average Ft value, when combined with the muon liftime, yields the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, Vud = 0.97417 +/- 0.00021. The unitarity test on the top row of the matrix becomes |Vud|^2 + |Vus|^2 + |Vub|^2 = 0.99978 +/- 0.00055 if the Particle Data Group recommended value for Vus is used. However, recent lattice QCD calculations, not included yet in the PDG evaluation, have introduced some inconsistency into kaon-decay measurements of Vus and Vus/Vud. We examine the impact of these new results on the unitarity test and conclude that there is no evidence of any statistically significant violation of unitarity. Finally, from the Ft-value data we also set limits on the possible existence of scalar interactions.

   nucl-exhep-phnucl-thPRC(2015)·343 citations
2. 02*

   Recognizing Critical Behavior amidst Minijets at the Large Hadron Collider

   Rudolph C. Hwa🇺🇸

   The transition from quarks to hadrons in a heavy-ion collision at high energy is usually studied in two different contexts that involve very different transverse scales: local and non-local. Models that are concerned with the $p_T$ spectra and azimuthal anisotropy belong to the former, i.e., hadronization at a local point in $(\eta ,\varphi )$ space, such as the recombination model. The non-local problem has to do with quark-hadron phase transition where collective behavior through near-neighbor interaction can generate patterns of varying sizes in the $(\eta ,\varphi )$ space. The two types of problems are put together in this paper both as brief reviews separately and to discuss how they are related to each other. In particular, we ask how minijets produced at LHC can affect the investigation of multiplicity fluctuations as signals of critical behavior. It is suggested that the existing data from LHC have sufficient multiplicities in small $p_T$ intervals to make feasible the observation of distinctive features of clustering of soft particles, as well as voids, that characterize the critical behavior at phase transition from quarks to hadrons, without any ambiguity posed by the clustering of jet particles.

   nucl-exhep-phnucl-thAdv.High Energy Phys.(2015)·11 citations
3. 03*

   BBN And The CMB Constrain Neutrino Coupled Light WIMPs

   Kenneth M. Nollett🇺🇸 · Gary Steigman🇺🇸

   (abridged) In the presence of a light WIMP (mass m_chi < 30 MeV), there are degeneracies among the WIMP's nature, its couplings to standard model particles, its mass, and the number of equivalent (additional) neutrinos, Delta N_nu. These degeneracies cannot be broken by the CMB constraint on the effective number of neutrinos, N_eff. However, since big bang nucleosynthesis (BBN) is also affected by a light WIMP and equivalent neutrinos, complementary BBN and CMB constraints can break some of the degeneracy. In a previous paper BBN and CMB were combined to explore allowed ranges for m_chi, Delta N_nu, and N_eff for light WIMPs that annihilate electromagnetically (EM) to photons and/or electrons/positrons. In this paper BBN predictions with a light WIMP that only couples to neutrinos are calculated. Recent observed abundances of ^2H and ^4He are used to limit m_chi, Delta N_nu, N_eff, and the present-day baryon density. Allowing for a neutrino coupled light WIMP and nonzero Delta N_nu, combined BBN and CMB data give lower limits to m_chi, with a best fit m_chi > 35 MeV, equivalent to no light WIMP at all. All masses below 4--9 MeV (depending on spin) are excluded. Without any light WIMP, BBN alone prefers Delta N_nu = 0.50 +- 0.23, favoring neither Delta N_nu = 0, nor a fully thermalized sterile neutrino (Delta N_nu = 1). This result is consistent with the CMB constraint, N_eff = 3.30 +- 0.27, limiting "new physics" between BBN and recombination. Combining BBN and CMB data gives Delta N_nu = 0.35 +- 0.16 and N_eff = 3.40 +- 0.16; while BBN and the CMB combined require Delta N_nu > 0 at ~98% confidence, they disfavor Delta N_nu > 1 at > 99% confidence. Allowing a neutrino-coupled light WIMP extends the allowed range slightly downward for Delta N_nu and slightly upward for N_eff simultaneously, leaving best-fit values unchanged.

   ↳ astro-ph.COnucl-exnucl-thPRD(2015)·183 citations
4. 04*

   Luminescence and scintillation properties of CsI -- a potential cryogenic scintillator

   V. B. Mikhailik · V. Kapustyanyk · V. Tsybulskyi · V. Rudyk · H. Kraus🇬🇧

   Caesium iodide is one of the more extensively studied scintillators. Here we present X-ray luminescence spectra, scintillation light output and decay curves as function of temperature, from room temperature down to below 10 K. Features of the observed intrinsic luminescence are explained in terms of radiative recombination of on- and off-centre STE. A model permitting interpretation of the dynamics of luminescence changes in CsI with temperature is suggested. This model includes adiabatic potential energy surfaces (APES) associated with singlet and triplet states of self-trapped excitons (STE) and explains the variation of the luminescence spectra with temperature as a result of re-distribution in the population between on- and off-centre STE. The temperature dependence of the scintillation light yield is discussed in the framework of the Onsager mechanism.

   ↳ cond-mat.mtrl-scinucl-exphysics.ins-detPhys.Status Solidi B(2015)·28 citations
5. 05*

   Measurement of the ${\nu }_{\mu }$ CCQE cross section on carbon with the ND280 detector at T2K

   T2K Collaboration: K. Abe🇯🇵 · J. Adam🇺🇸 · H. Aihara🇯🇵 · T. Akiri🇺🇸 · C. Andreopoulos🇬🇧 · S. Aoki🇯🇵 · A. Ariga🇨🇭 · S. Assylbekov🇺🇸 · D. Autiero🇫🇷 · M. Barbi🇨🇦 · G. J. Barker🇬🇧 · G. Barr🇬🇧 and 332 other authors

   The Charged-Current Quasi-Elastic (CCQE) interaction, ${\nu }_l+n\to l^{-}+p$, is the dominant CC process at $E_{\nu }\sim 1$ GeV and contributes to the signal in accelerator-based long-baseline neutrino oscillation experiments operating at intermediate neutrino energies. This paper reports a measurement by the T2K experiment of the ${\nu }_{\mu }$ CCQE cross section on a carbon target with the off-axis detector based on the observed distribution of muon momentum ($p_{\mu }$) and angle with respect to the incident neutrino beam (${\theta }_{\mu }$). The flux-integrated CCQE cross section was measured to be $(0.83\pm 0.12)\times 10^{-38}{\text{ cm}}^2$ in good agreement with NEUT MC value of $0.88\times 10^{-38}{\text{ cm}}^2$. The energy dependence of the CCQE cross section is also reported. The axial mass, $M_A^{QE}$, of the dipole axial form factor was extracted assuming the Smith-Moniz CCQE model with a relativistic Fermi gas nuclear model. Using the absolute (shape-only) $p_{\mu }cos{\theta }_{\mu }$ distribution, the effective $M_A^{QE}$ parameter was measured to be $1.26_{-0.18}^{+0.21}\text{ GeV}/c^2$ ($1.43_{-0.22}^{+0.28}\text{ GeV}/c^2$).

   ↳ hep-exnucl-exPRD(2015)·94 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.