Fri·Nov 13, 2015Friday·November 13, 2015

1. 01*

   Heavy-ion double charge exchange reactions: a tool towards 0v\b{eta}\b{eta} nuclear matrix elements

   F. Cappuzzello🇮🇹 · M. Cavallaro🇮🇹 · C. Agodi🇮🇹 · M. Bond`ı🇮🇹 · D. Carbone🇮🇹 · A. Cunsolo🇮🇹 · A. Foti🇮🇹

   The knowledge of the nuclear matrix elements for the neutrinoless double beta decay is fundamental for neutrino physics. In this paper, an innovative technique to extract information on the nuclear matrix elements by measuring the cross section of a double charge exchange nuclear reaction is proposed. The basic point is that the initial and final state wave functions in the two processes are the same and the transition operators are similar. The double charge exchange cross sections can be factorized in a nuclear structure term containing the matrix elements and a nuclear reaction factor. First pioneering experimental results for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV incident energy show that such cross section factorization reasonably holds for the crucial 0+ --> 0+ transition to 40Args, at least at very forward angles.

   nucl-exnucl-thEPJA(2015)·152 citations
2. 02*

   Bayesian parameter estimation for effective field theories

   S. Wesolowski🇺🇸 · N. Klco🇺🇸 · R.J. Furnstahl🇺🇸 · D.R. Phillips🇺🇸 · A. Thapaliya🇺🇸

   We present procedures based on Bayesian statistics for estimating, from data, the parameters of effective field theories (EFTs). The extraction of low-energy constants (LECs) is guided by theoretical expectations in a quantifiable way through the specification of Bayesian priors. A prior for natural-sized LECs reduces the possibility of overfitting, and leads to a consistent accounting of different sources of uncertainty. A set of diagnostic tools are developed that analyze the fit and ensure that the priors do not bias the EFT parameter estimation. The procedures are illustrated using representative model problems, including the extraction of LECs for the nucleon mass expansion in SU(2) chiral perturbation theory from synthetic lattice data.

   ↳ nucl-thhep-phnucl-exphysics.data-anJ.Phys.G(2016)·145 citations
3. 03*

   Probing surface distributions of $\alpha$ clusters in ${}^{20}$Ne via $\alpha$-transfer reaction

   Tokuro Fukui🇯🇵 · Yasutaka Taniguchi · Tadahiro Suhara🇯🇵 · Yoshiko Kanada-En'yo🇯🇵 · Kazuyuki Ogata🇯🇵

   Direct evidence of the $\alpha$-cluster manifestation in bound states has not been obtained yet, although a number of experimental studies were carried out to extract the information of the clustering. In particular in conventional analyses of $\alpha$-transfer reactions, there exist a few significant problems on reaction models, which are insufficient to qualitatively discuss the cluster structure. We aim to verify the development of the $\alpha$-cluster structure from observables. As the first application, we plan to extract the spatial information of the cluster structure of the ${}^{20}$Ne nucleus in its ground state through the cross section of the $\alpha$-transfer reaction ${}^{16}$O(${}^6$Li,~$d$)${}^{20}$Ne. For the analysis of the transfer reaction, we work with the coupled-channel Born approximation (CCBA) approach, in which the breakup effect of ${}^6$Li is explicitly taken into account by means of the continuum-discretized coupled-channel method based on the three-body $\alpha +d+{}^{16}$O model. The two methods are adopted to calculate the overlap function between ${}^{20}$Ne and $\alpha +{}^{16}$O; one is the microscopic cluster model (MCM) with the generator coordinate method, and the other is the phenomenological two-body potential model (PM). We show that the CCBA calculation with the MCM wave function gives a significant improvement of the theoretical result on the angular distribution of the transfer cross section, which is consistent with the experimental data. Employing the PM, it is discussed which region of the cluster wave function is probed on the transfer cross section. It is found that the surface region of the cluster wave function is sensitive to the cross section. The present work is situated as the first step in obtaining important information to systematically investigate the cluster structure.

   ↳ nucl-thnucl-exPRC(2016)·19 citations
4. 04*

   Shell model description of Gamow-Teller strengths in $pf$-shell nuclei

   Vikas Kumar · P.C. Srivastava

   A systematic shell model description of the experimental Gamow-Teller transition strength distributions in ${}^{42}$Ti, ${}^{46}$Cr, ${}^{50}$Fe and ${}^{54}$Ni is presented. These transitions have been recently measured via $\beta$ decay of these $T_z$=-1 nuclei, produced in fragmentation reactions at GSI and also with (${}^3${He},$t$) charge-exchange (CE) reactions corresponding to $T_z=+1$ to $T_z=0$ carried out at RCNP-Osaka.The calculations are performed in the $pf$ model space, using the GXPF1a and KB3G effective interactions. Qualitative agreement is obtained for the individual transitions, while the calculated summed transition strengths closely reproduce the observed ones.

   ↳ nucl-thnucl-exEPJA(2016)·22 citations
5. 05*

   Linear and cubic response to the initial eccentricity in heavy-ion collisions

   Jacquelyn Noronha-Hostler🇺🇸 · Li Yan🇫🇷 · Fernando G. Gardim🇧🇷 · Jean-Yves Ollitrault🇫🇷

   We study the relation between elliptic flow, $v_2$ and the initial eccentricity, ${\epsilon }_2$, in heavy-ion collisions, using hydrodynamic simulations. Significant deviations from linear eccentricity scaling are seen in more peripheral collisions. We identify the mechanism responsible for these deviations as a cubic response, which we argue is a generic property of the hydrodynamic response to the initial density profile. The cubic response increases elliptic flow fluctuations, thereby improving agreement of initial condition models with experimental data.

   ↳ nucl-thhep-phnucl-exPRC(2016)·143 citations
6. 06*

   Measuring the weak mixing angle with the P2 experiment at MESA

   Niklaus Berger🇩🇪 · Kurt Aulenbacher🇩🇪 · Sebastian Baunack🇩🇪 · Dominik Becker🇩🇪 · Jürgen Diefenbach🇺🇸 · Michael Gericke🇨🇦 · Kathrin Gerz🇩🇪 · Ruth Herbertz🇩🇪 · Krishna Kumar🇺🇸 · Frank Maas🇩🇪 · Matthias Molitor🇩🇪 · David Rodríguez Piñeiro🇩🇪 and 6 other authors

   The P2 experiment in Mainz aims to measure the weak mixing angle in electron- proton scattering to a precision of 0.13 %. In order to suppress uncertainties due to proton structure and contributions from box graphs, both a low average momentum transfer $Q^2$ of $4.5\cdot 10^{-3}$ GeV${}^2/c^2$ and a low beam energy of 155 MeV are chosen. In order to collect the enormous statistics required for this measurement, the new Mainz Energy Recovery Superconducting Accelerator (MESA) is being constructed. These proceedings describe the motivation for the measurement, the experimental and accelerator challenges and how we plan to tackle them.

   ↳ physics.ins-dethep-exnucl-exJ.Univ.Sci.Tech.China(2016)·37 citations
7. 07*

   QCD running in neutrinoless double beta decay: Short-range mechanisms

   M. González🇨🇱 · M. Hirsch🇪🇸 · S.G. Kovalenko🇨🇱

   The decay rate of neutrinoless double beta ($0\nu \beta \beta$) decay contains terms from heavy particle exchange, which lead to dimension-9 (d=9) six fermion operators at low energies. Limits on the coefficients of these operators have been derived previously neglecting the running of the operators between the high-scale, where they are generated, and the energy scale of double beta decay, where they are measured. Here we calculate the leading order QCD corrections to all possible d=9 operators contributing to the $0\nu \beta \beta$ amplitude and use RGE running to calculate 1-loop improved limits. Numerically, QCD running changes limits by factors of the order of or larger than typical uncertainties in nuclear matrix element calculations. For some specific cases, operator mixing in the running changes limits even by up to two orders of magnitude. Our results can be straightforwardly combined with new experimental limits or improved nuclear matrix element calculations to re-derive updated limits on all short-range contributions to $0\nu \beta \beta$ decay.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2016)·41 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.