Tue·Sep 1, 2015Tuesday·September 1, 2015

1. 01*

   Elastic proton scattering at intermediate energies as a probe of the ${}^{6,8}$He nuclear matter densities

   Le Xuan Chung🇻🇳 · Oleg A. Kiselev🇩🇪 · Dao T. Khoa🇻🇳 · Peter Egelhof🇩🇪

   The Glauber model analysis of the elastic ${}^{6,8}$He+$p$ scattering data at energies around 700 MeV/nucleon, measured in two separate experiments at GSI-Darmstadt, has been done using several phenomenological parametrizations of the nuclear matter density. By taking into account the new data points measured at the high momentum transfer, the nuclear matter radii of ${}^{6,8}$He were accurately determined from the Glauber model analysis of the data, with the spin-orbital interaction explicitly taken into account. The well-known geometry for the core and dineutron halo has been used with the new parametrizations of the ${}^6$He density to extract the detailed information on the structure of ${}^6$He in terms of the core and dineutron halo radii. An enhanced sensitivity of the data measured at the high momentum transfer to the core part of the ${}^{6,8}$He densities has been found.

   nucl-exnucl-thPRC(2015)·20 citations
2. 02*

   Does the alpha cluster structure in light nuclei persist through the fusion process?

   J. Vadas🇺🇸 · T.K. Steinbach🇺🇸 · J. Schmidt🇺🇸 · Varinderjit Singh🇺🇸 · C. Haycraft🇺🇸 · S. Hudan🇺🇸 · R.T. deSouza🇺🇸 · L.T. Baby🇺🇸 · S.A. Kuvin🇺🇸 · I. Wiedenhover🇺🇸

   [Background] Despite the importance of light-ion fusion in nucleosynthesis, a limited amount of data exists regarding the de-excitation following fusion for such systems. [Purpose] To explore the characteristics of alpha emission associated with the decay of light fused systems at low excitation energy. [Method] Alpha particles were detected in coincidence with evaporation residues (ER) formed by the fusion of 18O and 12C nuclei. Both alpha particles and ERs were identified on the basis of their energy and time-of-flight. ERs were characterized by their energy spectra and angular distributions while the alpha particles were characterized by their energy spectra, angular distributions, and cross-sections. [Results] While the energy spectra and angular distributions for the alpha particles are well reproduced by statistical model codes, the measured cross-section is substantially underpredicted by the models. Comparison with similar systems reveals that the fundamental quantity for the alpha cross-section is Ec.m. and not the excitation energy of the fused system. [Conclusion]The enhancement in the measured alpha cross-section as compared to the statistical model codes and its dependence with Ec.m. suggest that a coupling between pre-existing alpha cluster structure and the collision dynamics is responsible for the observed alpha cross-section.

   nucl-ex1 citation
3. 03*

   The Nucleon Polarizability Program at MAMI-A2

   G. M. Huber🇨🇦 · C. Collicott🇨🇦

   Low energy Compton scattering allows the investigation of one of the fundamental properties of the nucleon -- how its internal structure deforms under an applied electromagnetic field. We review recent developments in the investigation of proton polarizabilities, and our plans for future measurement at the Mainz Microtron (MAMI).

   nucl-ex11 citations
4. 04*

   The Sensitivity of Core-Collapse Supernovae to Nuclear Electron Capture

   Chris Sullivan · Evan O'Connor🇺🇸 · Remco G. T. Zegers🇺🇸 · Thomas Grubb🇦🇺 · Sam M. Austin🇺🇸

   A weak-rate library aimed at investigating the sensitivity of astrophysical environments to variations of electron-capture rates on medium-heavy nuclei has been developed. With this library, the sensitivity of the core-collapse and early post-bounce phases of core-collapse supernovae to nuclear electron-capture is examined by systematically and statistically varying electron-capture rates of individual nuclei. The rates are adjusted by factors consistent with uncertainties indicated by comparing theoretical rates to those deduced from charge-exchange and $\beta$-decay measurements. To ensure a model independent assessment, sensitivity studies across a comprehensive set of progenitors and equations of state are performed. In our systematic study, we find a +16/-4 % range in the mass of the inner-core at the time of shock formation and a $\pm$20% range of peak {\nu}e-luminosity during the deleptonization burst. These ranges are each five times as large as those seen from a separate progenitor study in which we evaluated the sensitivity of these parameters to 32 presupernova stellar models. It is also found that the simulations are more sensitive to a reduction in the electron-capture rates than an enhancement, and in particular to the reduction in the rates for neutron-rich nuclei near the N = 50 closed neutron-shell. As measurements for medium-heavy (A > 65) and neutron-rich nuclei are sparse, and because accurate theoretical models which account for nuclear structure considerations on the individual nucleus level are not readily available, rates for these nuclei may be overestimated. If more accurate estimates confirm this, results from this study indicate that significant changes to the core-collapse trajectory can be expected. For this reason, experimental and theoretical efforts should focus in this region of the nuclear chart.

   ↳ astro-ph.HEnucl-exnucl-thApJ(2016)·96 citations
5. 05*

   The impact of individual nuclear properties on $r$-process nucleosynthesis

   M. R. Mumpower🇺🇸 · R. Surman🇺🇸 · G. C. McLaughlin🇺🇸 · A. Aprahamian🇺🇸

   The astrophysical rapid neutron capture process or `$r$ process' of nucleosynthesis is believed to be responsible for the production of approximately half the heavy element abundances found in nature. This multifaceted problem remains one of the greatest open challenges in all of physics. Knowledge of nuclear physics properties such as masses, $\beta$-decay and neutron capture rates, as well as $\beta$-delayed neutron emission probabilities are critical inputs that go into calculations of $r$-process nucleosynthesis. While properties of nuclei near stability have been established, much still remains unknown regarding neutron-rich nuclei far from stability that may participate in the $r$ process. Sensitivity studies gauge the astrophysical response of a change in nuclear physics input(s) which allows for the isolation of the most important nuclear properties that shape the final abundances observed in nature. This review summarizes the extent of recent sensitivity studies and highlights how these studies play a key role in facilitating new insight into the $r$ process. The development of these tools promotes a focused effort for state-of-the-art measurements, motivates construction of new facilities and will ultimately move the community towards addressing the grand challenge of `How were the elements from iron to uranium made?'.

   ↳ nucl-thastro-ph.SRnucl-exPPNP(2016)·478 citations
6. 06*

   Reconstruction of hit-time and hit-position of annihilation quanta in the J-PET detector using the Mahalanobis distance

   N. G. Sharma🇵🇱 · M. Silarski🇵🇱 · T. Bednarski🇵🇱 · P. Białas🇵🇱 · E. Czerwiński🇵🇱 · A. Gajos🇵🇱 · M. Gorgol🇵🇱 · B. Jasińska🇵🇱 · D. Kamińska🇵🇱 · Ł. Kapłon🇵🇱 · G. Korcyl🇵🇱 · P. Kowalski🇵🇱 and 15 other authors

   The J-PET detector being developed at Jagiellonian University, is a Positron Emission Tomograph composed of the long strips of polymer scintillators. At the same time it is a detector system which will be used for studies of the decays of positronium atoms. The shape of photomultiplier signals depends on the hit-time and hit-position of the gamma quantum. In order to take advantage of this fact a dedicated sampling front-end electronics which enables to sample signals in voltage domain with the time precision of about 20 ps and novel reconstruction method based on the comparison of examined signal with the model signals stored in the library has been developed. As a measure of the similarity we use the Mahalanobis distance. The achievable position and time-resolution depends on number and values of the threshold levels at which the signal is sampled. A reconstruction method, as well as preliminary results are presented and discussed.

   ↳ physics.ins-detnucl-exNukleonika(2015)·10 citations
7. 07*

   Forward $D$ predictions for $p\mathrm{Pb}$ collisions, and sensitivity to cold nuclear matter effects

   Rhorry Gauld🇬🇧

   Predictions are provided for double differential cross sections and forward-backward ratios of $D^0$ production in $p\mathrm{Pb}$ (forward) and $\mathrm{Pb}$$p$ (backward) collisions at 5.02~TeV. The effect of nuclear corrections on the ratio of differential cross sections ratios is estimated to be $\simeq$ (10-30)\% in the kinematically accessible region of LHCb, and interestingly this ratio is approximately flat with respect to $p_T(D^0)$ due to a compensation of shadowing and anti-shadowing effects arising from the input nuclear PDFs. In comparison to $J/\psi (\to {\mu }^{-}{\mu }^{+})$ measurements which have already been performed with the available data, the cross section for $D^0(\to K^{-}{\pi }^{+})$ production is expected to be two-orders of magnitude higher.

   ↳ hep-phhep-exnucl-exPRD(2016)·18 citations
8. 08*

   Possibility of DCC formation in pp collisions at LHC energy via reaction-diffusion equation

   Partha Bagchi🇮🇳 · Arpan Das🇮🇳 · Srikumar Sengupta🇮🇳 · Ajit M. Srivastava🇮🇳

   There are indications of formation of a thermalized medium in high multiplicity pp collisions at LHC energy. It is possible that such a medium may reach high enough energy density/temperature so that a transient stage of quark-gluon plasma, where chiral symmetry is restored, may be achieved. Due to rapid 3-dimensional expansion, the system will quickly cool undergoing spontaneous chiral symmetry breaking transition. We study the dynamics of chiral field, after the symmetry breaking transition, for such an event using reaction-diffusion equation approach which we have recently applied for studying QCD transitions in relativistic heavy-ion collisions. We show that the interior of such a rapidly expanding system is likely to lead to the formation of a single large domain of disoriented chiral condensate (DCC) which has been a subject of intensive search in earlier experiments. We argue that large multiplicity pp collisions naturally give rise to required boundary conditions for the existence of slowly propagating front solutions of reaction-diffusion equation with resulting dynamics of chiral field leading to the formation of a large DCC domain.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2016)·1 citation
9. 09*

   Single Freeze-Out, Statistics and Pion, Kaon and Proton Production in Central Pb-Pb Collisions at $\sqrt{s_{NN}}=2.76$ TeV

   Dariusz Prorok🇵🇱

   Many data in the high energy physics are, in fact, sample means. It is shown that when this exact meaning of the data is taken into account and the most weakly bound states are removed from the hadron resonance gas, the acceptable fit to the whole spectra of pions, kaons and protons measured at midrapidity in central Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV [Phys.Rev.Lett.109,252301(2012)] is obtained. The invariant distributions are predicted with the help of the single-freeze-out model in the chemical equilibrium framework. Low $p_T$ pions and protons are reproduced simultaneously as well as $p/\pi$ ratio. Additionally, correct predictions extend over lower parts of large $p_T$ data. Some more general, possible implications of this approach are pointed out.

   ↳ nucl-thhep-exhep-phnucl-exJ.Phys.G(2016)·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.