Fri·Dec 25, 2015Friday·December 25, 2015

1. 01*

   Charmonium production in Pb-Pb collisions with ALICE at the LHC

   H. Pereira Da Costa (for the ALICE Collaboration)🇫🇷

   We report on published charmonium measurements performed by ALICE, at the LHC, in Pb-Pb collisions at a center of mass energy per nucleon-nucleon collision $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV, at both mid ($|y|<0.8$) and forward ($2.5<y<4$) rapidities. The nuclear modification factor of inclusive $\mathrm{J}/\psi$ is presented as a function of the collision centrality and the $\mathrm{J}/\psi$ transverse momentum, $p_{\mathrm{T}}$. The variation of the $\mathrm{J}/\psi$ mean transverse momentum square as a function of the collision centrality is also discussed. These measurements are compared to state of the art models that include one or several of the following mechanisms: color screening of the charm quarks, statistical hadronization at the QGP phase boundary, balance between $\mathrm{J}/\psi$ dissociation and regeneration in the QGP, $\mathrm{J}/\psi$ interaction with a dense comoving medium. Results on the production of the heavier and less bound ${\psi }^{\prime }$ meson in Pb-Pb collisions at forward-rapidity are also presented and compared to both models and measurements performed by other experiments. At mid-rapidity we also report on ALICE unique capability to separate prompt and non-prompt $\mathrm{J}/\psi$ production down to low $p_{\mathrm{T}}$ ($\ge 1.5$ GeV/$c$) and thus disentangle between effects on prompt $\mathrm{J}/\psi$ mesons and energy loss of $b$ quarks in the QGP.

   nucl-exNPA(2016)·3 citations
2. 02*

   Hypernuclei in Halo/Cluster Effective Field Theory

   Shung-Ichi Ando (Sunmoon U.)🇰🇷

   The light double $\Lambda$ hypernuclei, ${}_{\Lambda \Lambda }^4$H and ${}_{\Lambda \Lambda }^6$He, are studied as three-body $\Lambda \Lambda d$ and $\Lambda \Lambda \alpha$ cluster systems in halo/cluster effective field theory at leading order. We find that the $\Lambda \Lambda d$ system in spin-0 channel does not exhibit a limit cycle whereas the $\Lambda \Lambda d$ system in spin-1 channel and the $\Lambda \Lambda \alpha$ system in spin-0 channel do. The limit cycle is associated with the formation of bound states, known as Efimov states, in the unitary limit. For the $\Lambda \Lambda d$ system in the spin-0 channel we estimate the scattering length $a_0$ for $S$-wave $\Lambda$ hyperon-hypertriton scattering as $a_0=16.0\pm 3.0$ fm. We also discuss that studying the cutoff dependences in the $\Lambda \Lambda d$ and $\Lambda \Lambda \alpha$ systems, the bound state of ${}_{\Lambda \Lambda }^4$H is not an Efimov state but formed due to a high energy mechanism whereas that of ${}_{\Lambda \Lambda }^6$He may be regarded as an Efimov state.

   ↳ nucl-thhep-phnucl-exIJMPE(2016)·8 citations
3. 03*

   Application of the EXtrapolated Efficiency Method (EXEM) to infer the gamma-cascade detection efficiency in the actinide region

   Q. Ducasse🇫🇷 · B. Jurado🇫🇷 · L. Mathieu🇫🇷 · P. Marini🇫🇷 · B. Morillon🇫🇷 · M. Aiche🇫🇷 · I. Tsekhanovich🇫🇷

   The study of transfer-induced gamma-decay probabilities is very useful for understanding the surrogate-reaction method and, more generally, for constraining statistical-model calculations. One of the main difficulties in the measurement of gamma-decay probabilities is the determination of the gamma-cascade detection efficiency. In [Nucl. Instrum. Meth. A 700, 59 (2013)] we developed the Extrapolated Efficiency Method (EXEM), a new method to measure this quantity. In this work, we have applied, for the first time, the EXEM to infer the gamma-cascade detection efficiency in the actinide region. In particular, we have considered the 238U(d,p)239U and 238U(3He,d)239Np reactions. We have performed Hauser-Feshbach calculations to interpret our results and to verify the hypothesis on which the EXEM is based. The determination of fission and gamma-decay probabilities of 239Np below the neutron separation energy allowed us to validate the EXEM.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2016)·2 citations
4. 04*

   Unified description of rotational-, $\gamma$-, and quasiparticle-band structures in neutron-rich mass $\sim$ 110 region

   G. H. Bhat🇮🇳 · J. A. Sheikh · Y. Sun🇨🇳 · R. Palit🇮🇳

   Band structures of the neutron-rich Mo- and Ru-isotopes around A $\sim$ 110 are investigated using the triaxial projected shell model (TPSM) approach employing multi-quasiparticle configuration space. The mass region under investigation depicts a rich variety of band structures with well developed $\gamma$- and $\gamma \gamma$-bands, and quasiparticle excitations based on them. It is demonstrated that TPSM provides a reasonable description of most of the observed properties, in particular, detailed structure variations observed in Mo-isotopes are well reproduced in the present work.

   ↳ nucl-thnucl-exNPA(2016)·19 citations
5. 05*

   Use of the Meta-analysis and Kolmogorov Criteria in the Finding of Singularities of a Nuclear Matter Created in Ultra Relativistic Nuclear Collisions

   V.A. Kizka🇺🇦

   Published theoretical data from several models: PHSD and HSD both with and without chiral symmetry restoration (CSR), applied to experimental data on nuclear collisions from BEVALAC and SIS to LHC energies were analyzed using meta-analysis and Kolmogorov criteria. This made it possible to localize possible features of nuclear matter created in central nucleus-nucleus collisions. Ignition of a drop of quark-gluon plasma (QGP) begins already at an energy of about $\sqrt{s_{NN}}$ = 2 GeV. We estimate that this QGP droplet occupies a small fraction, 15 $\%$ (average radius of about 5.3 fermi if the fireball radius is 10 fermi) of the total volume of the fireball created at $\sqrt{s_{NN}}$ = 2.7 GeV. A drop of exotic matter undergoes a split phase transition: separated boundaries of sharp (1st order) crossover and CSR in chiral limit, between QGP and Quarkyonic matter at an energy about $\sqrt{s_{NN}}$ = 3.5 GeV. The critical endpoint of 2nd order probably cannot be reached in nuclear collisions. The triple phase area occupies interval from $\sqrt{s_{NN}}$ = 12 GeV to 15 GeV, the critical endpoint of 1st order at around $\sqrt{s_{NN}}$ = 20 GeV. The boundary of smooth (2nd order) crossover transition with CSR in chiral limit between Quarkyonic matter and QGP was localized between $\sqrt{s_{NN}}$ = 9.3 GeV and 12 GeV, and between Hadronic and QGP in the interval from $\sqrt{s_{NN}}$ = 15 GeV to 20 GeV, the boundary of sharp (1st order) crossover transition with CSR in chiral limit between Hadronic matter and QGP was localized after $\sqrt{s_{NN}}$ = 20 GeV. The phase trajectory of the hadronic corona, enveloping the exotic droplet, always remains in the hadronic phase.

   ↳ nucl-thastro-ph.HEhep-phnucl-exScience(2024)·1 citation
6. 06*

   Final-state interactions in two-nucleon knockout reactions

   Camille Colle🇧🇪 · Wim Cosyn🇧🇪 · Jan Ryckebusch🇧🇪

   Background: Exclusive two-nucleon knockout after electroexcitation of nuclei ($A(e,e^{\prime }NN)$ in brief) is considered to be a primary source of information about short-range correlations (SRC) in nuclei. For a proper interpretation of the data, final-state interactions (FSI) need to be theoretically controlled. Purpose: Our goal is to quantify the role of FSI effects in exclusive $A(e,e^{\prime }pN)$ reactions for four target nuclei representative for the whole mass region. Our focus is on processes that are SRC driven. We investigate the role of FSI for two characteristic detector setups corresponding with a "small" and "large" coverage of the available phase space. Results: The transparency $T_A^{pN}$, defined as the ratio of exclusive $(e,e^{\prime }pN)$ cross sections on nuclei to those on "free" nucleon pairs, drops from $0.2-0.3$ for ${}^{12}$C to $0.04-0.07$ for ${}^{208}$Pb. For all considered kinematics, the mass dependence of the $T_A^{pN}$ can be captured by the power law $T_A^{pN}\propto A^{-\lambda }$ with $0.4\lesssim \lambda \lesssim 0.5$. Apart from an overall reduction factor, we find that FSI only modestly affects the distinct features of SRC-driven $A(e,e^{\prime }pN)$ which are dictated by the c.m. distribution of close-proximity pairs. Conclusion: The SCX mechanisms represent a relatively small (order of a few percent) contribution of SRC-driven $A(e,e^{\prime }pN)$ processes. The mass dependence of FSI effects in exclusive $A(e,e^{\prime }pN)$ can be captured in a robust power law and is in agreement with the predictions obtained in a toy model.

   ↳ nucl-thnucl-exPRC(2016)·27 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.