Tue·Mar 17, 2015Tuesday·March 17, 2015

1. 01*

   The $\varphi (1020)\to e^{+}{e}^{-}$ meson decay measured with the STAR experiment in Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV

   STAR Collaboration: L. Adamczyk🇵🇱 · J. K. Adkins🇺🇸 · G. Agakishiev🇷🇺 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · I. Alekseev🇷🇺 · A. Aparin🇷🇺 · D. Arkhipkin🇺🇸 · E. C. Aschenauer🇺🇸 · M. U. Ashraf · A. Attri · G. S. Averichev🇷🇺 and 326 other authors

   We report the measurement of the leptonic ($e^{+}{e}^{-}$) decay channel of the $\varphi$(1020) meson in Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV by the STAR experiment. The transverse momentum ($p_{\mathrm{T}}$) spectrum is measured for 0.1 $\le p_{\mathrm{T}}\le 2.5$ GeV/$c$ at mid-rapidity ($|y|\le 1$). We obtain the $p_{\mathrm{T}}$-integrated $\varphi$(1020) mass $M_{\varphi }=1017.7\pm 0.8(stat.)\pm 0.9(sys.)$ MeV/$c^2$ and width ${\Gamma }_{\varphi }=8.0\pm 2.5(stat.)\pm 2.3(sys.)\text{MeV/}{\mathrm{c}}^2$, which are within 1.5\,$\sigma$ and 1.1\,$\sigma$ of the vacuum values, respectively. No significant difference is observed in the measured $p_{\mathrm{T}}$ spectrum, $dN/dy$, or $⟨p_{\mathrm{T}}⟩$ of the $\varphi$(1020) meson between the $e^{+}{e}^{-}$ and hadronic ($K^{+}{K}^{-}$) decay channels as measured by the same experiment. The experimental results are compared to a theoretical model including medium-modified $\varphi$(1020).

   ↳ hep-exnucl-ex1 citation
2. 02*

   Alpha cluster structures and monopole excitations in ${}^{13}$C

   Taiichi Yamada🇯🇵 · Yasuro Funaki🇯🇵

   The structure of $1/2^{\pm }$ states in ${}^{13}$C up to around the $3\alpha +n$ threshold ($E_x=12.3$~MeV) is investigated with a full four-body $3\alpha +n$ orthogonality condition model (OCM) calculation, where the $3\alpha$ OCM, the model space of which is the subspace of the $3\alpha +n$ model, describes well the structure of the low-lying states of ${}^{12}$C including the $2_2^{+}$, $0_3^{+}$, and $0_4^{+}$ states, which have been recently observed above the Hoyle state ($0_2^{+}$). A full spectrum up to the $1/2_5^{-}$ ($1/2_3^{+}$) state is reproduced consistently with the lowest five $1/2^{-}$ (three $1/2^{+}$) states of experimental spectrum. It is shown that the $1/2_2^{-}$ and $1/2_3^{-}$ states are characterized by the dominant cluster configurations of ${}^9$Be($3/2^{-}$,$1/2^{-}$)+$\alpha$, while the ground state $1/2_1^{-}$ has a shell-model-like structure. The observed monopole transition strengths to the $1/2_{2,3}^{-}$ states are consistently reproduced for the first time. These results indicate that the excited $1/2^{-}$ states have cluster structures. They are compared to those by the previous work with the shell model. On the other hand, the $1/2_1^{+}$ state is found to have a loosely bound neutron structure in which the extra neutron moves around ${}^{12}$C(g.s) core with $1S$ orbit, reflecting the fact that this state appears by $1.9$ MeV just below the ${}^{12}$C(g.s)+$n$ threshold, while the $1/2_2^{+}$ and $1/2_3^{+}$ states are characterized by ${}^9$Be+$\alpha$ structures. We found that the $1/2_5^{+}$ state located above the $3\alpha +n$ threshold is the Hoyle analogue state in ${}^{13}$C, the wave function of which is described by product states of constituent clusters, $(0S{)}_{\alpha }^3(S{)}_n$, with the probability of $52$ %.

   ↳ nucl-thnucl-exPRC(2015)·56 citations
3. 03*

   Spectrum of resonance states in ${}^6$He. Experimental and theoretical analysis

   O. M. Povoroznyk🇺🇦 · V. S. Vasilevsky

   We explore the structure of resonance states in ${}^6$He by experimental and theoretical methods. We present the results of experimental investigations of the three-body continuous spectrum of ${}^6$He. For this aim, we use the reaction ${}^3$H$(\alpha ,p\alpha )nn$, which is induced by the interaction of alpha-particles with a triton at the beam energy $E_{\alpha }=$~67.2 MeV. The theoretical analysis of the resonance structure in ${}^6$He is carried out within the framework of a three-cluster microscopic model. The model exploits the hyperspherical harmonics to describe the intercluster dynamics. The set of new resonance states is discovered by the experimental and theoretical methods. The energy, width, and dominant decay channels of resonances are determined.The obtained results are compared in detail with the results of different theoretical models and experiments as well.

   ↳ nucl-thnucl-exUkr.J.Phys.(2015)·4 citations
4. 04*

   Enhancement of the CP-odd effect in the nuclear electric dipole moment of ${}^6$Li

   Nodoka Yamanaka🇯🇵 · Emiko Hiyama🇯🇵

   We calculate for the first time the electric dipole moment (EDM) of the ${}^6$Li nucleus within the alpha + p + n three-body cluster model using the Gaussian expansion method, assuming the one meson exchange P, CP-odd nuclear forces. It is found that the EDM of the ${}^6$Li is 2 times more sensitive on the isovector pion exchange P, CP-odd nuclear force than the deuteron EDM, due to the CP-odd interaction between the nucleons and the alpha cluster. The ${}^9$Be EDM is also calculated in the same framework as an alpha + alpha + n three-body system. We also test the ab initio calculation of the EDM of the deuteron, ${}^3$H and ${}^3$He nuclei using the realistic Argonne $v18$ nuclear force. In the ab initio calculations, good agreements with previous studies are obtained. We finally discuss the prospects for the new physics beyond the standard model.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2015)·59 citations
5. 05*

   Search for octupole correlations in ${}^{147}$Nd

   E. Ruchowska · H. Mach🇪🇸 · M. Kowal🇵🇱 · J. Skalski🇵🇱 · W. A. Plociennik · B. Fogelberg

   Properties of excited states in ${}^{147}$Nd have been studied with multispectra and $\gamma \gamma$ coincidence measurements. Twenty-four new $\gamma$-lines and three new levels have been introduced into the level scheme of ${}^{147}$Nd. Lifetimes of eight excited levels in ${}^{147}$Nd, populated in the $\beta$ decay of ${}^{147}$Pr, have been measured using the advanced time-delayed $\beta \gamma \gamma$(t) method. Reduced transition probabilities have been determined for 30 $\gamma$-transitions in ${}^{147}$Nd. Potential energy surfaces on the (${\beta }_2$,${\beta }_3$) plane calculated for ${}^{147}$Nd using the Strutinsky method predict two single quasiparticle configurations with nonzero octupole deformation, with K=1/2 and K=5/2. We do not observe parity doublet bands with K=5/2. For pair of opposite parity bands that could form the K=1/2 parity doublet we were able only to determine lower limit of the dipole moment, $|D_0|\ge$0.02 e$\cdot fm$.

   ↳ nucl-thnucl-exPRC(2015)·9 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.