Fri·Apr 23, 2021Friday·April 23, 2021

1. 01*

   Neutron-proton pairing in the N=Z radioactive fp-shell nuclei 56Ni and 52Fe probed by pair transfer

   B. Le Crom🇫🇷 · M. Assié🇫🇷 · Y. Blumenfeld🇫🇷 · J. Guillot🇫🇷 · H. Sagawa🇯🇵 · T. Suzuki🇯🇵 · M. Honma🇯🇵 · N.L. Achouri🇫🇷 · B. Bastin🇫🇷 · R. Borcea🇷🇴 · W.N. Catford🇬🇧 · E. Clement🇫🇷 and 40 other authors

   The isovector and isoscalar components of neutron-proton pairing are investigated in the N=Z unstable nuclei of the \textit{fp}-shell through the two-nucleon transfer reaction (p,${}^3$He) in inverse kinematics. The combination of particle and gamma-ray detection with radioactive beams of ${}^{56}$Ni and ${}^{52}$Fe, produced by fragmentation at the GANIL/LISE facility, made it possible to carry out this study for the first time in a closed and an open-shell nucleus in the \textit{fp}-shell. The transfer cross-sections for ground-state to ground-state (J=0${}^{+}$,T=1) and to the first (J=1${}^{+}$,T=0) state were extracted for both cases together with the transfer cross-section ratios $\sigma$(0${}^{+}$,T=1) /$\sigma$(1${}^{+}$,T=0). They are compared with second-order distorted-wave born approximation (DWBA) calculations. The enhancement of the ground-state to ground-state pair transfer cross-section close to mid-shell, in ${}^{52}$Fe, points towards a superfluid phase in the isovector channel. For the "deuteron-like" transfer, very low cross-sections to the first (J=1${}^{+}$,T=0) state were observed both for \Ni\phe\, and \Fe\phe\, and are related to a strong hindrance of this channel due to spin-orbit effect. No evidence for an isoscalar deuteron-like condensate is observed.

   nucl-exPLB(2022)·10 citations
2. 02*

   Heavy-flavour studies with a high-luminosity fixed-target experiment at the LHC

   B.Trzeciak🇨🇿 · S.J. Brodsky🇺🇸 · G. Cavoto🇮🇹 · C. Da Silva🇺🇸 · M.G. Echevarria🇪🇸 · E.G. Ferreiro🇪🇸 · C. Hadjidakis🇫🇷 · R. Haque🇵🇱 · I. Hrivnacova🇫🇷 · D. Kikola🇵🇱 · A. Klein🇺🇸 · A. Kurepin🇷🇺 and 22 other authors

   Extraction of the multi-TeV proton and lead LHC beams with a bent crystal or by using an internal gas target allows one to perform the most energetic fixed-target experiment ever. pp, pd and pA collisions at $\sqrt{s}$ = 115 GeV and Pbp and PbA collisions at $\sqrt{s_{\mathrm{NN}}}$ = 72 GeV can be studied with high precision and modern detection techniques over a broad rapidity range. Using the LHCb or the ALICE detector in a fixed-target mode offers unprecedented possibilities to access heavy-flavour production in a new energy domain, half way between the SPS and the nominal RHIC energy. In this contribution, a review of projection studies for quarkonium and open charm and beauty production with both detector set-ups used with various nuclear targets and the LHC lead beams is presented.

   nucl-exPoS(2021)·1 citation
3. 03*

   Quenching of heavy and light flavour jets: experimental overview

   Barbara Trzeciak🇨🇿

   In these proceedings, recent experimental results on jet quenching are discussed, focusing on measurements shown at the Quark Matter 2019 conference.

   nucl-exhep-exNPA(2021)·1 citation
4. 04*

   The MUGAST-AGATA-VAMOS campaign : set-up and performance

   M. Assié · E. Clément · A. Lemasson · D. Ramos · A. Raggio · I. Zanon · F. Galtarossa · C. Lenain · J. Casal · F. Flavigny · A. Matta · D. Mengoni and 37 other authors

   The MUGAST-AGATA-VAMOS set-up at GANIL combines the MUGAST highly-segmented silicon array with the state-of-the-art AGATA array and the large acceptance VAMOS spectrometer. The mechanical and electronics integration copes with the constraints of maximum efficiency for each device, in particular {\gamma}-ray transparency for the silicon array. This complete set-up offers a unique opportunity to perform exclusive measurements of direct reactions with the radioactive beams from the SPIRAL1 facility. The performance of the set-up is described through its commissioning and two examples of transfer reactions measured during the campaign. High accuracy spectroscopy of the nuclei of interest, including cross-sections and angular distributions, is achieved through the triple-coincidence measurement. In addition, the correction from Doppler effect of the {\gamma}-ray energies is improved by the detection of the light particles and the use of two-body kinematics and a full rejection of the background contributions is obtained through the identification of heavy residues. Moreover, the system can handle high intensity beams (up to 108 pps). The particle identification based on the measurement of the time-of-flight between MUGAST and VAMOS and the reconstruction of the trajectories is investigated.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2021)·26 citations
5. 05*

   Electric dipole polarizability of neutron rich nuclei

   J. Piekarewicz🇺🇸

   Insights into the equation of state of neutron rich matter obtained from the neutron skin thickness of 208Pb are in sharp conflict with earlier measurements of the electric dipole polarizability. We use a set of accurately calibrated energy density functionals to highlight the tension and to articulate how plans for a highly-intense Gamma Factory may alleviate the tension.

   ↳ nucl-thnucl-exAnnalen Phys.(2022)·1 citation
6. 06*

   Theoretical description of the neutron beta decay in the standard model at the level of 10^{-5}

   A. N. Ivanov🇦🇹 · R. Höllwieser🇩🇪 · N. I. Troitskaya🇦🇹 · M. Wellenzohn🇦🇹 · Ya. A. Berdnkov🇷🇺

   In the framework of the Standard Model (SM) a theoretical description of the neutron beta decay is given at the level of 10^{-5}. The neutron lifetime and correlation coefficients of the neutron beta decay for a polarized neutron, a polarized electron and an unpolarized proton are calculated at the account for i) the radiative corrections of order O(\alpha E_e/m_N) ~ 10^{-5} to Sirlin's outer and inner radiative corrections of order O(\alpha/\pi), ii) the corrections of order O(E^2_e/m^2_N) ~ 10^{-5}, caused by weak magnetism and proton recoil, and iii) Wilkinson's corrections of order 10^{-5} (Wilkinson, Nucl. Phys. A377, 474 (1982)). These corrections define the SM background of the theoretical description of the neutron beta decay at the level of 10^{-5}, which is required by experimental searches of interactions beyond the SM with experimental uncertainties of a few parts of 10^{-5}.

   ↳ hep-phnucl-exnucl-thPRD(2021)·9 citations
7. 07*

   Color Transparency and the Proton Form Factor- Feynman Wins

   Olivia Caplow-Munro🇺🇸 · Gerald A. Miller🇺🇸

   A recent experiment [{\bf Phys. Rev. Lett. 126,082301 (2021)}] used the $(e,e^{\prime }p)$ reaction on ${}^{12}$C to search for the effects of color transparency (the absence of final state interactions). Color transparency was said to be ruled out. The ability to observe the effects of color transparency depends on the ability of a putative point-like-configuration (PLC), formed in a high-momentum transfer coherent reaction, to escape the nucleus without expanding its size. We study the expansion aspect of color transparency using superconformal baryon-meson symmetry and light-front holographic QCD. A new formalism is obtained and used to analyze the recent experiment. The resulting conclusion is that effects of expansion would not be sufficiently significant in causing final state interactions to occur. Therefore we conclude that a PLC was not formed. This means that the Feynman mechanism involving virtual photon absorption on a single high momentum quark is responsible for high momentum electromagnetic form factor of the proton.

   ↳ nucl-thhep-phnucl-exPRC(2021)·17 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.