Wed·Dec 18, 2019Wednesday·December 18, 2019

1. 01*

   Shell evolution of $N=40$ isotones towards ${}^{60}$Ca: First spectroscopy of ${}^{62}$Ti

   M. L. Cortés🇯🇵 · W. Rodriguez🇨🇴 · P. Doornenbal🇯🇵 · A. Obertelli🇫🇷 · J. D. Holt🇨🇦 · S. M. Lenzi🇮🇹 · J. Menéndez🇯🇵 · F. Nowacki🇫🇷 · K. Ogata🇯🇵 · A. Poves🇪🇸 · T. R. Rodríguez🇪🇸 · A. Schwenk🇩🇪 and 72 other authors

   Excited states in the $N=40$ isotone ${}^{62}$Ti were populated via the ${}^{63}$V$(p,2p)$${}^{62}$Ti reaction at $\sim$200~MeV/u at the Radioactive Isotope Beam Factory and studied using $\gamma$-ray spectroscopy. The energies of the $2_1^{+}\to 0_{\mathrm{gs}}^{+}$ and $4_1^{+}\to 2_1^{+}$ transitions, observed here for the first time, indicate a deformed ${}^{62}$Ti ground state. These energies are increased compared to the neighboring ${}^{64}$Cr and ${}^{66}$Fe isotones, suggesting a small decrease of quadrupole collectivity. The present measurement is well reproduced by large-scale shell-model calculations based on effective interactions, while ab initio and beyond mean-field calculations do not yet reproduce our findings. The shell-model calculations for ${}^{62}$Ti show a dominant configuration with four neutrons excited across the $N=40$ gap. Likewise, they indicate that the $N=40$ island of inversion extends down to $Z=20$, disfavoring a possible doubly magic character of the elusive ${}^{60}$Ca.

   nucl-exnucl-thPLB(2020)·49 citations
2. 02*

   Underlying event measurements in $p$+$p$ collisions at $\sqrt{s}=200$ GeV at RHIC

   STAR Collaboration: J. Adam🇺🇸 · L. Adamczyk🇵🇱 · J. R. Adams🇺🇸 · J. K. Adkins🇺🇸 · G. Agakishiev🇷🇺 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · I. Alekseev🇷🇺 · D. M. Anderson🇺🇸 · A. Aparin🇷🇺 · E. C. Aschenauer🇺🇸 · M. U. Ashraf🇨🇳 and 346 other authors

   Particle production sensitive to non-factorizable and non-perturbative processes that contribute to the underlying event associated with a high transverse momentum ($p_T$) jet in proton+proton collisions at $\sqrt{s}$=200 GeV is studied with the STAR detector. Each event is divided into three regions based on the azimuthal angle with respect to the highest-$p_T$ jet direction: in the leading jet direction ("Toward"), opposite to the leading jet ("Away"), and perpendicular to the leading jet ("Transverse"). In the Transverse region, the average charged particle density is found to be between 0.4 and 0.6 and the mean transverse momentum, $⟨p_T⟩$, between 0.5-0.7 GeV/$c$ for particles with $p_T$$>$0.2 GeV/$c$ at mid-pseudorapidity ($|\eta |$$<$1) and jet $p_T$$>$15 GeV/$c$. Both average particle density and $⟨p_T⟩$ depend weakly on the leading jet $p_T$. Closer inspection of the Transverse region hints that contributions to the underlying event from initial- and final-state radiation are significantly smaller in these collisions than at the higher energies, up to 13 TeV, recorded at the LHC. Underlying event measurements associated with a high-$p_T$ jet will contribute to our understanding of QCD processes at hard and soft scales at RHIC energies, as well as provide constraints to modeling of underlying event dynamics.

   nucl-exhep-exPRD(2020)·29 citations
3. 03*

   A Functional Form for Liquid Scintillator Pulse Shapes

   F.Q.L Friesen · C.R. Howell🇺🇸

   Digitization of detector signals enables analysis of the original waveform to extract timing, particle identification, and energy deposition information. Here we present the use of analytical functions based on sigmoids to model and fit such pulse shapes from liquid organic scintillators, though the method should also be applicable to other detector systems. Neutron and gamma interactions in NE213 detectors were digitized from the phototube anode and fit using a sigmoid-based function. The acuity of the fit in extracting timing information and performing neutron-gamma pulse-shape discrimination are presented and discussed.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2020)·0 citations
4. 04*

   Global Polarization Effect in the Extremely Rapidly Rotating QGP in HIC

   Zuo-Tang Liang🇨🇳 · Michael Annan Lisa🇺🇸 · Xin-Nian Wang🇨🇳

   This is prepared for a featured article in Nuclear Physics News. Recently, the global polarization of \Lambda and \bar{\Lambda} hyperons in heavy-ion collisions (HIC) has been observed by the STAR Collaboration at the Relativistic Heavy Ion Collider in Brookhaven National Laboratory. The discovery confirms the theoretical prediction made more than ten years ago and indicates that the quark gluon plasma (QGP) produced in HIC possesses a vorticity as high as 10^21s^-1, much higher than any other fluid observed in nature. This opens a new window to study properties of QGP and a new direction in high energy heavy ion physics. This featured article is aimed to report the basic idea, current status and outlook.

   ↳ nucl-thnucl-exNucl.Phys.News(2020)·22 citations
5. 05*

   A global perspective on searches for Electric Dipole Moments

   Guillaume Pignol🇫🇷

   Many experiments are underway in the world to search for a non-zero electric dipole moment (EDM) of a particle with spin 1/2 such as the neutron or the electron. Finding an EDM would reveal new sources of CP violation. EDM measurements are motivated by the high sensitivity to new physics beyond the Standard Model. They are relevant to find the explanation for the matter-antimatter asymmetry of the Universe. A variety of programs with different systems are being pursued, with free neutrons, diamagnetic atoms, paramagnetic systems, and charged particles in storage rings. This article presents a basic introduction of the subject and attempts to compile the ongoing projects.

   ↳ hep-phhep-exnucl-ex2 citations
6. 06*

   Storage Ring to Search for Electric Dipole Moments of Charged Particles -- Feasibility Study

   F. Abusaif · A. Aggarwal · A. Aksentev · B. Alberdi-Esuain · A. Andres · A. Atanasov · L. Barion · S. Basile · M. Berz · C. Böhme · J. Böker · J. Borburgh and 89 other authors

   The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly ${}^3$He) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities could approach 10${}^{-29}$ e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarisation, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarisation from the longitudinal to the vertical direction. The slow rise in the vertical polarisation component, detected through scattering from a target, signals the EDM. The project strategy is outlined. A stepwise plan is foreseen, starting with ongoing COSY activities that demonstrate technical feasibility. Achievements to date include reduced polarization measurement errors, long horizontal plane polarization lifetimes, and control of the polarization direction through feedback from scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally a high-precision electric-field storage ring.

   ↳ hep-exnucl-exphysics.acc-phCERN Yellow Rep.Monogr.(2021)·83 citations
7. 07*

   Probing the Sivers function with an unpolarized target: GTMD distributions and the Odderons

   Renaud Boussarie🇺🇸 · Yoshitaka Hatta🇺🇸 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷

   It is commonly believed that the Sivers function has uniquely to do with processes involving a transversely polarized nucleon. In this paper we show that it is not necessarily the case. We demonstrate that exclusive pion production in $un$polarized electron-proton scattering in the forward region is a direct probe of the gluon Sivers function due to its connection to the QCD Odderon.

   ↳ hep-phhep-exnucl-exnucl-thPRL(2020)·49 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.