Wed·Mar 10, 2021Wednesday·March 10, 2021

1. 01*

   Comparison of Methods for Elliptic Flow Measurements at NICA Energies $\sqrt{s_{NN}}$ = 4-11 GeV

   Vinh Ba Luong🇷🇺 · Dim Idrisov🇷🇺 · Petr Parfenov🇷🇺 · Arkadiy Taranenko🇷🇺 · Alexander Demanov🇷🇺

   The goal of the Multi-Purpose Detector (MPD) experiment at NICA collider is to explore the QCD phase diagram of strongly interacting matter produced in nucleus-nucleus collisions at $\sqrt{s_{NN}}=4-11$ GeV. The performance of MPD detector for elliptic flow measurements of charged hadrons is studied with Monte-Carlo simulations using collisions of Au+Au ions employing UrQMD, SMASH, and AMPT heavy-ion event generators. Different methods for flow measurements: event plane and direct cumulants are used to investigate the contribution of non-flow correlations and flow fluctuations.

   nucl-exhep-exAIP Conf.Proc.(2021)·2 citations
2. 02*

   Target-Normal Single Spin Asymmetries Measured with Positrons

   G. N. Grauvogel🇺🇸 · T. Kutz🇺🇸 · A. Schmidt🇺🇸

   Two-photon exchange and the larger class of hadronic box diagrams are difficult to calculate without a large degree of model-dependence. At the same time, these processes are significant radiative corrections in parity-violating electron scattering, in neutron decay, and may even be responsible for the proton's form factor ratio discrepancy. New kinds of experimental data are needed to help constrain models and guide future box-diagram calculations. The target-normal single spin asymmetry, $A_n$, formed with an unpolarized beam scattering from a target that is polarized normal to the scattering plane, is sensitive to the imaginary part of the two-photon exchange amplitude, and can provide a valuable constraint. A measurement with both electrons and positrons can reduce sources of experimental error, and distinguish between the effects of two-photon exchange and those of time-reversal symmetry violation. This article describes a proposed experiment in Hall A, using the new Super Big-Bite Spectrometer that can cover a momentum transfer range in the critical zone of uncertainty between where hadronic calculations and those based on partonic degrees of freedom are expected to be accurate.

   nucl-exEPJA(2021)·9 citations
3. 03*

   Medium-spin states of the neutron-rich nucleus ${}^{87}$Br

   B. M. Nyakó🇭🇺 · J. Timár🇭🇺 · M. Csatlós🇭🇺 · Zs. Dombrádi🇭🇺 · A. Krasznahorkay🇭🇺 · I. Kuti🇭🇺 · D. Sohler🇭🇺 · T. G. Tornyi🇭🇺 · M. Czerwiński🇵🇱 · T. Rza̧ca-Urban🇵🇱 · W. Urban🇵🇱 · P. Ba̧czyk🇵🇱 and 11 other authors

   Medium-spin excited states of the neutron-rich nucleus ${}^{87}$Br were observed and studied for the first time. They were populated in fission of ${}^{235}$U induced by the cold-neutron beam of the PF1B facility of the Institut Laue-Langevin, Grenoble. The measurement of $\gamma$ radiation following fission has been performed using the EXILL array of Ge detectors. The observed level scheme was compared with results of large valence space shell model calculations. The medium-spin level scheme consists of three band-like structures, which can be understood as bands built on the $\pi f_{5/2}$, $\pi (p_{3/2}+f_{5/2})$ and $\pi g_{9/2}$ configurations. The behavior of the observed $\pi g_{9/2}$ band at high spins shows a considerable deviation from the shell model predictions. This deviation in this band is probably the result of an increased collectivity, which can be understood assuming that the $\pi g_{9/2}$ high-$j$ proton polarizes the core.

   nucl-exPRC(2021)·9 citations
4. 04*

   Experimental study of intruder components in light neutron-rich nuclei via single-nucleon transfer reaction

   Wei Liu🇨🇳 · Jian-Ling Lou🇨🇳 · Yan-Lin Ye🇨🇳 · Dan-Yang Pang🇨🇳

   With the development of radioactive beam facilities, studies concerning the shell evolution of unstable nuclei have recently gained prominence. Intruder components, particularly s-wave intrusion, in the low-lying states of light neutron-rich nuclei near N=8 are of importance in the study of shell evolution. The use of single-nucleon transfer reactions in inverse kinematics has been a sensitive tool that can be used to quantitatively investigate the single-particle orbital component of selectively populated states. The spin-parity, spectroscopic factor (or single-particle strength), and effective single-particle energy can all be extracted from such reactions. These observables are often useful to explain the nature of shell evolution, and to constrain, check, and test the parameters used in nuclear structure models. In this article, the experimental studies of the intruder components in low-lying states of neutron-rich nuclei of He, Li, Be, B, and C isotopes using various single-nucleon transfer reactions are reviewed. The focus is laid on the precise determination of the intruder s-wave strength in low-lying states.

   nucl-exnucl-th20 citations
5. 05*

   Pendellösung Interferometry Probes the Neutron Charge Radius, Lattice Dynamics, and Fifth Forces

   Benjamin Heacock🇺🇸 · Takuhiro Fujiie🇯🇵 · Robert W. Haun🇺🇸 · Albert Henins🇺🇸 · Katsuya Hirota🇯🇵 · Takuya Hosobata🇯🇵 · Michael G. Huber🇺🇸 · Masaaki Kitaguchi🇯🇵 · Dmitry A. Pushin🇨🇦 · Hirohiko Shimizu🇯🇵 · Masahiro Takeda🇯🇵 · Robert Valdillez🇺🇸 · Yutaka Yamagata🇯🇵 · Albert Young🇺🇸

   Structure factors describe how incident radiation is scattered from materials such as silicon and germanium and characterize the physical interaction between the material and scattered particles. We use neutron pendellösung interferometry to make precision measurements of the (220) and (400) neutron-silicon structure factors, and achieve a factor of four improvement in the (111) structure factor uncertainty. These data provide measurements of the silicon Debye-Waller factor at room temperature and the mean square neutron charge radius $⟨r_n^2⟩=-0.1101\pm 0.0089{\mathrm{fm}}^2$. Combined with existing measurements of the Debye-Waller factor and charge radius, the measured structure factors also improve constraints on the strength of a Yukawa-modification to gravity by an order of magnitude over the 20 pm to 10 nm length scale range.

   nucl-exScience(2021)·36 citations
6. 06*

   Are the CKM anomalies induced by vector-like quarks? Limits from flavor changing and Standard Model precision tests

   Benedetta Belfatto🇮🇹 · Zurab Berezhiani🇮🇹

   Recent high precision determinations of $V_{us}$ and $V_{ud}$ indicate towards anomalies in the first row of the CKM matrix. Namely, determination of $V_{ud}$ from superallowed beta decays and of $V_{us}$ from kaon decays imply a violation of first row unitarity at about $4\sigma$ level. Moreover, there is tension between determinations of $V_{us}$ obtained from leptonic $K\mu 2$ and semileptonic $K\ell 3$ kaon decays. These discrepancies can be explained if there exist extra vector-like quarks at the TeV scale, which have large enough mixings with the lighter quarks. In particular, extra vector-like weak singlets quarks can be thought as a solution to the CKM unitarity problem and an extra vector-like weak doublet can in principle resolve all tensions. The implications of this kind of mixings are examined against the flavour changing phenomena and SM precision tests. We consider separately the effects of an extra down-type isosinglet, up-type isosinglet and an isodoublet containing extra quarks of both up and down type, and determine available parameter spaces for each case. We find that the experimental constraints on flavor changing phenomena become more stringent with larger masses, so that the extra species should have masses no more than few TeV. Moreover, only one type of extra multiplet cannot entirely explain all the discrepancies, and some their combination is required. We show that these scenarios are testable with future experiments. Namely, if extra vector-like quarks are responsible for CKM anomalies, then at least one of them should be found at scale of few TeV, and anomalous weak isospin violating $Z$-boson couplings with light quarks should be detected if the experimental precision on $Z$ hadronic decay rate is improved by a factor of $2$ or so.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2021)·77 citations
7. 07*

   Charming Charm, Beautiful Bottom, and Quark-Gluon Plasma in the Large Hadron Collider Era

   Santosh K. Das🇮🇳 · Raghunath Sahoo🇮🇳

   After a few microseconds of the creation of our Universe through the Big Bang, the primordial matter was believed to be a soup of the fundamental constituents of matter -- quarks and gluons. This is expected to be created in the laboratory by colliding heavy nuclei at ultra-relativistic speeds. A plasma of quarks and gluons, called Quark-Gluon Plasma (QGP) can be created at the energy and luminosity frontiers in the Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory, New York, USA, and the Large Hadron Collider (LHC) at CERN, Geneva, Switzerland. Heavy quarks, namely the charm and bottom quarks, are considered as novel probes to characterize QGP, and hence the produced Quantum Chromodynamics (QCD) matter. Heavy quark transport coefficients play a significant role in understanding the properties of QGP. Experimental measurements of nuclear suppression factor and elliptic flow can constrain the heavy quark transport coefficients, which are key ingredients for phenomenological studies, and they help to disentangle different energy loss mechanisms. We give a general perspective of the heavy quark drag and diffusion coefficients in QGP and discuss their potentials as probes to disentangle different hadronization mechanisms, as well as to probe the initial electromagnetic fields produced in non-central heavy-ion collisions. Experimental perspectives on future measurements are discussed with special emphasis on heavy-flavors as next-generation probes in view of new technological developments.

   ↳ hep-phhep-exnucl-exnucl-thCurr.Sci.(2021)·3 citations
8. 08*

   Longitudinal double-spin asymmetry for inclusive jet and dijet production in polarized proton collisions at $\sqrt{s}=200$ GeV

   STAR Collaboration: M. S. Abdallah · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · A. Aparin and 378 other authors

   We report high-precision measurements of the longitudinal double-spin asymmetry, $A_{LL}$, for midrapidity inclusive jet and dijet production in polarized $pp$ collisions at a center-of-mass energy of $\sqrt{s}=200\mathrm{GeV}$. The new inclusive jet data are sensitive to the gluon helicity distribution, $\Delta g(x,Q^2)$, for gluon momentum fractions in the range from $x\simeq 0.05$ to $x\simeq 0.5$, while the new dijet data provide further constraints on the $x$ dependence of $\Delta g(x,Q^2)$. The results are in good agreement with previous measurements at $\sqrt{s}=200\mathrm{GeV}$ and with recent theoretical evaluations of prior world data. Our new results have better precision and thus strengthen the evidence that $\Delta g(x,Q^2)$ is positive for $x>0.05$.

   ↳ hep-exnucl-exPRD(2021)·46 citations
9. 09*

   Determine the neutron skin type by relativistic isobaric collisions

   Hao-jie Xu🇨🇳 · Hanlin Li🇨🇳 · Xiaobao Wang🇨🇳 · Caiwan Shen🇨🇳 · Fuqiang Wang🇺🇸

   The effects of neutron skin on the multiplicity ($N_{\mathrm{ch}}$) and eccentricity(${ϵ}_2$) in relativistic ${}_{44}^{96}$Ru+${}_{44}^{96}$Ru and ${}_{40}^{96}$Zr+${}_{40}^{96}$Zr collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV are investigated with the Trento model. It is found that the Ru+Ru/Zr+Zr ratios of the $N_{\mathrm{ch}}$ distributions and ${ϵ}_2$ in mid-central collisions are exquisitely sensitive to the neutron skin type (skin vs.~halo). The state-of-the-art calculations by energy density functional theory (DFT) favor the halo-type neutron skin and can soon be confronted by experimental data. It is demonstrated that the halo-type density can serve as a good surrogate for the DFT density, and thus can be efficiently employed to probe nuclear deformities by using elliptic flow data in central collisions. We provide hereby a proof-of-principle venue to simultaneously determine the neutron skin type, thickness, and nuclear deformity.

   ↳ nucl-thnucl-exPLB(2021)·92 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.