Thu·May 28, 2020Thursday·May 28, 2020

1. 01*

   Measurement of the ${}^{229}$Th isomer energy with a magnetic micro-calorimeter

   Tomas Sikorsky · Jeschua Geist · Daniel Hengstler · Sebastian Kempf · Loredana Gastaldo🇩🇪 · Christian Enss🇩🇪 · Christoph Mokry · Jörg Runke · Christoph E. Düllmann🇩🇪 · Peter Wobrauschek · Kjeld Beeks🇦🇹 · Veronika Rosecker and 4 other authors

   We present a measurement of the low-energy (0--60keV) $\gamma$ ray spectrum produced in the $\alpha$-decay of ${}^{233}$U using a dedicated cryogenic magnetic micro-calorimeter. The energy resolution of $\sim$$10$eV, together with exceptional gain linearity, allow us to measure the energy of the low-lying isomeric state in ${}^{229}$Th using four complementary evaluation schemes. The most accurate scheme determines the ${}^{229}$Th isomer energy to be $8.10(17)$eV, corresponding to 153.1(37)nm, superseding in precision previous values based on $\gamma$ spectroscopy, and agreeing with a recent measurement based on internal conversion electrons. We also measure branching ratios of the relevant excited states to be $b_{29}=9.3(6)\%$ and $b_{42}=0.3(3)\%$.

   nucl-exnucl-thphysics.ins-detPRL(2020)·96 citations
2. 02*

   Overview of fluctuation and correlation measurements

   Anar Rustamov🇦🇿

   One of the ultimate goals of nuclear collision experiments at high energy is to map the phase diagram of strongly interacting matter. A very challenging task is the determination of the QCD phase structure including the search for critical behavior and verification of the possible existence of a critical end point of a first order phase transition line. A promising tool to probe the presence of critical behavior is the study of fluctuations and correlations of conserved charges since, in a thermal system, these fluctuations are directly related to the equation of state (EoS) of the system under the study. In this report an overview is given of several experimental measurements on net-proton multiplicity distributions such as cumulants and multi-particle correlation functions.

   nucl-exNPA(2021)·8 citations
3. 03*

   Low Gain Avalanche Detectors for the HADES reaction time (T${}_0$) detector upgrade

   J. Pietraszko🇩🇪 · T. Galatyuk🇩🇪 · V. Kedych🇩🇪 · M. Kis🇩🇪 · W. Koenig🇩🇪 · M. Koziel🇩🇪 · W. Krüger🇩🇪 · R. Lalik🇵🇱 · S. Linev🇩🇪 · J. Michel🇩🇪 · S. Moneta🇮🇹 · A. Rost🇩🇪 and 6 other authors

   Low Gain Avalanche Detector (LGAD) technology has been used to design and construct prototypes of time-zero detector for experiments utilizing proton and pion beams with High Acceptance Di-Electron Spectrometer (HADES) at GSI Darmstadt, Germany. LGAD properties have been studied with proton beams at the COoler SYnchrotron (COSY) facility in Jülich, Germany. We have demonstrated that systems based on a prototype LGAD operated at room temperature and equipped with leading-edge discriminators reach a time precision below 50 ps. The application in the HADES, experimental conditions, as well as the test results obtained with proton beams are presented.

   ↳ physics.ins-detnucl-exEPJA(2020)·20 citations
4. 04*

   $J/\psi$ meson production in association with an open charm hadron at the LHC: A reappraisal

   Hua-Sheng Shao🇫🇷

   We critically (re)examine the associated production process of a $J/\psi$ meson plus an open charm hadron at the LHC in the proton-proton ($pp$) and proton-lead ($p\mathrm{Pb}$) collisions. Such a process is very intriguing in the sense of tailoring to explore the double parton structure of nucleons and to determine the geometry of partons in nuclei. In order to interpret the existing $pp$ data with the LHCb detector at the center-of-mass energy $\sqrt{s}=7$ TeV, we introduce two overlooked mechanisms for the double parton scattering (DPS) and single parton scattering (SPS) processes. Besides the conventional DPS mode, where the two mesons are produced almost independently in the two separate scattering subprocesses, we propose a novel DPS mechanism that the two constituent (heavy) quarks stemming from two hard scatterings can form into a composite particle, like the $J/\psi$ meson, during the hadronization phase. However, it turns out the corresponding contribution is small in $J/\psi +c\bar{c}$ hadroproduction. On the contrary, we point out that the resummation of the initial state logarithms due to gluon splitting into a charm quark pair is crucial to understand the LHCb measurement, which was overlooked in the literature. We perform a proper matching between the perturbative calculations in different initial-quark flavor number schemes, generically referring to the variable flavor number scheme. The new variable flavor number scheme calculation for the process strongly enhance the SPS cross sections, almost closing the discrepancies between theory and experiment. Finally, we present our predictions for the forthcoming LHCb measurement in $p\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=8.16$ TeV. Some interesting observables are exploited to set up the control regions of the DPS signal and to probe the impact-parameter dependent parton densities in lead.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2020)·18 citations
5. 05*

   The Constituent Counting Rule and Omega Photoproduction

   Trevor Reed🇺🇸 · Christopher Leon🇺🇸 · Frank Vera🇺🇸 · Lei Guo🇺🇸 · Brian Raue🇺🇸

   The constituent counting ruling (CCR) has been found to hold for numerous hard, exclusive processes. It predicts the differential cross section at high energies and fixed $\cos {\theta }_{c.m.}$ should follow $\frac{d\sigma }{dt}\sim \frac{1}{s^{n-2}}$, where $n$ is the minimal number of constituents involved in the reaction. Here we provide an in-depth analysis of the reaction $\gamma p\to \omega p$ at ${\theta }_{c.m.}\sim 90^{\circ }$ using CLAS data with an energy range of $s=5-8$ GeV${}^2$, where the CCR has been shown to work in other reactions. We argue for a stringent method to select data to test the CCR and utilize a Taylor-series expansion to take advantage of data from nearby angle bins in our analysis. Naïvely, this reaction would have $n=9$ (or $n=10$ if the photon is in a $q\bar{q}$ state) and we would expect a scaling of $\sim s^{-7}$ ($s^{-8}$). Instead, a scaling of $s^{-(9.08\pm 0.11)}$ was observed. Explanations for this apparent failure of the naïve CCR assumptions are examined.

   ↳ hep-phnucl-exnucl-thPRC(2021)·3 citations
6. 06*

   Neutron skin of ${}^{48}$Ca consistent with experimental data on skins

   Shingo Tagami🇯🇵 · Jun Matsui · Maya Takechi🇩🇪 · Masanobu Yahiro🇯🇵

   [Background]: In our previous paper, we predicted $r_{\mathrm{skin}}$, $r_{\mathrm{p}}$, $r_{\mathrm{n}}$, $r_{\mathrm{m}}$ for ${}^{40-60,62,64}$Ca after determining the neutron dripline, using the Gogny-D1S HFB with and without the angular momentum projection (AMP). We found that effects of the AMP are small. Very lately, Tanaka {\it et al.} measured interaction cross sections ${\sigma }_{\mathrm{I}}$ for ${}^{42-51}$Ca, determined $r_{\mathrm{m}}$ from the ${\sigma }_{\mathrm{I}}$, and deduced skin $r_{\mathrm{skin}}$ and $r_{\mathrm{n}}$ from the $r_{\mathrm{m}}$ and the $r_{\mathrm{p}}(\exp )$ evaluated from the electron scattering. Comparing our results with the data, we find for ${}^{42-48}$Ca that GHFB and GHFB+AMP reproduce the data on $r_{\mathrm{skin}}$, $r_{\mathrm{n}}$, $r_{\mathrm{m}}$, but not for $r_{\mathrm{p}}(\exp )$. [Aim]: Our purpose is to determine a value of $r_{\mathrm{skin}}^{48}$ by using GHFB+AMP and the constrained GHFB (cGHFB) in which the calculated value is fitted to $r_{\mathrm{p}}(\exp )$. [Results]: For ${}^{42,44,46,48}$Ca, cGHFB hardly changes $r_{\mathrm{skin}}$, $r_{\mathrm{m}}$, $r_{\mathrm{n}}$ calculated with GHFB+AMP, except for $r_{\mathrm{skin}}^{48}$. For $r_{\mathrm{skin}}^{48}$, the cGHFB result is $r_{\mathrm{skin}}^{48}=0.190$fm, while $r_{\mathrm{skin}}^{48}=0.159$fm for GHFB+AMP. We should take the upper and the lower bound of GHFB+AMP and cGHFB. The result $r_{\mathrm{skin}}^{48}=0.159-0.190$fm consists with the $r_{\mathrm{skin}}^{48}({\sigma }_{\mathrm{I}})$ and the data $r_{\mathrm{skin}}^{48}($E1$pE)$ obtained from high-resolution $E1$ polarizability experiment ($E1$pE). Using the $r_{\mathrm{skin}}^{48}$-$r_{\mathrm{skin}}^{208}$ relation with strong correlation of Ref.[3], we transform the data $r_{\mathrm{skin}}^{208}$ determined by PREX and $E1$pE to the corresponding values, $r_{\mathrm{skin}}^{48}(\mathrm{tPREX})$ and $r_{\mathrm{skin}}^{48}(\mathrm{t}$E1$pE)$. Our result is consistent also for $r_{\mathrm{skin}}^{48}(\mathrm{tPREX})$ and $r_{\mathrm{skin}}^{48}(\mathrm{t}$E1$pE)$.

   ↳ nucl-thnucl-ex6 citations
7. 07*

   Explaining $b\to s{\ell }^{+}{\ell }^{-}$ and the Cabibbo Angle Anomaly with a Vector Triplet

   Bernat Capdevila🇮🇹 · Andreas Crivellin🇨🇭 · Claudio Andrea Manzari🇨🇭 · Marc Montull🇨🇭

   The most statistically significant hints for new physics in the flavor sector are discrepancies between theory and experiment in $B$ decays to lepton pairs ($b\to s{\ell }^{+}{\ell }^{-}$) and a deficit in $1^{\mathrm{st}}$ row CKM unitarity (the Cabibbo Angle anomaly). We propose that these anomalies can be reconciled by a simplified model with massive gauge bosons transforming in the adjoint representation of $SU(2{)}_L$. After calculating the impact of this model on $B$ decays, observables testing charged current lepton flavor universality (LFU), electro-weak precision observables and LHC searches we perform a global fit to all available data. We find that our model can provide a consistent common explanation of both anomalies and that the fit to the data is more than $7\sigma$ better than the fit of the SM. The model also predicts interesting correlations between LFU violation in the charged current and $b\to s{\ell }^{+}{\ell }^{-}$ data which can be tested experimentally in the near future.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2021)·81 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.