Wed·Mar 11, 2020Wednesday·March 11, 2020

1. 01*

   Longitudinal eccentricity decorrelations in heavy ion collisions

   Arabinda Behera🇺🇸 · Maowu Nie🇨🇳 · Jiangyong Jia🇺🇸

   In heavy-ion collisions, the harmonic flow $V_n$ of final-state particles are driven by the eccentricity vector ${\mathcal{E}}_n$ that describe the shape of the initial fireball projected in the transverse plane. It is realized recently that the structure and shape of the fireball, and consequently the ${\mathcal{E}}_n$, fluctuate in pseudorapidity $\eta$ in a single event, ${\mathcal{E}}_n(\eta )$. This leads to eccentricity decorrelation between different $\eta$, driving the longitudinal flow decorrelations observed in the experiments. Using a Glauber model with a paramerterized longitudinal structure, we have estimated the eccentricity decorrelations and related them to the measured flow decorrelation coefficients for elliptic flow $n=2$ and triangular flow $n=3$. We investigated the dependence of eccentricity decorrelations on the choice of collision system in terms of the size, asymmetry and deformation of the nuclei. We found that these nuclear geometry effects lead to significant and characteristic patterns on the eccentricity decorrelations, which describe the measured ratios of the flow decorrelations between Xe+Xe and Pb+Pb collisions. These patterns can be searched for using existing experimental data at RHIC and the LHC, and if confirmed, they will provide a mean to improve our understanding of the initial state of the heavy-ion collisions.

   ↳ nucl-thhep-phnucl-exPRResearch(2020)·16 citations
2. 02*

   Semileptonic decays of $D_{(s)}$ mesons

   Zhao-Qian Yao🇨🇳 · Daniele Binosi🇮🇹 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳 · Shu-Sheng Xu🇨🇳 · Hong-Shi Zong🇨🇳

   A symmetry-preserving continuum approach to meson bound-states in quantum field theory, employed elsewhere to describe numerous $\pi$- and $K$-meson electroweak processes, is used to analyse leptonic and semileptonic decays of $D_{(s)}$ mesons. Each semileptonic transition is conventionally characterised by the value of the dominant form factor at $t=0$ and the following results are obtained herein: $f_{+}^{D_s\to K}(0)=0.673(40)$; $f_{+}^{D\to \pi }(0)=0.618(31)$; and $f_{+}^{D\to K}(0)=0.756(36)$. Working with the computed $t$-dependence of these form factors and standard averaged values for $|V_{cd}|$, $|V_{cs}|$, one arrives at the following predictions for the associated branching fractions: ${\mathcal{B}}_{D_s^{+}\to K^0{e}^{+}{\nu }_e}=3.31(33)\times 10^{-3}$; ${\mathcal{B}}_{D^0\to {\pi }^{-}{e}^{+}{\nu }_e}=2.73(22)\times 10^{-3}$; and ${\mathcal{B}}_{D^0\to K^{-}{e}^{+}{\nu }_e}=3.83(28)$%. Alternatively, using the calculated $t$-dependence, agreement with contemporary empirical results for these branching fractions requires $|V_{cd}|=0.221(9)$, $|V_{us}|=0.953(34)$. With all $D_{(s)}$ transition form factors in hand, the nature of SU$(3)$-flavour symmetry-breaking in this array of processes can be analysed; and just as in the $\pi$-$K$ sector, the magnitude of such effects is found to be determined by the scales associated with emergent mass generation in the Standard Model, not those originating with the Higgs mechanism.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2020)·18 citations
3. 03*

   Few-body structures in the mirror nuclei, ${}^{11}$O and ${}^{11}$Li

   E. Garrido🇪🇸 · A.S. Jensen🇩🇰

   We investigate the dripline mirror nuclei, ${}^{11}$Li and ${}^{11}$O, located on the neutron and proton dripline, respectively. We calculate the lowest four states, $3/2^{-}$, $1/2^{+}$, $3/2^{+}$ and $5/2^{+}$, built on double occupancy in the nuclear $s_{1/2}$ and $p_{1/2}$ valence single-particle states. We use the hyperspherical adiabatic expansion method to solve the three-body problem for a frozen nuclear core surrounded by two identical nucleons. The four analogue states in ${}^{11}$O are obtained with precisely the same interactions as used for the four states in ${}^{11}$Li, except for addition of the Coulomb interaction from the charge of the substituted valence protons. Surprisingly the four energies deviate from each other only by less than a few hundred keV. Any of them could then turn out to be the ground state, due to the uncertainty related to the angular momentum and parity dependence of the three-body potential. Still, our calculations marginally favor the $1/2^{+}$ state. The structures of these four states in ${}^{11}$O deviate substantially from the analogue states in the mirror, ${}^{11}$Li.

   ↳ nucl-thnucl-exPRC(2020)·10 citations
4. 04*

   On survey of nuclei and hypernuclei in multifragmentation

   N. Buyukcizmeci🇹🇷 · R. Ogul🇹🇷 · A.S. Botvina🇩🇪 · M. Bleicher🇩🇪

   Multifragmentation reactions are dominating processes for the decomposition of highly excited nuclei leading to the fragment production in heavy-ion collisions. At high energy reactions strange particles are abundantly produced. We present a novel development of the Statistical multifragmentation model (SMM) as its generalization for the hyper-matter which is formed after the hyperon capture. In this way, it is possible to describe its disintegration into normal and hyper-nuclei. Some properties of hyper-nuclei and their binding energies can be determined from the comparison of the isotope yields. The main focus of this method is to investigate strange and multi-strange hypernuclei since their properties are not easy to measure in traditional hyper-nuclei experiments.

   ↳ nucl-thhep-exnucl-exPhys.Scripta(2020)·0 citations
5. 05*

   Extracting the Transverse Momentum Dependent Polarizing Fragmentation Functions

   Daniel Callos🇺🇸 · Zhong-Bo Kang🇺🇸 · John Terry🇺🇸

   We demonstrate that spontaneous transverse polarization of Lambda baryon ($\Lambda$) production in $e^{+}{e}^{-}$ annihilation can be described using the transverse momentum dependent polarizing fragmentation functions (TMD PFFs). Using a simple Gaussian model, we perform an extraction of the TMD PFFs by fitting the BELLE collaboration's recent measurement of the $\Lambda$ transverse polarization in back-to-back $\Lambda +h$ production in $e^{+}{e}^{-}$ collisions, $e^{-}+e^{+}\to {\Lambda }^{\uparrow }+h+X$. We find that this simple model accurately describes the experimental data for $\Lambda$ production associated with pions and kaons, and we are able to determine TMD PFFs for different quark flavors. We use these newly extracted TMD PFFs to make predictions for the transverse polarization of $\Lambda$ produced in semi-inclusive deep inelastic scattering at a future electron-ion collider, and find that such a polarization is around $10\%$ and should be measurable.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2020)·69 citations
6. 06*

   Covariant model for the Dalitz decay of the $N(1535)$ resonance

   G. Ramalho🇧🇷 · M.T. Peña🇵🇹

   We develop a covariant model for the ${\gamma }^{\ast }N\to N(1535)$ transition in the timelike kinematical region, the region where the square momentum transfer $q^2$ is positive. Our starting point is the covariant spectator quark model constrained by data in the spacelike kinematical region ($Q^2=-q^2>0$). The model is used to estimate the contributions of valence quarks to the transition form factors, and one obtains a fair description of the Dirac form factor at intermediate and large $Q^2$. For the Pauli form factor there is evidence that beyond the quark-core contributions there are also significant contributions of meson cloud effects. Combining the quark-core model with an effective description of the meson cloud effects, we derive a parametrization of the spacelike data that can be extended covariantly to the timelike region. This extension enabled us to estimate the Dalitz decay widths of the $N(1535)$ resonance, among other observables. Our calculations can help in the interpretation of the present experiments at HADES ($pp$ collisions and others).

   ↳ hep-phhep-exnucl-exnucl-thPRD(2020)·27 citations
7. 07*

   Hadronic vacuum polarization: $(g-2{)}_{\mu }$ versus global electroweak fits

   Andreas Crivellin🇨🇭 · Martin Hoferichter🇨🇭 · Claudio Andrea Manzari🇨🇭 · Marc Montull🇨🇭

   Hadronic vacuum polarization (HVP) is not only a critical part of the Standard Model (SM) prediction for the anomalous magnetic moment of the muon $(g-2{)}_{\mu }$, but also a crucial ingredient for global fits to electroweak (EW) precision observables due to its contribution to the running of the fine-structure constant encoded in $\Delta {\alpha }_{\text{had}}^{(5)}$. We find that with modern EW precision data, including the measurement of the Higgs mass, the global fit alone provides a competitive, independent determination of $\Delta {\alpha }_{\text{had}}^{(5)}{|}_{\text{EW}}=270.2(3.0)\times 10^{-4}$. This value actually lies below the range derived from $e^{+}{e}^{-}\to \text{hadrons}$ cross-section data, and thus goes into the opposite direction as would be required if a change in HVP were to bring the SM prediction for $(g-2{)}_{\mu }$ into agreement with the Brookhaven measurement. Depending on the energy where the bulk of the changes in the cross section occurs, reconciling experiment and SM prediction for $(g-2{)}_{\mu }$ by adjusting HVP would thus not necessarily weaken the case for physics beyond the SM (BSM), but to some extent shift it from $(g-2{)}_{\mu }$ to the EW fit. We briefly explore some options of BSM scenarios that could conceivably explain the ensuing tension.

   ↳ hep-phhep-exhep-latnucl-ex+1PRL(2020)·266 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.