Mon·Dec 30, 2019Monday·December 30, 2019

1. 01*

   Exclusive Hard Processes for Studying Hadron Structures at J-PARC

   Wen-Chen Chang🇹🇼

   With an appropriate hard scale, exclusive hadronic processes could provide novel information of the internal quark-gluon configurations of hadrons. The availability of 10-20 GeV secondary meson beam in the coming high-momentum beam line of Hadron Hall at J-PARC offers an unique opportunity to carry out the measurements of the exclusive hard processes. We address this interesting approach by two possibilities: (a) ${\pi }^{-}p\to K^0\Lambda (1405)$ for the constituent quark structure of $\Lambda (1405)$, and (b) exclusive pion-induced Drell-Yan process ${\pi }^{-}p\to {\gamma }^{\ast }n\to l^{+}{l}^{-}n$ for the generalized parton distributions (GPDs) of nucleons. Realization of such measurements at J-PARC will open up a new way of accessing the internal quark structure of exotic hadrons and also the nucleon GPDs based on a solid theoretical foundation of perturbative QCD.

   nucl-exhep-phnucl-thJPS Conf.Proc.(2021)·0 citations
2. 02*

   Evidence for top quark production in nucleus-nucleus collisions

   Georgios Konstantinos Krintiras (on behalf of the CMS Collaboration)🇺🇸

   Droplets of quark-gluon plasma (QGP), an exotic state of strongly interacting quantum chromodynamics (QCD) matter, are routinely produced in heavy nuclei high-energy collisions. Although the experimental signatures marked a paradigm shift away from expectations of a weakly coupled QGP, a challenge remains as to how the locally deconfined state with a lifetime of a few fm can be resolved. The only colored particle that decays mostly within the QGP is the top quark. Here we demonstrate, for the first time, that top quark decay products are identified, irrespective of whether interacting with the medium (bottom quarks) or not (leptonically decaying W bosons). Using $1.7\pm 0.1\mathrm{n}{\mathrm{b}}^{-1}$ of lead-lead ($A=208$) collision data recorded by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.02 TeV, we report evidence of top quark pair ($\mathrm{t}\bar{\mathrm{t}}$) production. Dilepton final states are selected, and the cross section (${\sigma }_{\mathrm{t}\bar{\mathrm{t}}}$) is measured from a likelihood fit to a multivariate discriminator using lepton kinematic variables. The ${\sigma }_{\mathrm{t}\bar{\mathrm{t}}}$ measurement is additionally performed considering the jets originating from the hadronization of bottom quarks, which improve the sensitivity to the $\mathrm{t}\bar{\mathrm{t}}$ signal process. After background subtraction and analysis corrections, the measured ${\sigma }_{\mathrm{t}\bar{\mathrm{t}}}$ is $2.02\pm 0.69(\mathrm{tot})$ and $2.56\pm 0.82(\mathrm{tot})\mu \mathrm{b}$ in the two cases, respectively, consistent with predictions from perturbative QCD.

   nucl-exNPA(2021)·0 citations
3. 03*

   Evidence of Odderon-exchange from scaling properties of elastic scattering at TeV energies

   T. Csorgo🇭🇺 · T. Novak🇭🇺 · R. Pasechnik🇸🇪 · A. Ster🇭🇺 · I. Szanyi🇭🇺

   We study the scaling properties of the differential cross section of elastic proton-proton ($pp$) and proton-antiproton ($p\bar{p}$) collisions at high energies. We introduce a new scaling function, that scales -- within the experimental errors -- all the ISR data on elastic $pp$ scattering from $\sqrt{s}=23.5$ to $62.5$ GeV to the same universal curve. We explore the scaling properties of the differential cross-sections of the elastic $pp$ and $p\bar{p}$ collisions in a limited TeV energy range. Rescaling the TOTEM $pp$ data from $\sqrt{s}=7$ TeV to $2.76$ and $1.96$ TeV, and comparing it to D0 $p\bar{p}$ data at $1.96$ TeV, our results provide an evidence for a $t$-channel Odderon exchange at TeV energies, with a significance of at least 6.26$\sigma$. We complete this work with a model-dependent evaluation of the domain of validity of the new scaling and its violations. We find that the $H(x)$ scaling is valid, model dependently, within $200$ GeV $\le \sqrt{s}\le$ $8$ TeV, with a $-t$ range gradually narrowing with decreasing colliding energies.

   ↳ hep-phhep-exhep-thnucl-exEPJC(2021)·64 citations
4. 04*

   Theoretical investigation of the antimagnetic rotation in ${}^{104}$Pd

   Zhen-Hua Zhang

   The particle-number-conserving method based on the cranked shell model is used to investigate the antimagnetic rotation band in ${}^{104}$Pd. The experimental moments of inertia and reduced $B(E2)$ transition probabilities are reproduced well. The $J^{(2)}/B(E2)$ ratios are also discussed. The occupation probability of each orbital close to the Fermi surface and the contribution of each major shell to the total angular momentum alignment with rotational frequency are analyzed. The backbending mechanism of the ground state band in ${}^{104}$Pd is understood clearly and the configuration of the antimagnetic rotation after backbending is clarified. In addition, the crossing of a four quasiparticle states with this antimagnetic rotation band is also predicted. By examining the the closing of the four proton hole angular momenta towards the neutron angular momenta, the "two-shears-like" mechanism for this antimagnetic rotation is investigated and two stages of antimagnetic rotation in ${}^{104}$Pd are seen clearly.

   ↳ nucl-thnucl-exCPC(2019)·9 citations
5. 05*

   Configuration and bandhead spin assignments for the 2-quasiparticle rotational bands in the neutron-rich nuclei ${}^{154,156}$Pm

   Shuo-Yi Liu · Miao Huang🇨🇳 · Zhen-Hua Zhang🇨🇳

   The rotational bands in the neutron-rich nuclei ${}^{153-157}$Pm are investigated by a particle-number conserving method. The kinematic moments of inertia for the 1-quasiparticle bands in odd-$A$ Pm isotopes ${}^{153,155,157}$Pm are reproduced quite well by the present calculation. By comparison between the experimental and calculated moments of inertia for the three 2-quasiparticle bands in the odd-odd nuclei ${}^{154,156}$Pm, their configurations and bandhead spins have been assigned properly. For the 2-quasiparticle band in ${}^{154}$Pm, the configuration is assigned as $\pi 5/2^{-}[532]\otimes \nu 3/2^{-}[521]$ ($K^{\pi }=4^{+}$) with the bandhead spin $I_0=4\hslash$. In ${}^{156}$Pm, the same configuration and bandhead spin assignments have been made for the 2-quasiparticle band with lower excitation energy. The configuration $\pi 5/2^{+}[413]\otimes \nu 5/2^{+}[642]$ ($K^{\pi }=5^{+}$) with the bandhead spin $I_0=5\hslash$ is assigned for that with higher excitation energy.

   ↳ nucl-thnucl-exPRC(2019)·5 citations
6. 06*

   Passive Gating Grid for Ion Back Flow Suppression in High Luminosity Collider Experiments

   K. Dehmelt🇺🇸 · P. Garg🇺🇸 · T. K. Hemmick🇺🇸 · A. Milov🇮🇱 · E. Shulga🇮🇱 · V. Zakharov🇷🇺

   Time Projection Chamber (TPC) is one of the main tracking systems for many current and future collider experiments at RHIC and LHC. It has a capability to measure the space points of charged tracks for good momentum resolution as well as the energy loss (dE/dx) for particle identification with good energy resolution. Both of these features depend strongly on the amount of space charge in the TPC gas volume, mainly due to the ions from the amplification stage. An active gating grid has been used thus far to gate the electrons and ions by switching the polarities of the grid wires. Therefore, active gating does introduce a limitation for data taking rates in high luminosity collisions. In this work we propose several options of a passive gating, where a significant reduction of Ion Back Flow (IBF) is possible in a high luminosity environment without any dead time issues due to gating operation. Particularly, the application of a TPC passive gating for the sPHENIX experiment at RHIC is presented, which is currently under development.

   ↳ physics.ins-detnucl-ex0 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.