Wed·May 8, 2019Wednesday·May 8, 2019

1. 01*

   Measurement of the production of charm jets tagged with D${}^0$ mesons in pp collisions at $\sqrt{s}$= 7 TeV

   ALICE Collaboration

   The production of charm jets in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=7$ TeV was measured with the ALICE detector at the CERN Large Hadron Collider. The measurement is based on a data sample corresponding to a total integrated luminosity of $6.23$ ${\mathrm{nb}}^{-1}$, collected using a minimum-bias trigger. Charm jets are identified by the presence of a D${}^0$ meson among their constituents. The D${}^0$ mesons are reconstructed from their hadronic decay D${}^0\to$K${}^{-}{\pi }^{+}$. The D${}^0$-meson tagged jets are reconstructed using tracks of charged particles (track-based jets) with the anti-$k_{\mathrm{T}}$ algorithm in the jet transverse momentum range $5<p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}<30$ $GeV/c$ and pseudorapidity $|{\eta }_{\mathrm{jet}}|<0.5$. The fraction of charged jets containing a D${}^0$-meson increases with $p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}$ from $0.042\pm 0.004(\mathrm{stat})\pm 0.006(\mathrm{syst})$ to $0.080\pm 0.009(\mathrm{stat})\pm 0.008(\mathrm{syst})$. The distribution of D${}^0$-meson tagged jets as a function of the jet momentum fraction carried by the D${}^0$ meson in the direction of the jet axis ($z_{||}^{\mathrm{ch}}$) is reported for two ranges of jet transverse momenta, $5<p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}<15$ $GeV/c$ and $15<p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}<30$ $GeV/c$ in the intervals $0.2<z_{||}^{\mathrm{ch}}<1.0$ and $0.4<z_{||}^{\mathrm{ch}}<1.0$, respectively. The data are compared with results from Monte Carlo event generators (PYTHIA 6, PYTHIA 8 and Herwig 7) and with a Next-to-Leading-Order perturbative Quantum Chromodynamics calculation, obtained with the POWHEG method and interfaced with PYTHIA 6 for the generation of the parton shower, fragmentation, hadronisation and underlying event.

   nucl-exhep-exJHEP(2019)·61 citations
2. 02*

   Exploration of jet substructure using iterative declustering in pp and Pb-Pb collisions at LHC energies

   ALICE Collaboration

   The ALICE collaboration at the CERN LHC reports novel measurements of jet substructure in pp collisions at $\sqrt{s}$= 7 TeV and central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV. Jet substructure of track-based jets is explored via iterative declustering and grooming techniques. We present the measurement of the momentum sharing of two-prong substructure exposed via grooming, the $z_{\mathrm{g}}$, and its dependence on the opening angle, in both pp and Pb-Pb collisions. We also present the first measurement of the distribution of the number of branches obtained in the iterative declustering of the jet, which is interpreted as the number of its hard splittings. In Pb-Pb collisions, we observe a suppression of symmetric splittings at large opening angles and an enhancement of splittings at small opening angles relative to pp collisions, with no significant modification of the number of splittings. The results are compared to predictions from various Monte Carlo event generators to test the role of important concepts in the evolution of the jet in the medium such as color coherence.

   nucl-exhep-exPLB(2020)·125 citations
3. 03*

   Measurement of charged jet cross section in pp collisions at $\sqrt{s}=5.02$ TeV

   ALICE Collaboration

   The cross section of jets reconstructed from charged particles is measured in the transverse momentum range of $5<p_{\mathrm{T}}<100\mathrm{GeV}/c$ in pp collisions at the center-of-mass energy of $\sqrt{s}=5.02\mathrm{TeV}$ with the ALICE detector. The jets are reconstructed using the anti-$k_{\mathrm{T}}$ algorithm with resolution parameters $R=0.2$, $0.3$, $0.4$, and $0.6$ in the pseudorapidity range $|\eta |<0.9-R$. The charged jet cross sections are compared with the leading order (LO) and to next-to-leading order (NLO) perturbative Quantum ChromoDynamics (pQCD) calculations. It was found that the NLO calculations agree better with the measurements. The cross section ratios for different resolution parameters were also measured. These ratios increase from low $p_{\mathrm{T}}$ to high $p_{\mathrm{T}}$ and saturate at high $p_{\mathrm{T}}$, indicating that jet collimation is larger at high $p_{\mathrm{T}}$ than at low $p_{\mathrm{T}}$. These results provide a precision test of pQCD predictions and serve as a baseline for the measurement in Pb$-$Pb collisions at the same energy to quantify the effects of the hot and dense medium created in heavy-ion collisions at the LHC.

   nucl-exhep-exPRD(2019)·53 citations
4. 04*

   Systematic study of $\alpha$ decay half-lives based on Gamow--like model with a screened electrostatic barrier

   Jun-Hao Cheng🇨🇳 · Jiu-Long Chen🇨🇳 · Jun-Gang Deng · Xi-Jun Wu · Xiao-Hua Li🇨🇳 · Peng-Cheng Chu🇨🇳

   In the present work we systematically study $\alpha$ decay half-lives of $Z>51$ nuclei using the modified Gamow-like model which includes the effects of the centrifugal potential and electrostatic shielding. For the case of even-even nuclei, this model contains two adjustable parameters: the parameter $a$ related to the screened electrostatic barrier and the radius constant $r_0$, while for the case of odd-odd and odd-A nuclei, it is added a new parameter i.e. hindrance factor $h$ which is used to describe the effect of an odd-proton and/or an odd-neutron. Our calculations can well reproduce the experimental data. In addition, we use this modified Gamow-like model to predict the $\alpha$-decay half-lives of seven even-even nuclei with $Z=120$ and some un-synthesized nuclei on their $\alpha$ decay chains.

   ↳ nucl-thnucl-exNPA(2019)·19 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.