We analyze the sensitivity of fixed-target experiments to sub-GeV thermal relic dark matter models, accounting for variations in both mediator and dark matter mass, and including dark matter production through both on- and off-shell mediators. It is commonly thought that the sensitivity of such experiments is predicated on the existence of an on-shell mediator that is produced and then decays to dark matter. While accelerators do provide a unique opportunity to probe the mediator directly, our analysis demonstrates that their sensitivity extends beyond this commonly discussed regime. In particular, we provide sensitivity calculations that extend into both the effective field theory regime where the mediator is much heavier than the dark matter and the regime of an off-shell mediator lighter than a dark matter particle-antiparticle pair. Our calculations also elucidate the resonance regime, making it clear that all but a fine-tuned region of thermal freeze-out parameter space for a range of simple models is well covered.
Threshold enhancements predicted by the Resonance-Spectrum-Expansion (RSE) production amplitude and observed by the BaBaR Collaboration in open-bottom production above the $B\bar{B}$ threshold, as well as by several collaborations in open-charm production above the $D\bar{D}$ threshold, can also be seen in diphoton amplitudes at energies above 100 GeV. One such threshold effect is visible in tau-tau and muon-muon data of the L3 Collaboration at LEP, and in the diphoton and four-lepton data of the ATLAS and CMS Collaborations at LHC, as it is enhanced by the nearby presence of the Higgs resonan…
Search potential for direct slepton pair production at the CEPC with $\sqrt{s}$ = 360 GeV
University of the Chinese Academy of Sciences（中国科学院大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；Institute of Physics, Henan Academy of Sciences（河南省科学院物理研究所）；Department of Basic Courses, Naval University of Engineering（海军工程大学基础部）
Precise measurements of electroweak processes at the International Linear Collider (ILC) will provide unique opportunities to explore new physics beyond the Standard Model. Fermion pair productions are sensitive to a new contact interaction or a new heavy gauge boson by comparing cross section and angular distribution with expectations of the new physics models. In this proceedings we report a simulation study of fermion pair productions at a center-of-mass energy of 250 GeV, with a focus on lepton pairs, to demonstrate the potential of the first phase of the ILC.
Gluon shadowing effects on J/psi and Upsilon production in p+Pb collisions at sqrt s_NN = 115 GeV and Pb+p collisions at sqrt s_NN = 72 GeV at AFTER@LHC
We report the direct virtual photon invariant yields in the transverse momentum ranges $1\!<\!p_{T}\!<\!3$ GeV/$c$ and $5\!<\!p_T\!<\!10$ GeV/$c$ at mid-rapidity derived from the dielectron invariant mass continuum region $0.10<M_{ee}<0.28$ GeV/$c^{2}$ for 0-80\% minimum-bias Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. A clear excess in the invariant yield compared to the number-of-binary-collisions ($N_{bin}$) scaled $p+p$ reference is observed in the $p_T$ range $1\!<\!p_{T}\!<\!3$ GeV/$c$. For $p_T\!>6$ GeV/$c$ the production follows $N_{bin}$ scaling. Model calculations with contributions…
Statistical Coalescence Model Analysis of J/psi Production in Pb+Pb Collisions at 158 A GeV
在统计合并模型中考虑了重离子碰撞中J/π介子的产生。该模型与NA 50协作组在158 A GeV的Pb+Pb碰撞的实验数据在一个很宽的中心度范围内，包括所谓的“双”抑制域是一致的。J/psi数据的模型描述需要，但是，强大的增强中心Pb+Pb碰撞的开放魅力生产。该模型预测可以在未来的SPS运行中进行检查。
In this paper we discuss the impact of the Double Parton Scattering (DPS) mechanism for the production of $J/ψ$ pairs at the COMPASS energy. We find that the kinematics suppresses the DPS cross section by a factor of $\sim1/2$. The upper limit for the double $J/ψ$ production DPS cross section at the COMPASS energy is estimated. The Feynman-$x$ distributions of double $J/ψ$ production with the CERN $π^-$ beam are presented.
The production of dibaryons, light nuclei and hypertriton in the most central Au+Au collisions at $\sqrt{s_{NN}}=$ 11.5 and 200 GeV are investigated by using a naive coalescence model. The production of light nuclei is studied and found that the production rate reduces by a factor of 330 (1200) for each extra nucleon added to nuclei at $\sqrt{s_{NN}}=$ 11.5 (200) GeV. The $p_{T}$ integrated yield of multistrange hadrons falls exponentially as strangeness quantum number increases. We further investigate strangeness population factor $S_{3}, S_{2}$ as a function of transverse momentum as well as…
