In this paper we propose to use the measurement of the thermal Quark-Gluon Plasma (QGP) dilepton spectra in the Intermediate Mass Region (IMR) of heavy-ion collisions, as a new method to search for GeV-scale dark gauge bosons (gamma' or Z'). Such light mediators are a common feature of light (i.e. low mass) dark matter scenarios, which have been invoked to explain puzzling signals in dark matter indirect and direct detection experiments. First we show that a light gamma' or Z' will generate a resonant enhancement of the dilepton spectrum produced thermally by the QGP, at an energy corresponding to the dark gauge boson mass. Secondly, using data from the PHENIX experiment, we are able to set an upper limit on the combined coupling of this new gauge boson to quarks and leptons (independently of their vectorial or axial nature) chi_q chi_e < 10^(-3) at the 95% confidence level for a gauge boson mass in the range 1.5 - 2.5 GeV. This result complements previous searches for new light gauge bosons and probes a new region of the parameter space, particularly interesting in the case of non-universal couplings to quarks and leptons. Prospects for the discovery of such a boson by the ALICE collaboration are also discussed.
The rate of the emission of the high energy low-mass dileptons from the QGP is found in the first nonvanishing order with respect to strong coupling. We base on the real-time kinetic approach [2] without an explicit assumption about a complete thermal equilibrium in the emitting system. For the class of the partons distributions which may simulate that of the "hot glue scenario"[1] the rate of emission is found analytically . ( Figures can be obtained from the author )
The rate of emission of heavy dileptons from QGP is found without an assumption of its complete thermal equilibrium. We base on the real-time quantum field kinetic approach [1] and use the expansion up to the second order with respect to strong coupling constant $g$. The final answer is not free from the collinear singularities and we show that this is the actual issue. As a result the main contribution to the rate of the heavy dileptons production at $M/T \sim 10$ comes from the process $q\bar{q}g\rightarrow γ^{*}$. ( Figures can be obtained from the author )
We study the \textit{non-ideal} effects arising due to viscosity (both bulk and shear), equation of state ($ε\neq 3P$) and cavitation on thermal dilepton production from QGP at RHIC energies. We calculate the first order corrections to the dilepton production rates due to shear and bulk viscosities. Ignoring the cavitation can lead to a wrong estimation of dilepton spectra. We show that the shear viscosity can enhance the thermal dilepton spectra whereas the bulk viscosity can suppress it. We present the combined effect of bulk and shear viscosities on the dilepton spectra.
We discuss dilepton production from a quark-gluon plasma which has a time-dependent anisotropy in momentum space. A phenomenological model for the hard momentum scale, p_hard(tau) and the plasma anisotropy parameter, xi(tau), is presented. The model interpolates between early-time 1+1 free streaming behavior (tau << tau_iso) and late-time ideal 1+1 hydrodynamical behavior (tau >> tau_iso). Using this model, we find that the dilepton rate arising from electromagnetic annihilations of quarks in the kinematic range 3 <p_T< 8 GeV is sensitive to the assumed isotropization time of the system, tau_i…
We consider the thermal production of dileptons and photons at temperatures above the critical temperature in QCD. We use a model where color excitations are suppressed by a small value of the Polyakov loop, the semi Quark-Gluon Plasma (QGP). Comparing the semi-QGP to the perturbative QGP, we find a mild enhancement of thermal dileptons. In contrast, to leading logarithmic order in weak coupling there are far fewer hard photons from the semi-QGP than the usual QGP. To illustrate the possible effects on photon and dileptons production in heavy ion collisions, we integrate the rate with a realis…
Electromagnetic probes such as direct photons and dileptons are crucial to study the properties of a Quark-Gluon Plasma (QGP) created in heavy ion collisions. Based on the (3+1)-dimensional event-by-event viscous hydrodynamic model EPOS 3.102, we calculated the anisotropic emission of thermal photons and dileptons in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) energy $\sqrt{s_{NN}}=200$~GeV. Thermal emissions from both QGP phase and hadronic gas phase are considered, with AMY rate for photons and Lattice QCD based rates for dileptons in QGP phase. For emission from hadron ga…
We calculate the production of dileptons and photons in the presence of a nontrivial Polyakov loop in QCD. This is applicable to the semi-Quark Gluon Plasma (QGP), at temperatures above but near the critical temperature for deconfinement. The Polyakov loop is small in the semi-QGP, and near unity in the perturbative QGP. Working to leading order in the coupling constant of QCD, we find that there is a mild enhancement, ~ 20%, for dilepton production in the semi-QGP over that in the perturbative QGP. In contrast, we find that photon production is strongly suppressed in the semi-QGP, by about an…
The QGP that might be created in ultrarelativistic heavy-ion collisions is expected to radiate thermal dilepton radiation. However, this thermal dilepton radiation interferes with dileptons originating from hadron decays. In the invariant mass region between the $ϕ$ and $J/Ψ$ peak ($1\,$GeV$\lesssim M_{\ell^+ \ell^-} \lesssim 3 \,$GeV) the most substantial background of hadron decays originates from correlated D$\bar{\mathrm{D}}$-meson decays. We evaluate this background using a Langevin simulation for charm quarks. As background medium we utilize the well-tested UrQMD-hybrid model. The requir…
A fireball of QGP is evoluted at temperature dependent chemical potential by a statistical model in the pionic medium. We study the dilepton emission rate at temperature dependent chemical potential (TDCP) from such a fireball of QGP. In this model, we take the dynamical quark mass as a finite value dependence on temparature and parametrization factor of the QGP evolution. The temperature and factor in quark mass enhance in the growth of the droplets as well as in the dilepton emission rates. The emission rate from the plasma shows dilepton spectrum in the intermediate mass region (IMR) of (1.…
We consider LHC searches for dilepton resonances in an intermediate mass range, $\sim 10 -80$ GeV. We adopt a kinetically mixed $Z'$ as an example of weakly coupled new physics that might have evaded detection at previous experiments but which could still be probed by LHC dilepton spectrum measurements in this mass range. Based on Monte Carlo simulations, we estimate that existing data from the 7 and 8 TeV LHC could be used to test values of the kinetic mixing parameter $ε$ several times smaller than precision electroweak upper bounds, were an appropriate analysis to be carried out by one of t…
Relativistic heavy-ion collisions produce a hot and dense thermalized medium, that is expected to emit thermal radiation in form of dileptons. These dileptons are not affected by the strong force and are therefore a clean probe for the possible creation of a Quark Gluon Plasma (QGP). However, electroweak decays of open-charm mesons are expected to induce a substantial background in the invariant mass region between the $ϕ$ and $J/Ψ$ peak ($1\,\text{GeV} \lesssim M_{\ell^+ \ell^-} \lesssim 3 \,\text{GeV}$) of the thermal QGP radiation. To evaluate this background radiation we apply a Langevin a…
We study the dynamics of open charm production and the dilepton radiation of the semi-leptonic decays of correlated $D\bar D$ pairs versus the quark-gluon plasma (QGP) radiation and hadronic sources in relativistic heavy-ion collisions. Our study is based on the Parton-Hadron-String Dynamics (PHSD) transport approach employing a non-perturbative QCD description of the strongly interacting quark-gluon plasma (sQGP) in terms of dynamical quasiparticles and the EoS based on lattice QCD. We compare the PHSD results for charm observables with the calculations from BAMPS (Boltzmann Approach to Multi…
Dileptons are considered as one of the cleanest signals of the quark-gluon plasma (QGP), however, the QGP radiation is masked by many 'background' sources from either hadronic decays or semileptonic decays from correlated charm pairs. In this study we investigate the relative contribution of these channels in heavy-ion collisions from $\sqrt{s_{\rm NN}}=$ 8 GeV to 5 TeV with a focus on the competition between the thermal QGP radiation and the semileptonic decays from correlated $D-$meson pairs. As a 'tool' we employ the parton-hadron-string dynamics (PHSD) transport approach to study dilepton …
Dilepton production from the quark-gluon plasma (QGP) phase of ultra-relativistic heavy-ion collisions is computed using the leading-order (3+1)-dimensional anisotropic hydrodynamics. It is shown that high-energy dilepton spectrum is sensitive to the initial local-rest-frame momentum-space anisotropy of the QGP. Our findings suggest that it may be possible to constrain the early-time momentum-space anisotropy in relativistic heavy-ion collisions using high-energy dilepton yields.
We obtain the thermal photon and dilepton production rates in a strongly coupled quark-gluon plasma (QGP) at both zero and nonzero baryon chemical potential using a bottom-up Einstein-Maxwell-Dilaton (EMD) holographic model that is in good quantitative agreement with the thermodynamics of $(2+1)$-flavor lattice QCD around the crossover transition for baryon chemical potentials up to 400 MeV, which may be reached in the beam energy scan (BES) at RHIC. We find that increasing the temperature $T$ and the baryon chemical potential $μ_B$ enhances the peak present in both spectra. We also obtain the…
Production rates of dileptons and photons from the quark-gluon (QGP) phase are calculated taking into account effects of confinement and spontaneous chiral symmetry breaking (χSB) not far from the transition temperature $T_c$. We find that the production rates of dileptons with large momenta and of photons originating from the QGP around $T_c$ are suppressed by the χSB effect. We also discuss to what extent information about details of the chiral transition, such as its characteristic temperature range and the steepness of the crossover, are reflected in these quantities.
We investigate the temperature dependence of the thermal dilepton rate and the electrical conductivity of the gluon plasma at temperatures of $1.1T_c$, $1.3T_c$ and $1.5T_c$ in quenched QCD. Making use of non-perturbatively clover-improved Wilson valence quarks allows for a clean extrapolation of the vector meson correlation function to the continuum limit. We found that the vector correlation function divided by $T^3$ is almost temperature independent in the current temperature window. The spectral functions are obtained by $χ^2$ fitting of phenomenologically inspired Ansätze for the spectral…
We discuss the latest theoretical results on direct photon and dilepton production from relativistic heavy-ion collisions. While the dilepton spectra at low invariant mass show in-medium effects like a collisional broadening of the vector meson spectral functions, the dilepton yield at high invariant masses (above 1.1 GeV) is dominated by QGP contributions for central heavy-ion collisions at relativistic energies. The present status of the photon $v_2$ "puzzle" - a large elliptic flow $v_2$ of the direct photons experimentally observed at RHIC and LHC energies - is also addressed. The role of …
The collective behavior of hadrons and of electromagnetic radiation in heavy-ion collisions has been widely used to study the properties of the the Quark-Gluon Plasma (QGP). Indeed this collectivity, as measured by anisotropic flow coefficients, can be used to constrain the transport properties of QGP. The goal of this contribution is to investigate the influence of the specific bulk viscosity ($ζ/s$) on dilepton production, both at Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) energies. We explore the sensitivity of dileptons to dynamical features that bulk viscosity …
We propose a novel relation between the low-mass enhancement of dielectrons observed at PHENIX and transport coefficients of QGP such as the charge diffusion constant $D$ and the relaxation time $τ_{\rm J}$. We parameterize the transport peak in the spectral function using the second-order relativistic dissipative hydrodynamics by Israel and Stewart. Combining the spectral function and the full (3+1)-dimensional hydrodynamical evolution with the lattice EoS, theoretical dielectron spectra and the experimental data are compared. Detailed analysis suggests that the low-mass dilepton enhancement …
In this work the rapidity and transverse momentum dependence of the nuclear modification ratio is evaluated for the dilepton production at RHIC and LHC, using the Color Glass Condensate (CGC) framework. The ratio is compared for two distinct dilepton mass values, concerning the transverse momentum distribution, and a suppression of the Cronin peak is verified even for large mass. The nuclear modification ratio suppression in the dilepton rapidity spectra, as obtained for hadrons at RHIC, is verified for LHC energies at large transverse momentum, although not present at RHIC energies. These res…
We calculate dilepton production rates from a fireball adapted to the kinematical conditions realized in ultrarelativistic heavy ion collisions over a broad range of beam energies. The freeze-out state of the fireball is fixed by hadronic observables. We use this information combined with the initial geometry of the collision region to follow the space-time evolution of the fireball. Assuming entropy conservation, its bulk thermodynamic properties can then be uniquely obtained once the equation of state (EoS) is specified. The high-temperature (QGP) phase is modelled by a non-perturbative quas…
Theories of quantum gravity suggest the existence of a minimal length scale. It is interesting to speculate what the consequences of the existence of such a length scale would be for models of large extra dimensions, in particular, the ADD model. When ADD model is conflated with the minimal length scale scenario, processes involving virtual exhange of gravitons cease to be ulraviolent divergent. We study the production of dileptons at hadron colliders as an example of a process mediated by virtual gravitons. We find that the bounds we derive on the effective string scale are significantly diff…
Electromagnetic radiation from the quark-gluon plasma (QGP) is an important observable to be considered in heavy ion collision experiments. I will provide an update on recent advancements from perturbation theory and quenched lattice simulations. The resummed next-to-leading order (NLO) emission rate has recently been decomposed into transverse and longitudinal components, and extended to non-zero baryon chemical potential. The associated spectral function has also been tested against the Euclidean correlator, for continuum-extrapolated lattice data (at $μ_{\rm B}=0$).
Assuming that in the hot dense matter produced in relativistic heavy-ion collisions, the energy density, entropy density, and pressure as well as the azimuthal and space-time rapidity components of the shear tensor are uniform in the direction transversal to the reaction plane, we derive a set of schematic equations from the Isreal-Stewart causal viscous hydrodynamics. These equations are then used to describe the evolution dynamics of relativistic heavy-ion collisions by taking the shear viscosity to entropy density ratio of $1/4π$ for the initial quark-gluon plasma (QGP) phase and of ten tim…
The significance of thermal dilepton radiation at intermediate invariant masses (1GeV<M<3GeV) in ultrarelativistic heavy-ion collisions is investigated. At CERN-SpS energies, a consistent explanation of the excess observed by NA50 can be given. At RHIC energies the thermal signal is dominated by early emission indicative for QGP formation. Chemical under-saturation effects and the competition with open-charm contributions are addressed.
Dileptons, as an electromagnetic probe, are crucial to study the properties of a Quark-Gluon Plasma (QGP) created in heavy ion collisions. We calculated the invariant mass spectra and the anisotropic emission of thermal dielectrons from Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) energy $\sqrt{s_{NN}}=200$~GeV based on EPOS3. This approach provides a realistic (3+1)-dimensional event-by-event viscous hydrodynamic description of the expanding hot and dense matter with a very particular initial condition, and a large set of hadron data and direct photons (besides $v_{2}$ and $…
Electromagnetic tomography of radial flow in the quark-gluon plasma
Department of Physics, University of California, Berkeley（加州大学伯克利分校物理系）；Nuclear Science Division, Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室核科学部）；Department of Physics, The Ohio State University（俄亥俄州立大学物理系）
The properties of thermal dilepton production from heavy-ion collisions in the RHIC energy regime are evaluated for invariant masses ranging from 0.5 to 3 GeV. Using an expanding thermal fireball to model the evolution through both quark-gluon and hadronic phases various features of the spectra are addressed. In the low-mass region, due to an expected large background, the focus is on possible medium modifications of the narrow resonance structures from $ω$ and $ϕ$ mesons, whereas in the intermediate-mass region the old idea of identifying QGP radiation is reiterated including effects of chemi…
We calculate the yield of lepton pair production from jet-plasma interaction where the plasma is anisotropic in momentum space. We compare both the $M$ and $p_T$ distributions from such process with the Drell-Yan contribution. It is observed that the invariant mass distribution of lepton pair from such process dominate over the Drell-Yan up to $3$ GeV at RHIC and up to $10$ GeV at LHC. Moreover, it is found that the contribution from anistropic quark gluon plasma (AQGP) increases marginally compared to the isotropic QGP. In case of $p_T$-distribution we observe an increase by a factor of $3-4$…
After the discovery of the Quantum Chromodynamics (QCD), many experimental and theoretical efforts have been made to investigate physics issues involved in ultra relativistic heavy-ion collisions. The fundamental goal of this work is to present a short guide of the underlying theory of strong interactions with emphasis on the light vector mesons based on the exceptional work of R.Rapp and J.Wambach. Today widely believed that deconfinement and chiral symmetry restoration probably takes place in a hot and dense hadronic medium as this produced at these collisions. We focus at the place where th…
The dilepton invariant mass spectrum measured in heavy-ion collisions includes contributions from important QGP probes such as thermal radiation and the quarkonium ($J/ψ$, $ψ'$ and $Υ$) states. Dileptons coming from hard $q \bar q$ scattering, the Drell-Yan process, contribute in all mass regions. In heavy-ion colliders, such as the LHC, semileptonic decays of heavy flavor hadrons provide a substantial contribution to the dilepton continuum. The dilepton continuum can give quantitative information about heavy quark yields and their modification in the medium and thus it is important to know al…
The alignment phenomenon, that the 125 GeV $h^0$ boson so resembles the Standard Model Higgs boson, can be understood in a two Higgs doublet model without discrete symmetry. New Yukawa couplings $ρ_{tt}$ and $ρ_{tc}$ offer new avenues to discover the extra scalar $H^0$ and pseudoscalar $A^0$. We propose to search for $cg \to tH^0$, $tA^0$ followed by $H^0$, $A^0 \to t\bar t$, $t\bar c$, where same-sign dileptons could be the harbinger, with triple-top, in the signature of three leptons plus three $b$-jets, as confirmation. Discovery could touch upon the origin of baryon asymmetry of the Univer…
Dilepton production in In+In collisions at 158 AGeV is studied within the microscopic parton-hadron-string dynamics (PHSD) transport approach that incorporates explicit partonic degrees-of-freedom, dynamical hadronization as well as the more familiar hadronic dynamics in the final reaction stages. A comparison to the data of the NA60 Collaboration shows that the measured dilepton yield is well described by including the collisional broadening of vector mesons, while simultaneously accounting for the electromagnetic radiation of the strongly coupled quark-gluon plasma (sQGP) via off-shell quark…
Thermal dilepton radiation from the hot fireballs created in high-energy heavy-ion collisions provides unique insights into the properties of the produced medium. We first show how the predictions of hadronic many-body theory for a melting $ρ$ meson, coupled with QGP emission utilizing a modern lattice-QCD based equation of state, yield a quantitative description of dilepton spectra in heavy-ion collisions at the SPS and the RHIC beam energy scan program. We utilize these results to systematically extract the excess yields and their invariant-mass spectral slopes to predict the excitation func…
We attempt to understand the low-mass dielectron enhancement observed by PHENIX Collaboration at Relativistic Heavy Ion Collider (RHIC) by transport peak in the spectral function. On the basis of the second-order formalism of relativistic dissipative hydrodynamics, we parameterize the spectral function in low-frequency and long-wavelength region by two transport coefficients, electric diffusion coefficient $D$ and relaxation time $τ_{\rm J}$, and compared our theoretical dielectron spectra with the experimental data. We study spectrum of dielectrons produced in relativistic heavy ion collision…
We study the variation of elliptic flow of thermal dileptons with transverse momentum and invariant mass of the pairs for Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. The dilepton productions from quark gluon plasma (QGP) and hot hadrons have been considered including the spectral change of light vector mesons in the thermal bath. The space time evolution has been carried out within the frame work of 2+1 dimensional ideal hydrodynamics with lattice+hadron resonance gas equation of state. We find that a judicious selection of invariant mass(M) and transverse momentum (p_T) windows can be use…
We show that the dilepton spectra measured by the CERES collaboration in Pb + Au interactions for various charge multiplicities can be reproduced by a hadronic initial state with reduction in the masses of the vector mesons in the thermal bath. Though such an effect may also be achieved by a large broadening of the spectral function we show that the photon spectra is insensitive to this. It is found that for higher multiplicities a good description of the data can also be obtained with quark gluon plasma initial state if the reduction of the vector meson masses in the mixed and hadronic phases…
At high temperatures and densities the nuclear matter undergoes a phase transition to a new state of matter called quark gluon plasma (QGP). This new state of matter which existed in the universe after a few microsecond of the big bang can be created in the laboratory by colliding two nuclei at relativistic energies. In this presentation we will discuss how the the properties of QGP can be extracted by analyzing the spectra of photons, dileptons and heavy flavours produced in nuclear collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies.
We discuss the emission of high momentum lepton pairs (p_T>4 GeV) with low invariant masses (M << p_T) in central Au+Au collisions at RHIC (\sqrt{s_{NN}}=200 GeV). The spectra of dileptons produced through interactions of quark and antiquark jets with the quark-gluon plasma (QGP) have been calculated. Annihilation and Compton scattering processes, as well as processes benefitting from collinear enhancement, including Landau-Pomeranchuk-Migdal (LPM) effects, are calculated and convolved with a one dimensional hydrodynamic expansion. The jet-induced contributions are compared to thermal dilepton…
Virtual photon bremsstrahlung in a magnetized quark-gluon-plasma
Institute of Theoretical Physics, University of Wrocław（弗罗茨瓦夫大学理论物理研究所）；Polish Academy of Sciences PAN（波兰科学院）；International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM 2 ), Hiroshima University（广岛大学缠绕手性超物质可持续国际研究所）
We propose a novel method for probing sleptons in compressed spectra at hadron colliders. The process under study is slepton pair production in R-parity conserving supersymmetry, where the slepton decays to a neutralino LSP of mass close to the slepton mass. In order to pass the trigger and obtain large missing energy, an energetic mono-jet is required. Both leptons need to be detected in order to suppress large standard model backgrounds with one charged lepton. We study variables that can be used to distinguish the signal from the remaining major backgrounds, which include tt, WW+jet, Z+jet,…
We address dilepton production in Au+Au collisions at sqrt(s_NN)=200 GeV by employing the parton-hadron-string dynamics (PHSD) off-shell transport approach. Within the PHSD one goes beyond the quasiparticle approximation by solving generalized transport equations on the basis of the off-shell Kadanoff-Baym equations for the Green's functions in the phase-space representation. The approach consistently describes the full evolution of a relativistic heavy-ion collision from the initial hard scatterings and string formation through the dynamical deconfinement phase transition to the quark-gluon p…
We discuss low mass dilepton rates ($\le 1$ GeV) from the deconfined phase of QCD using both perturbative and non-perturbative models and compare with those from lattice gauge theory and in-medium hadron gas. Our analysis suggests that the rate at very low invariant mass ($ M\le 200$ MeV) using the nonperturbative gluon condensate in a semiempirical way within the Green function dominates over the Born-rate and independent of any uncertainty associated with the choice of the strong coupling in perturbation theory. On the other hand the rate from $ρ-q$ interaction in the deconfined phase is imp…
In this review we address the dynamics of relativistic heavy-ion reactions and in particular the information obtained from electromagnetic probes that stem from the partonic and hadronic phases. The out-of-equilibrium description of strongly interacting relativistic fields is based on the theory of Kadanoff and Baym. For the modeling of the partonic phase we introduce a dynamical quasiparticle model (DQPM) for QCD in equilibrium. The widths and masses of the quasiparticles are controlled by transport coefficients in comparison to lattice QCD results. The resulting off-shell transport approach …
The time-scales of rehadronization are considered for a baryon-free QGP at RHIC and LHC energies. The non-equilibrium nucleation scenario leads to mechanical instability of the supercooled QGP phase which then may be suddenly converted in a timelike deflagration from the supercooled state to a (super)heated hadronic matter. In a model simulation such a sudden process was indeed possible and satisfied energy and momentum conservation with non-decreasing entropy. It is possible to reach a hadronic state frozen out immediately after the timelike deflagration. If a TD leads to a simultaneous hadro…
Coarse-grained output from transport calculations is used to determine thermal dilepton emission rates by applying medium-modified spectral functions from thermal quantum field theoretical models. By averaging over an ensemble of events generated with the UrQMD transport model, we extract the local thermodynamic properties at each time step of the calculation. With an equation of state the temperature $T$ and chemical potential $μ_{\mathrm{B}}$ can be determined. The approach goes beyond simplified fireball models of the bulk-medium evolution by treating the full (3+1)-dimensional expansion of…
We study a simple ultraviolet(UV) complete and anomaly free $Z'$ model based on a U$(1)'$ gauge family symmetry without introducing extra fermions beyond the standard model. The U$(1)'$ group is diagonal in the three family space in which the U(1)$'$ charges of the first and second families are the same but different from those of the third family. After spontaneous symmetry breaking and rotating to the mass eigenstates of quarks and leptons, there exist in general both flavor-conserving and flavor-changing couplings. In flavor conserving case, we use the latest dijet and dilepton search at th…
Heavy-ion collisions at very high colliding energies are expected to produce a quark-gluon plasma (QGP) at the highest temperature obtainable in a laboratory setting. Experimental studies of these reactions can provide an unprecedented range of information on properties of the QGP at high temperatures. We report theoretical investigations of the physics perspectives of heavy-ion collisions at a future high-energy collider. These include initial parton production, collective expansion of the dense medium, jet quenching, heavy-quark transport, dissociation and regeneration of quarkonia, photon a…
We investigate the potential of LHC resonance searches in leptonic final states to probe the $Z'$ in the minimal $U(1)_{B-L}$ model. Considering the current constraints on the $Z'$ in terms of its mass $m_{Z'}$ and the associated gauge coupling $g_{B-L}$ as well as constraints in the Higgs sector, we analyse the potential of dilepton and four lepton final states for $Z'$ production. This includes Drell-Yan production, Higgs mediated decays and final state radiation processes concentrating only on the ATLAS and CMS detectors at the LHC. We show that the four-lepton final state is sensitive to $…
