We study the electromagnetic Dalitz decay modes of $J/ψ\rightarrow P l^+l^-$ ($P= π^0$, $η$ or $η^\prime$). In these decays, the lepton pairs are formed by internal conversion of an intermediate virtual photon with invariant mass $m_{l^+l^-}$. Study of the effective-mass spectrum of the $l^+l^-$ will shed light on the dynamic transition form factor $F_{J/ψP}(q^2)$ ($q^2 = m^2_{l^+l^-}$), which characterizes the electromagnetic structure arising at the vertex of the transition $J/ψ$ to pseudoscalars. We also discuss the direct productions of a GeV scale vector $U$ boson in these processes $J/ψ\rightarrow PU$ ($U\rightarrow l^+l^-$). It is responsible for mediating a new $U(1)_d$ interaction, as recently exploited in the context of weakly interacting massive particle dark matter.
In this paper, we firstly use the usual pole approximation for the form factor to estimate the decay rate of $J/ψ\rightarrow P l^+l^-$ in the standard model. Then the reach of searching for the dark photon is estimated. We suggest that these Dalitz decays can be used to search for the light $U$ boson in the BESIII experiment with a huge $J/ψ$ data set.
The electromagnetic transition properties of the decuplet to octet baryon ($Δ\rightarrow Nγ$) is studied within the frame work of a hypercentral quark model. The confinement potential is assumed as hypercentral coloumb plus linear potential. The transition magnetic moment and transition amplitude $f_{M_1}$ for the $Δ\rightarrow Nγ$ are in agreement with other theoretical predictions. The present result of the radiative decay width is found to be in excellent agreement with the experimental values reported by the particle data group over other theoretical model predictions.
The two-photon-exchange (TPE) effects in the process $e^+e^- \rightarrow π^+π^-$ at large momentum transfer are discussed within the perturbative QCD (pQCD). The contributions from the twist-2 and twist-3 distribution amplitudes (DAs) of pion are considered in the estimation. Different with the results under the one-photon-exchange (OPE) approximation, the TPE effects result in an asymmetry of the differential cross section on the scattering angle. The precise measurement of this asymmetry by the further experiment is an precise test of pQCD at large momentum transfer. The time-like electromag…
We show that the $J/ψ\rightarrow π^{+} π^{-}$ decay is a reliable source of information for the electromagnetic form factor of the pion at $t=M_{J/ψ}^2=9.6 {\rm GeV}^2$ by using general arguments to estimate, or rather, put upper bounds on, the background processes that could spoil this extraction. We briefly comment on the significance of the resulting $F_π(M_{J/ψ}^2)$.
We study the electromagnetic form factors of $Λ$ hyperon in the timelike region using the recent experimental data in the exclusive production of $\barΛ Λ$ pair in electron-position annihilation. We present a pQCD inspired parametrization of $G_E(s)$ and $G_M(s)$ with only two parameters, and we consider a suppression mechanism of the electric form factor $G_E(s)$ compared to the magnetic form factor $G_M(s)$. The parameters are determined through fitting our parametrization to the effective form factor data in the reaction $e^+e^-\rightarrow \barΛΛ$. Except the threshold region, our parametri…
We discuss the possible searching for the oscillation by coherent $Λ\barΛ$ production in $J/ψ\rightarrow Λ\barΛ$ decay process. The sensitivity of measurement of $Λ- \barΛ$ oscillation in the external field at BES-III experiment is considered. These considerations indicate an alternative way to probe the $ΔB =2$ amplitude in addition to neutron oscillation experiments. Both coherent and time-dependent information can be used to extract $Λ-\barΛ$ oscillation parameter. With one year's luminosity at BES-III, we can set an upper limit of $δm < 10^{-15}$ MeV at 90% confidence level, corresponding …
We report on ongoing work to determine the pion-cloud contribution to the electromagnetic $N\rightarrowΔ$ transition form factors. The starting point is an $SU(6)$ spin-flavor symmetric constituent-quark model with instantaneous confinement that is augmented by dynamical pions which couple directly to the quarks. This system is treated in a relativistically invariant way within the framework of point-form quantum mechanics using a multichannel formulation. The first step is to determine the electromagnetic form factors of the bare particles that consist only of three quarks. These form factors…
We propose to utilize the transverse mass variable $M_{T2}$ and it's descendant $M_{2Cons}$ for constraining the CP admixture of the tau lepton Yukawa coupling at the LHC. We have considered the tau lepton pair produced from the Higgs boson with each tau decays to a charged pion and a neutrino, $τ^{\pm} \rightarrow π^{\pm} ν_τ$. Recently, for this channel, the LHC has employed the impact parameter method to measure the CP mixing angle of tau lepton Yukawa coupling with large uncertainty. The observables we propose here can be measured in the lab frame without the impact parameter measurement a…
We have investigated the electromagnetic moments of the tau lepton in $e^{+}e^{-} \rightarrow e^{+}γ^{*} γ^{*} e^{-}\rightarrow e^{+}τ\barτe^{-}$ process at the CLIC. We have obtained 95% confidence level bounds on the anomalous magnetic and electric dipole moments for various values of the integrated luminosity and the center of mass energy. We have shown that the $e^{+}e^{-} \rightarrow e^{+}γ^{*} γ^{*} e^{-}\rightarrow e^{+}τ\barτe^{-}$ process at the CLIC leads to a remarkable improvement in the existing experimental bounds on the anomalous magnetic and electric dipole moments.
We calculate the electromagnetic (EM) decay widths of the $B^{\pm}_c(2S)$ meson, which is observed recently by the ATLAS Collaboration. The main EM decay channels of this particle are $1{^3S_1}γ$ and $1{P}γ$, which, in literature, are estimated to have the branching ratio of about $1/10$. In this work, we get the partial decay widths: $Γ(2{^1S_0}\rightarrow 1{^3S_1}γ)=0.192$ keV, $Γ(2{^1S_0}\rightarrow 1{P_1}γ) = 2.24$ keV and $Γ(2{^1S_0}\rightarrow 1{P_1^\prime}γ) = 11.4$ keV. In the calculation, the instantaneous approximated Bethe-Salpeter method is used. For the $P$-wave $B_c$ mesons, the …
The Beijing $e^+e^-$-collider (BEPCII) is a double-ring symmetric collider running at center-of-mass energies between 2.0 and 4.6 GeV. This energy range allows the BESIII-experiment to measure baryon electromagnetic form factors in direct $e^+e^-$-annihilation and in initial state radiation processes. In this paper, results on $e^+e^-\rightarrow p\bar{p}$ and $e^+e^-\rightarrow Λ\barΛ$ based on data collected by BESIII in 2011 and 2012 are presented. Expectations from the BESIII high luminosity energy scan from 2015 and from radiative return at different center-of-mass energies are also report…
The radiative decay of the massive neutrino $ν_i \rightarrow ν_j γ$ in a circularly polarized electromagnetic wave is investigated within the Standard theory with lepton mixing. The decay probability in the wave field does not contain a threshold factor $\sim ( 1 - m_i / m_j )$ as opposed to the decay probability in a vacuum or in a constant uniform external field. The phenomenon of the gigantic enhancement ( $\sim 10^{33}$ ) of the neutrino decay probability in external wave field is discovered. The probability of the photon splitting into the neutrino pair is obtained. (Published in Phys.Let…
Sutherland's theorem dictates that the contribution of the electromagnetic interaction to the decay process (η\rightarrow 3π^{0}) is neglected with respect to the one coming from the difference between the up and down quark masses. In the framework of chiral perturbation theory including virtual photons, we calculated the main diagram concerning the exchange of a virtual photon between two intermediate charged pions. The correction induced by this diagram on the slope parameter amounts to (17%) of the correction induced by the pure strong interaction at one-loop level. If this result is mainta…
The determination of the electromagnetic dipole moments of the top quark is one of the most important goals of the top quark physics program in the collider experiments. For this reason, the top quark pair production to investigate the sensitivity on the electric and magnetic dipole moments of the top quark via the process $pp\rightarrow p γp \rightarrow p t \bar{t} X$ at the Large Hadron Collider (LHC), the High-Luminosity Large Hadron Collider (HL-LHC) and High-Energy Large Hadron Collider (HE-LHC) is discussed. We apply pure leptonic and semileptonic decays for top quark pair production in …
In the framework of MSSM the probability of $Z^0$-boson decay to charginos in a strong electromagnetic field, $Z^0\rightarrow χ^{+} χ^{-}$, is analyzed. The method of calculations employs exact solutions of relativistic wave equations for charginos in a crossed electromagnetic field. Analytic expression for the decay width $Γ(Z^{0}\rightarrow χ^{+} χ^{-})$ is obtained at an arbitrary value of the parameter $\varkappa=e m_Z^{-3}\sqrt{-(F_{μν}q^ν)^2}$, which characterizes the external-field strength $F_{μν}$ and $Z^0$-boson momentum $q^ν$. The process $Z^0\rightarrow χ^{+} χ^{-}$ is forbidden in…
We realize a phenomenological study to examine the sensitivity on the magnetic moment and electric dipole moment of the top quark through the processes $γγ\rightarrow t \bar{t}$, $e γ\rightarrow e γ^{*} γ\rightarrow e t \bar{t}$ and $e^{-} e^{+}\rightarrow e^{-} γ^{*} γ^{*} e^{+} \rightarrow e^{-} t \bar{t}e^{+}$ at the CLIC. We find that with a center-of-mass energy of the CLIC-1.4$\hspace{0.8mm}TeV$, integrated luminosity of ${\cal L}=1500\hspace{0.8mm}fb^{-1}$ and CLIC-3$\hspace{1mm}TeV$, integrated luminosity of ${\cal L}=2000\hspace{0.8mm}fb^{-1}$ with systematic uncertainties of $δ_{sys}…
Semileptonic $b \rightarrow s\ell \ell$ processes constitute a good probe for new physics phenomena: new particles contributing to the loops could affect branching fractions and angular distributions, and have different couplings to different lepton families, thus violating lepton flavour universality. Recent results from the LHCb experiment are reviewed.
We investigate the feasibility of distinguishing among different models of electroweak symmetry breaking by studying the process $γγ\rightarrow Z_L Z_L$ at photon colliders. For models with a low mass Higgs-like scalar resonance, the $s$-channel contribution provides a distinct resonance structure and large cross sections. However, the absence of a resonance structure in the cross section for the above process does not discriminate in principle between the existence of either a heavy Higgs boson or a vector resonance of a non-linearly realized symmetry.
We examine the potential of the process $ep \rightarrow eγ^{*} γ^{*} p\rightarrow eτ\barτp$ at the Large Hadron Electron Collider (LHeC) and the Future Circular Hadron Electron Collider (FCC-he) to examine non-standard $τ\barτγ$ coupling in a model independent way by means of the effective Lagrangian approach. We perform pure leptonic and semileptonic decays for $τ^{-}τ^{+}$ production in the final state. Furthermore, we use $L = 10, 50, 100, 300, 500, 1000$ fb$^{-1}$ with at $\sqrt{s}=1.30, 1.98, 7.07, 10$ TeV and we consider systematic uncertainties of $δ_{sys}=0,5,10 \%$. The best sensitivi…
In the framework of the Left-Right twin Higgs (LRTH) model, we consider the constrains from the latest search for high-mass dilepton resonances at the LHC and find that the heavy neutral boson $Z_H$ is excluded with mass below 2.76 TeV. Under these constrains, we study the Higgs-Gauge coupling production processes $e^{+}e^{-}\rightarrow ZH$, $e^{+}e^{-}\rightarrow ν_{e}\bar{ν_{e}}H$ and $e^{+}e^{-}\rightarrow e^{+}e^{-}H$, top quark Yukawa coupling production process $e^{+}e^{-}\rightarrow t\bar{t}H$, Higgs self-couplings production processes $e^{+}e^{-}\rightarrow ZHH$ and $e^{+}e^{-}\rightar…
Low energy observables involving the Standard Model fermions which are chirality-violating, such as anomalous electromagnetic moments, necessarily involve an insertion of the Higgs in order to maintain $SU(2) \times U(1)$ gauge invariance. As the result, the properties of the Higgs boson measured at the LHC impact our understanding of the associated low-energy quantities. We illustrate this feature with a discussion of the electromagnetic moments of the $τ$-lepton, as probed by the rare decay $H \rightarrow τ^+ τ^- γ$. We assess the feasibility of measuring this decay at the LHC, and show that…
We study the effective $B-L$ violating couplings for scalar and vector leptoquarks which can naturally induce dimension seven $B-L$ violating operators leading to very interesting nucleon decay modes such as $n \rightarrow e^- π^+, e^-K^+,μ^- π^+, μ^-K^+$ and $p \rightarrow νπ^+$. This opens a new window to probe the nature and couplings of the scalar and vector leptoquarks in an ultraviolet model independent way which can provide an orthogonal probe for scalar and vector leptoquark solutions to the recent anomalous $B$-decay data. Furthermore, we also discuss how these $B-L$ violating interac…
In this paper, we examine the potentials of the processes $γγ\rightarrow W^{+} W^{-}Z $ and $e^{+}e^{-} \rightarrow e^{+}γ^{*} γ^{*} e^{-} \rightarrow e^{+} W^{+} W^{-} Z e^{-}$ at the CLIC with $\sqrt{s}=0.5,1.5$ and $3$ TeV to investigate anomalous quartic $WWZγ$ couplings by two different CP-violating and CP-conserving effective Lagrangians. We find $95\%$ confidence level limits on the anomalous coupling parameters at the three CLIC energies and various integrated luminosities. The best limits obtained from the process $γγ\rightarrow W^{+} W^{-}Z $ on the anomalous $\frac{k_{0}^{W}}{Λ^{2}}…
In this paper we investigate CP violation in charged decays of $D$ meson. Particularly, we study the direct CP asymmetry of the Cabibbo favored non-leptonic $D^+ \rightarrow \bar K^0 π^+$ and the doubly Cabibbo-suppressed decay mode $D^+ \rightarrow K^0 π^+$ within standard model, two Higgs doublet model with generic Yukawa structure and left right symmetric models. In the standard model, we first derive the contributions from box and di-penguin diagrams contributing to their amplitudes which are relevant to the generation of the weak phases essential for non-vanishing direct CP violation. The…
We estimate the electromagnetic decay rates of $χ_{c0}\rightarrow γγ$ and $χ_{c2}\rightarrowγγ$ by taking into account both relativistic and QCD radiative corrections. The decay rates are derived in the Bethe-Salpeter formalism and the QCD radiative corrections are included in accordance with factorization assumption. Using a QCD-inspired interquark potential, we obtain relativistic BS wavefunctions of $χ_{c0}$ and $χ_{c2}$ by solving BS equations for the corresponding $^{2S+1}L_J$ states. Our numerical result for the ratio $R=\frac{Γ(χ_{c0}\rightarrowγγ)}{Γ(χ_{c2} \rightarrowγγ)}$ is about $1…
In this work we have employed Bethe-Salpeter equation (BSE) under covariant instantaneous ansatz (CIA) to study electromagnetic decays of ground state equal mass vector mesons: $ρ$, $ω$, $ϕ$, $ψ$ and $Y$ through the process $V\rightarrowγ*\rightarrow e^+ + e^-$. We employ the generalized structure of hadron-quark vertex function $Γ$ which incorporates various Dirac structures from their complete set order-by-order in powers of inverse of meson mass. The electromagnetic decay constants for the above mesons are calculated using the leading order (LO) and the next-to-leading order (NLO) Dirac str…
In this work we study the constraints on the anomalous $tqγ$ ($q=u$, $c$) couplings by photon-produced leading single top production and single top jet associated production through the main reaction $pp\rightarrow pγp\rightarrow pt\rightarrow pW(\rightarrow\ell ν_\ell) b+X$ and $pp\rightarrow pγp\rightarrow ptj\rightarrow pW(\rightarrow\ell ν_\ell) bj+X$ assuming a typical LHC multipurpose forward detectors in a model independent effective lagrangian approach. Our results show that: for the typical detector acceptance $0.0015<ξ_1<0.5$, $0.1<ξ_2<0.5$ and $0.0015<ξ_3<0.15$ with a luminosity of …
The study of electromagnetic and weak form factors of nucleon (charged quasielastic scatterings of neutrino (antineutrino) and nucleon) done in $70^\prime s$ and published in Chinese journals is reviewed. In the approach of the study antiquark components are introduced to the wave functions of nucleon and the study shows that the antiquark components of nucleon play an essential role in the EM and weak form factors of nucleon. The SU(6) symmetric wave functions of baryons in the rest frame ( s-wave in the rest frame) have been constructed. In these wave functions there are both quark and antiq…
Basing on the branching fractions of J/ψ\to VP from different experiments, we investigate on the properties of the coupling constants of J/ψ\to VP decays with a model-dependent approach. We find that the octet coupling constant, g_8, of strong interaction is about twice larger than that of the singlet coupling constant g_1; the electromagnetic breaking parameters g^i_E are larger than the mass breaking parameters g^i_M, moreover, the three parameters of electromagnetic effect are about equal, but the three parameters of mass effect are obviously different and their uncertainties are also large…
In the framework of Chiral Perturbation Theory including photons, we found that the contribution of the photon exchange between two intermediate charged Kaons to the slope parameter of the decay (η\rightarrow 3π^{0}) amounts to (-0.0221\pm 0.0034). When compared with the experimental value, (α=-0.0317\pm 0.0016), on the one hand, and with the contribution of the up and down quark mass difference, (+0.013\pm 0.032), on the other hand, our result leads to the direct conclusion: \textit{The} (η\rightarrow 3π^{0}) \textit{decay \uline{cannot} be used to determine} (m_{d}-m_{u}).
It had been suggested to probe CP violation in τ \rightarrow νKπ decays with K0 -K ^{-}0 oscillation to produce ACP(τ- \rightarrow νKSπ-) = (0.36\pm0.01)%. BaBar has found ACP(τ- \rightarrow νKSπ-[\geq π0]) = (-0.36 \pm 0.23 \pm 0.11)% - i.e., 2.8 sigma difference with SM prediction. It is discussed, why one needs to probe ACP(τ \rightarrow νKπ), ACP(τ \rightarrow νK2π) and ACP(τ \rightarrow νK3π) separately to establish the existence of New Dynamics and its features. It should be possible at SuperB & Super-Belle experiments.
We demonstrate experimentally that the trident process $e^-\rightarrow e^-e^+e^-$ in a strong external field, with a spatial extension comparable to the effective radiation length, is well understood theoretically. The experiment, conducted at CERN, probes values for the strong field parameter $χ$ up to 2.4. Experimental data and theoretical expectations using the Local Constant Field Approximation show remarkable agreement over almost 3 orders of magnitude in yield.
We apply a modified vector meson dominance (VMD) model to analyze the electromagnetic form factors of the $Λ_c$ hyperon in the time-like reaction $e^+e^-\rightarrow Λ_c^+ \barΛ_c^-$. In the model, we include the contributions from the vector charmed mesons and their excitations $ψ(1S)$, $ψ(2S)$, $ψ(3770)$, $ψ(4040)$, $ψ(4160)$ and $ψ(4415)$. We perform a combined fit to the available data on the Born cross section in reaction $e^+e^-\rightarrow Λ_c^+ \barΛ_c^-$ and the ratio of the electromagnetic form factors $|G_E/G_M|$ to obtain the values of the model parameters. Our results show that the …
We investigate the radiative $B_{c} \to D_{s1} γ$ transition in the framework of QCD sum rules. In particular, we calculate the transition form factors responsible for this decay in both weak annihilation and electromagnetic penguin channels using the quark condensate, mixed and two-gluon condensate diagrams as well as propagation of the soft quark in the electromagnetic field as non-perturbative corrections. These form factors are then used to estimate the branching ratios of the channels under consideration. The total branching ratio of the $B_{c} \to D_{s1} γ$ transition is obtained to be i…
It is extremely challenging to probe the charm-quark Yukawa coupling at hadron colliders primarily due to the large Standard Model (SM) background (including $h\to b\bar b$) and the lack of an effective trigger for the signal $h\to c\bar c$. We examine the feasibility of probing this coupling at the LHC via a Higgs radiative decay $h\rightarrow c\bar{c}γ$. The existence of an additional photon in the final state may help for the signal identification and background suppression. Adopting a refined triggering strategy and utilizing basic machine learning, we find that a coupling limit of about 8…
In this study, we investigate the potential of the process $pp\rightarrow pγ^{*} p\rightarrow p τ\barν_τq^{\prime} X$ at the LHC to examine the anomalous electromagnetic moments of the tau lepton. We obtain $95\%$ confidence level bounds on the anomalous coupling parameters with various values of the integrated luminosity and center-of-mass energy. The improved bounds have been obtained on the anomalous coupling parameters of electric and magnetic moments of the tau lepton $a_τ$ and $\vert$$d_τ$$\vert$ compared to the current experimental sensitivity bounds. The $γp$ mode of photon reactions a…
An overview of the latest theoretical developments and results on electromagnetic and weak probes in relativistic heavy-ion collisions is presented. The possibilities to use electromagnetic probes, i.e., photons and dileptons, as a spectrometer, thermometer, chronometer, polarimeter, barometer, and multimeter of the collision system, as well as to explore the QCD phase diagram and to locate phase transitions such as the critical endpoint, are discussed.
Recent theoretical developments concerning radiation of electromagnetic and weak probes in ultra-relativistic heavy-ion collisions is overviewed. These proceedings focus on electromagnetic probes and briefly cover weak probes. An outlook regarding the future use of electromagnetic probes is formulated whereby a quantitative Bayesian comparison, simultaneously employing electromagnetic and hadronic calculations of experimental observables against data, is highlighted as a path towards a better understanding of the properties of the QCD medium.
We calculate the electromagnetic corrections to the decays $η\rightarrow 3π$ in next to leading order in the chiral expansion. We find that the corrections are small in accordance with Sutherland's theorem and modify neither rate nor the Dalitz plot distributions noticeably.
The $O(α)$ electromagnetic radiative corrections to the $B^- \rightarrow V^0 \ell^- \barν_{\ell}$ ($V$ is a vector meson and $\ell$ a charged lepton) decay rates are evaluated using the cutoff method to regularize virtual corrections and incorporating intermediate resonance states in the real-photon amplitude to extend the region of validity of the soft-photon approximation. The electromagnetic and weak form factors of hadrons are assumed to vary smoothly over the energies of virtual and real photons under consideration. The cutoff dependence of radiative corrections upon the scale $Λ$ that se…
The QCD sum rule approach to in-medium modifications of the omega meson in nuclear matter is reviewed with emphasis of its relation to 4-quark condensates and chiral symmetry restoration. Possible implications of the CB-TAPS experiment for the reaction gamma A -> A' omega (-> pi0 gamma) are sketched and the particularly important role of di-electron probes, accessible with HADES, is highlighted. A brief update of a parametrization of the previous dilepton and photon probes from CERES and WA98 of heavy-ion collisions at CERN-SPS energies is presented.
We discuss the impact of the presence of a charged Higgs and a $W'$ gauge boson on the tau-neutrino nucleon scattering $ν_τ+ N \rightarrow τ^- + X$ and $\barν_τ+ N \rightarrow τ^+ + X$. We show the effect of the new physics on the three subprocesses quasielastic, $Δ$-resonance, and deep inelastic scattering. The measurement of the atmospheric and reactor mixing angles $θ_{23}$ and $θ_{13}$, respectively, relies on the standard model cross section of the above processes if they have been measured in the appearance channels $ν_μ\rightarrow ν_τ$ and $\barν_e \rightarrow \barν_τ$ ($ν_e \rightarrow…
We introduce the seminal developments in the theory and experiments of electromagnetic probes for the study of the dynamics of relativistic heavy ion collisions and quark gluon plasma.
The penetrating nature of electromagnetic probes makes them an ideal candidate to study properties of the Quark-Gluon Plasma (QGP). A selection of recent developments in the theory and phenomenology of electromagnetic probes is discussed, with an emphasis given towards how these probes can be used to constrain QGP trapnsport coefficients. A Bayesian treatment of electromagnetic radiation, similar to the one of soft hadronic observables and jets, is suggested as a path towards imposing more stringent constraints on various transport coefficients of the QCD medium.
We study the decay $B_c \rightarrow D_s^* γ$. There are two mechanisms contributing to the process. One proceeds through the short distance $b{\rightarrow}sγ$ transition and the other occurs through weak annihilation accompanied by a photon emission.The electromagnetic penguin contribution is estimated by perturbative QCD and found to be $4.68\times10^{-18}$ GeV. In particular, we find the contribution of the weak annihilation is $6.25\times10^{-18}GeV$ which is in the same order as that of the electromagnetic penguin. The total decay rate $Γ(B_c \rightarrow D_s^* γ)$ is predicted to be $1.45\…
We review the current state of research on electromagnetic probes in the context of heavy-ion collisions. The focus is on thermal photons and dileptons which provide unique insights into the properties of the created hot and dense matter. This review is intended to provide an introductory overview of the topic as well as a discussion of recent theoretical and experimental results. In particular, we discuss the role of vector-meson spectral functions in the calculation of photon and dilepton rates and present recent results obtained from different frameworks. Furthermore, we will highlight the …
After a brief reminder on the electromagnetic properties of neutrinos, the main processes of the electromagnetic interactions of neutrinos in astrophysics and the corresponding limitations on millicharges and effective magnetic moments of the particle are discussed.
After pioneering works on hypernuclei, strangeness production mechanisms have been studied in hadron collisions and photoreactions in the sixties. Recent experiments at SATURNE and COSY, in the hadronic sector, as well as ELSA and JLab, in the electromagnetic sector, have confirmed our basic ideas on the reaction mechanisms. In the near future, strangeness production at JLab, HERMES and COMPASS may prove to be a powerful tool to study hadronic matter.
The penetrating nature of electromagnetic signals makes them suitable probes to explore the properties of the strongly-interacting medium created in relativistic nuclear collisions. We examine the effects of the initial conditions and shear relaxation time on the spectra and flow coefficients of electromagnetic probes, using an event-by-event 3+1D viscous hydrodynamic simulation (MUSIC).
We have investigated the electromagnetic decays of the antitriplet and sextet charmed baryon systems with $J^P= \frac{1}{2}^+, \frac{3}{2}^+$ in the framework of the heavy baryon chiral perturbation theory. We first construct the chiral Lagrangians at $O(p^2)$ and $O(p^3)$. Then we calculate the electromagnetic (EM) decay amplitudes of the charmed baryon systems up to $O(p^3)$. With the help of the quark model, we estimate the low energy constants. The numerical results of the EM decay widths show good convergence of the chiral expansion. We notice that the two neutral EM decay processes $Ξ_c'…
The expressions for the differential cross section and of the polarization observables for the reaction $\bar p+p\rightarrow e^++e^-$ are given in terms of the nucleon electromagnetic form factors in the laboratory system. Radiative corrections due to the emission of virtual and real soft photons from the leptons are also calculated. Unlike the center-of- mass system case, they depend on the scattering angle. Polarization effects are derived in the case when the antiproton beam, the target and the electron in the final state are polarized. Numerical estimations have been done for all observabl…
