The dark photon is a new gauge boson which arises from an extra U'(1) gauge symmetry. In this paper, a novel dark photon production mechanism based on MeV-scale $γ$-$γ$ collider is considered: $γγ\rightarrow γA'$. With the aid of PACKAGE-X, differential cross section of $γγ\rightarrow γA'$ is obtained, as a function of the kinetic mixing parameter $\varepsilon$ and dark photon mass $m_{A'}$. Taking the light-by-light scattering as background, the constraints on the dark photon parameter space for different time intervals in a MeV-scale $γ$-$γ$ collider are also given.
Production of $ρ(770)$, $η$ pairs at colliding of electron-positron beams and in the decays $ρ(1450)\rightarrow ρ(770)η$, $τ\rightarrow ρ(770)ην_τ$ is calculated in the framework of the Nambu - Jona-Lasinio model. In the process of electron-positron annihilation and the $τ$ - lepton decay the contributions of the intermediate $ρ(770)$ vector meson in the ground and first radially excited state are taken into account. The theoretical prediction for the decay $τ\rightarrow ρ(770)ην_τ$ is given. The obtained results for other processes are in satisfactory agreement with the experimental data.
It is shown that $BR(χ_{b1}(1P)\rightarrow Z\rightarrow e^+e^-)\simeq 3.3\cdot 10^{-7}$, $BR(χ_{b1}(2P)\rightarrow Z\rightarrow e^+e^-)\simeq 4.1\cdot 10^{-7}$ and $BR(χ_{c1}(1P)\rightarrow Z\rightarrow e^+e^-)\simeq 10^{-8}$ that give a good chance to search for the direct production of pseudovector $^3P_1$ heavy quarkonia in $e^+e^-$ collisions ($e^+e^-\rightarrow Z\rightarrow ^3P_1$) even at current facilities not to mention $b$ and $c-τ$ factories.
The phenomenological implications to the decay of the neutral pion from the introduction of new dark particles are discussed. We calculate the contribution to the $π^0$ decay width and then we extend the theory by adding dark sector vector particles which interact through $γ^μ$, $σ^{μν}$ and $σ^{μν}γ^5$. We calculate the total decay width of $π^0\rightarrow γe^+ e^-$ where the electron-positron pair is produced through a decay of a dark meson. The implication of the presented model on the present and future searches for new dark particles is also discussed.
It is shown that $BR(χ_{b1}(1P)\rightarrow Z\rightarrow e^+e^-)\simeq 3.3\cdot 10^{-7}$, $BR(χ_{b1}(2P)\rightarrow Z\rightarrow e^+e^-)\simeq 4.1\cdot 10^{-7}$ and $BR(χ_{c1}(1P)\rightarrow Z\rightarrow e^+e^-)\simeq 10^{-8}$ that give a good chance to search for the direct production of pseudovector $^3P_1$ heavy quarkonia in $e^+e^-$ collisions ($e^+e^-\rightarrow Z\rightarrow ^3P_1$) even at current facilities not to mention $b$ and $c-τ$ factories. Leading radiative corrections to annihilation of quarkonia in QCD are discussed.
The complete matrix element for $e^+e^-\ar b\bar bW^+W^-$ has been computed at tree--level and applied to $Z^0H^0$ production followed by $Z^0\ar b\bar b$ and $H^0\ar W^+W^-$, keeping into account all irreducible backgrounds, which are dominated by \ttb production, at the Next Linear Colliders. We find that, depending on the center of mass energies and on the search strategies, this channel can be useful for the study of the parameters of the Standard Model Higgs boson over the most part of the heavy mass range.
We study the production of a tensor glueball in the reaction $γγ\rightarrow G_2π^0$. We compute the cross section at higher momentum transfer using the collinear factorisation approach. We find that for a value of the tensor gluon coupling of $f^T_g\sim 100$~MeV, the cross section can be measured in the near future by the Belle~II experiment.
We present predictions for the inclusive productions of the D meson originating from bottom hadrons at the CERN LHC in the general-mass variable-flavour-number scheme at next-to-leading order. We present results using two methods to describe the transition for $b\rightarrow D$: a two-step transition $b\rightarrow B \rightarrow D$, based on the $b\rightarrow B$ fragmentation functions and the spectra for $B\rightarrow D$ as measured by CLEO and a one-step transition based on the fragmentation functions for $b\rightarrow D$. The results of both approaches are compared.
We propose a new search for Dark Matter at the LHC, characteristic of scenarios beyond the Standard Model with a pseudoscalar portal between the visible and dark sectors. This search, leading to a $\bar{b} b Z( \rightarrow \ell\ell) + E_{T} \hspace{-4mm}/\hspace{2mm}$ final state, reaches large regions of parameter space not probed by Dark Matter searches via multi-jet $+ E_{T} \hspace{-4mm}/\hspace{2mm}$, searches for new scalars and flavour bounds. We show that this search could be used to test the Dark Matter origin of the gamma ray Galactic Centre excess with LHC Run 2 data.
We have investigated the cross section for the $π^-p\rightarrow K^0πΣ$ and $pp\rightarrow pK^+πΣ$ reactions paying attention to a mechanism that develops a triangle singularity. The triangle diagram is realized by the decay of a $N^*$ to $K^*Σ$ and the $K^*$ decay into $πK$, and the $πΣ$ finally merges into $Λ(1405)$. The mechanism is expected to produce a peak around $2140$ MeV in the $KΛ(1405)$ invariant mass. We found that a clear peak appears around $2100$ MeV in the $KΛ(1405)$ invariant mass which is about $40$ MeV lower than the expectation, and that is due to the resonance peak of a $N^…
Adding a scalar singlet provides one of the simplest extensions of the Standard Model. In this work we briefly review the latest constraints on the mass and mixing of the new Higgs boson and study its production and decay at the LHC. We mainly focus on double Higgs production in the $hh \rightarrow b \bar{b} WW \rightarrow b \bar{b} \ell^+ ν\ell^- \barν$ decay channel. This decay is found to be efficient in a region of masses of the heavy Higgs boson of 260 - 500 GeV, so it is complementary to the 4$b$ channel, more efficient for Higgs bosons having masses greater than 500 GeV. We analyse this…
The potentialities of the production of the scalar $K\bar K$ molecules in the $ϕ$ radiative decays are considered beyond the narrow resonance width approximation. It is shown that $BR(ϕ\rightarrowγf_0(a_0)\rightarrowγππ(πη))\approx (1÷2)\times 10^{-5}\ ,\BR(ϕ\rightarrowγ(f_0+a_0)\rightarrowγK^+K^-)\alt 10^{-6}$ and $BR(ϕ\rightarrowγ(f_0+a_0) \to γK^0\bar K^0)\alt 10^{-8}$. The mass spectra in the $ππ ,\ πη ,\ K^+K^-\ ,\ K^0\bar K^0$ channels are calculated. The imaginary part of the amplitude $ϕ\rightarrowγf_0(a_0)$ is calculated analytically. It is obtained the phase of the scalar resonance p…
In the framework of the littlest Higgs model with T-parity(LHT), we investigate the double Higgs production processes $e^{+}e^{-}\rightarrow ZHH$ and $e^{+}e^{-}\rightarrow ν\barνHH$ at high energy $e^{+}e^{-}$ colliders. We calculate the production cross sections and find that the relative correction at the center-of-mass energy $\sqrt{s}=500$ GeV can maximally reach $-30%$ for the process $e^{+}e^{-}\rightarrow ZHH$ and $-16%$ for the process $e^{+}e^{-}\rightarrow ν\barνHH$ in the allowed parameter space, respectively. These large relative corrections can reach the detection range of the fu…
In this paper, we study the single top production in association with a Higgs boson in the $U(1)_{B-L}$ extension of the Standard Model at the LHC. We calculate the production cross sections of the processes $pp\rightarrow thX(h=H_{1},H_{2};X=j,b,W)$ in this model. Then we further study the observability of the process $pp\rightarrow tH_{2}j$ through $pp\rightarrow t(\rightarrow q\bar{q'} b)H_{2}(\rightarrow 4\ell)j$. We find that the systematic significance can be improved obviously, but it is still challenging for the 14 TeV LHC with high-luminosity to detect this signal.
Motivated by recent search results for the standard model (SM) Higgs boson at the Large Hadron Collider (LHC), we revisit the Higgs phenomenology in the littlest Higgs model with T-parity (LHT). We present the signal strength modifier $μ$ respectively for the main search channels $qq' \rightarrow jjh\rightarrow jjγγ$, $qq'\rightarrow Vh\rightarrow Vγγ$, $qq'\rightarrow Vh \rightarrow Vbb$, $gg\rightarrow h \rightarrow γγ$, and $gg \rightarrow h \rightarrow VV$ in the LHT model. It is found that an enhancement factor of $1.09-1.56$ in $qq' \rightarrow jjh\rightarrow jjγγ$ channel can be obtaine…
In the framework of the minimal $U(1)_{B-L}$ extension of the Standard Model, we investigate the Higgs boson production processes $e^{+}e^{-}\rightarrow ZH$, $e^{+}e^{-}\rightarrow ν_{e}\bar{ν_{e}}H$, $e^{+}e^{-}\rightarrow t\bar{t}H$, $e^{+}e^{-}\rightarrow ZHH$ and $e^{+}e^{-}\rightarrow ν_{e}\bar{ν_{e}}HH$ at the International Linear Collider (ILC). We present the production cross sections, the relative corrections and compare our results with the expected experimental accuracies for Higgs decay channel $H\rightarrow b\bar{b}$. In the allowed parameter space, we find that the effects of the…
Crude estimates are made of the branching ratios and pair production cross-section for our previously proposed bound state S of six top and six antitop quarks identified with the diphoton excess recently observed in ATLAS and CMS. We estimate the pair production cross section to be approximately 12 times that for fourth family quarks. Hence we predict $σ(pp \rightarrow SS + anything) \approx 2$ pb at 13 TeV and an increase by a factor 10 over the cross section at 8 TeV. Crude estimates of the main branching ratios relative to the diphoton decay give $Γ(S\rightarrow γ+γ) \propto 1$, $Γ(S\righta…
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…
The electroweak production processes of vector bosons, $e^+ e^- \rightarrow Z γ$, $γe \rightarrow Ze$, and $γe \rightarrow W ν$ are considered simultaneousely and in the Standard model the covariant polarization density matrices of vector bosons for these processes are obtained explicitly from one of the processes, $γe \rightarrow Z e$. The effect of the photon polarization as well as the vector meson polarization is considered and some special cases are discussed.
We calculate the direct production rate of $J/ψ$ in top quark decays. The color-octet $J/ψ$ production via $t\rightarrow W^+ b J/ψ$ is shown to have a large branching ratio of order $1.5\times 10^{-4}$, which is over an order of magnitude higher than that of the color-singlet $J/ψ$ production via $t\rightarrow W^+ b J/ψ~g~g $ or $t\rightarrow W^+ b~χ_{cJ}~g$ followed by $χ_{cJ}\rightarrow J/ψ~γ$. This result can be used as a powerful tool to test the importance of the color-octet mechanism in heavy quarkonium production.
We evaluate the feasibility of measuring the $Z$ polarization from a heavy Higgs signal in the decay channel $H\rightarrow ZZ \rightarrow \ell^+ \ell^-ν\barν$. Including gluon fusion production of the Higgs, continuum production of $Z$ pairs and the QCD background of single $Z$ production with a missing jet, we find that the average value of a new variable to measure the $Z$ polarization, as a function of transverse mass, will demonstrate the existence of a Higgs boson for heavy Higgs masses up to 800 GeV at the LHC with an integrated luminosity of 10$^5$ pb$^{-1}$.
We study the $D_s^+ \rightarrow π^+ \, π^+ \, π^-$ and $D_s^+ \rightarrow π^+ \, K^+ \, K^-$ decays adopting a mechanism in which the $D_s^+$ meson decays weakly into a $π^+$ and a $q\bar{q}$ component, which hadronizes into two pseudoscalar mesons. The final state interaction between these two pseudoscalar mesons is taken into account by using the Chiral Unitary approach in coupled channels, which gives rise to the $f_0(980)$ resonance. Hence, we obtain the invariant mass distributions of the pairs $π^+ π^-$ and $K^+ K^-$ after the decay of that resonance and compare our theoretical amplitude…
We investigate production and decay of the $Λ_c^+ $ hyperon. The production considered is through the $e^+e^-$ annihilation channel, $e^+e^-\rightarrowΛ_c^+ \barΛ_c^-$, with summation over the $\barΛ_c^- $ anti-hyperon spin directions. It is in this situation that the $Λ_c^+ $ decay chain is identified. Two kinds of sequential decays are studied. The first one is the doubly weak decay $B_1\rightarrow B_2 M_2$, followed by $B_2 \rightarrow B_3 M_3$. The other one is the mixed weak-electromagnetic decay $B_1\rightarrow B_2 M_2$, followed by $B_2 \rightarrow B_3 γ$. In both schemes $B$ denotes ba…
Event rates for dark matter detectors in neutralino--nucleus scattering are studied for supergravity unified models, including the constraint arising from the $b\rightarrow sγ$ experiment. The recent experimental measurement of this decay by the CLEO Collaboration leads to strong constraints on the SUSY particle spectrum,and also significantly affects the event rates in dark matter detectors. The analysis given here uses the accurate method for the computation of the relic density and leads to a dip in the event rate when the neutralino mass is $\sim M_Z/2$ due to the $Z$-pole, and similar res…
In this work, we introduce an extra singlet pseudoscalar into the Type-III two Higgs doublet model (2HDM) which is supposed to solve a series of problems in the modern particle-cosmology. With existence of a light pseudoscalar, the $h\rightarrowμτ$ excess measured at CMS and as well as the $(g-2)_μ$ anomaly could be simultaneously explained within certain parameter spaces that can also tolerate the data on the flavor-violating processes $τ\rightarrowμγ$ and Higgs decay gained at LHC. Within the same parameter spaces, the DM relic abundance is well accounted. Moreover, the recently observed Gal…
The problem of CP conservation and CP violation for two heavy neutrinos production in $e^+e^-$ interaction is considered. Very convenient way of parametrization of the neutrino mass matrix, from which necessary and sufficient condition for CP conservation easily follows, is presented. Contrary to the Kobayashi-Maskawa mechanism, the effects of CP violation in the lepton sector with Majorana neutrinos can be very large. Change of the total cross section caused by CP violation can be much larger then the cross section itself.
The pair production of charged heavy leptons via two photon fusion is considered for hadron collisions at SSC and LHC energies. Rates for the inelastic process $pp \rightarrow γγX \rightarrow L^+L^-X$ and the elastic process $pp \rightarrow γγpp \rightarrow L^+L^- pp$ are given in a Weizsäcker-Williams approximation and compared with production via the gluon fusion and Drell-Yan mechanisms
We compute the contribution of the decays $K_L \rightarrow π^0 Q \bar Q$ and $K^+ \rightarrow π^+ Q \bar Q$, where $Q$ is a dark fermion of the dark sector, to the measured widths for the rare decays $K^+\rightarrow π^+ ν\bar ν$ and $K_L\rightarrow π^0 ν\bar ν$. The recent experimental limit for $Γ(K^+ \rightarrow π^+ ν\bar ν)$ from NA62 sets a new and very strict bound on the dark-sector parameters. A branching ratio for $K_L \rightarrow π^0 Q \bar Q$ within the reach of the KOTO sensitivity is possible. The Grossman-Nir bound is weakened by the asymmetric effect of the different kinematic cu…
We examine the spin-dependence of standard model Higgs boson production at large transverse momentum via the processes $gg \rightarrow gH^0$, $qg \rightarrow qH^0$, and $q\overline{q} \rightarrow gH^0$. The partonic level spin-spin asymmetries ($\hat{a}_{LL}$) for these processes are large at SSC/LHC energies.
The dominant production mechanism for ${\bar b} c$ bound states in high energy processes is the production of a high energy ${\bar b}$ or $c$ quark, followed by its fragmentation into the ${\bar b} c$ state. We calculate the fragmentation functions for the production of the S-wave states $B_c$ and $B_c^*$ to leading order in the QCD coupling constant. The fragmentation probabilities for ${\bar b} \rightarrow B_c$ and ${\bar b} \rightarrow B_c^*$ are approximately $2.2 \times 10^{-4}$ and $3.1 \times 10^{-4}$, while those for $c \rightarrow B_c$ and $c \rightarrow B_c^*$ are smaller by almost t…
In the littlest Higgs model with T-parity, we study associated production of a Higgs and a single top quark at the 14 TeV LHC. We focus on the Higgs to two photons decay and the semileptonic top decay channel. By performing a fast detector simulation, we find that the $thj$ search in the selected channel can excluded the top partner mass $m_{T_{+}}$ up to 805 (857) GeV for case A (case B) at $2σ$ confidence level at 14 TeV LHC with the integrated luminosity $L= 3 \rm ab^{-1}$.
Dark mesons are bosonic composites of a new, strongly-coupled sector beyond the Standard Model. We consider several dark sectors with fermions that transform under the electroweak group, as arise from a variety of models including strongly-coupled theories of dark matter (e.g., stealth dark matter), bosonic technicolor (strongly-coupled indcued electroweak symmetry breaking), vector-like confinement, etc. We consider theories with two and four flavors under an $SU(N)$ strong group that acquire variously chiral, vector-like, and mixed contributions to their masses. We construct the non-linear s…
Most searches for top partners, $T$, are concerned with top partner pair production. However, as these bounds become increasingly stringent, the LHC energy will saturate and single top partner production will become more important. In this paper we study the novel signature of the top partner produced in association with the SM top, $pp\rightarrow T\overline{t}+t\overline{T}$, in a model where the Standard Model (SM) is extended by a vector-like $SU(2)_L$ singlet fermion top partner and a real, SM gauge singlet scalar, $S$. In this model, $pp\rightarrow T\overline{t}+t\overline{T}$ production …
We investigate a model of dark sector based on non-Abelian $SU(2)_D$ gauge symmetry. This dark gauge symmetry is broken into discrete $Z_2$ via vacuum expectation values of two real triplet scalars, and an $SU(2)_D$ doublet Dirac fermion becomes $Z_2-$odd particles whose lighter component makes stable dark matter candidate. The standard model and dark sector can be connected via the scalar mixing and the gauge kinetic mixing generated by higher dimensional operators. We then discuss relic density of dark matter and implications to collider physics in the model. The most unique signatures of th…
We have analyzed the available data on $p\bar{p}\,\rightarrow\, t\, \bar{t}$ followed by the decays ($t\rightarrow bW^{+},\: \bar{t}\rightarrow \bar{b}W^{-}$) which lead to $e^{\pm}μ^{\mp}2 \mathrm{jets}$ or $l^{\pm}4 \mathrm{jets}$ configurations, using a likelihood method we proposed earlier. The outcome is compared with the recent CDF analysis. In an appendix, we discuss the nature of the additional ``slow'' $μ^{+}$ observed in one CDF dilepton event, concluding that it is most probably a ``tertiary lepton'' resulting from the decay sequence $b\rightarrow c +\mathrm{hadrons}$, followed by $…
In this work we consider pair production of LSP tau-sneutrinos at the Compact Lineer Collider. We assume that tau-sneutrinos decays in to e\textmu pair via RPV interactions. Backgroundless subprocess $e{}^{-}e^{+}\rightarrow\tildeν\bar{\tildeν}\rightarrowμ^{+}μ^{+}e^{-}e^{-}(μ^{-}μ^{-}e^{+}e^{+})$ is analyzed in details. Achievable limits on $Br\,(\tildeν_τ\rightarrowμe)$ at $3σ$ and $5σ$ CL are obtained depending on $\tilde{ν_τ}$ mass.
We analyze the $X(3872)$ production in the processes $ \bar{D} D \rightarrow πX $, $\bar{D}^* D \rightarrow πX $ and $\bar{D}^* D^* \rightarrow πX $, making use of the Heavy-Meson Effective Theory, with an effective Lagrangian built based on chiral $SU(3)_{L} \times SU(3)_{R}$ and heavy quark symmetries. In this scenario, we consider $X$ as a bound state of $D^{*} \bar{D} + c.c.$, including neutral and charged components, and obtain the cross sections the mentioned reactions as function of collision energy.
Considering the constraints of the lepton flavor violating (LFV) processes $μ\rightarrow 3e$ and $τ\rightarrow3μ$ on the LFV couplings $Z'\ell_{i}\ell_{j}$, in the contexts of the $E_{6}$ models, the left-right (LR) models, the "alternative" left-right (ALR) models and the 331 models, we investigate the contributions of the extra gauge boson $Z'$ to the decay rates of the processes $\ell_{i}\rightarrow\ell_{j}ν_{\ell}ν_{\ell}$, $τ\rightarrowμP $ and $P\rightarrow μe$ with $P=π^{0},η$ and $η'$. Our numerical results show that the maximal values of the branching ratios for these processes are no…
We present the double real radiation contributions to the $t \bar t$ hadronic production cross section stemming from the partonic process $gg\rightarrow t\bar{t}q\bar{q}$. We explicitly construct the antenna subtraction terms for this gluon-gluon initiated process starting from the double soft behaviour of the double real radiation matrix elements using soft currents. Those subtraction terms, given in leading and subleading colour contributions, require the use of new genuine NNLO four-parton antenna functions involving massive fermions. Those are also presented together with their infrared li…
We investigate the light charged Higgs boson production via $pp \rightarrow H^\pm h$ at the Large Hadron Collider (LHC) in the Two-Higgs Doublet Model (2HDM) type-I. By focusing on a scenario where $H$ is the observed Higgs boson of mass 125 GeV, we study the aforementioned Higgs boson production channel and explore its bosonic decay $H^\pm \rightarrow W^\pm h$. The latter can have a sizable rate that possibly dominates, over the fermionic decay channels, in several regions of the viable parameter space. We demonstrate that the production process $pp \rightarrow H^\pm h$ followed by $H^\pm \ri…
An analysis of the $b \rightarrow sγ$ is given in supergravity grand unification using the framework of the radiative breaking of the electro-weak symmetry under three separate sets of constraints:1) neutralino relic density does not overclose the universe,2)p-stability constraint, and 3) the combined constraints of p-stability and COBE data .For case 1 it is found that the CLEO II data on the branching ratio already imposes very strong further constraints on dark matter analyses. For case2 the branching ratio is found to lie in the range (1.5-6.3)x$10^{-4}$ and thus the data does not at prese…
In this work, we investigate the Higgs-boson production processes $e^{+}e^{-}\rightarrow ZH$, $e^{+}e^{-}\rightarrow ν_{e}\bar{ν_{e}}H$ and $e^{+}e^{-}\rightarrow e^{+}e^{-}H$ in the littlest Higgs model with T-parity. We present the production cross sections, the relative corrections and some distributions of the final states. In the allowed parameter space, we find that the relative corrections of the three production channels are negative, the relative correction of the $ZH$ production can reach $-7.5\%$ and the relative corrections of the $ν_{e}\bar{ν_{e}}H$ and $e^{+}e^{-}H$ production ca…
By employing the method of differential equations, we compute the various types of two-loop master integrals involved in CP-even heavy quarkonium exclusive production and decays. All the integrals presented in this paper can be casted into canonical forms and expressed in terms of Goncharov polylogarithms and Harmonic polylogarithms. These master integrals are frequently used in the calculation of NNLO corrections of the heavy quarkonium production processes, as $γ^*γ\rightarrow Q\bar{Q}$, $e^+e^-\rightarrow γ+ Q\bar{Q}$, and $H/Z^0\rightarrow γ+ Q\bar{Q}$, and decay processes. They are also a…
The study of the anomalous non-resonant $HH$ production is presented from the point of view of effective field theory (EFT) parameterization. The searches for $pp \rightarrow HH \rightarrow γγWW$, $pp \rightarrow HH \rightarrow γγbb$ and $pp \rightarrow HH \rightarrow bbbb$ processes by ATLAS experiment at the Large Hadron Collider (LHC) are reproduced. The selection efficiencies and exclusion limits on the $HH$ production cross sections for different Beyond Standard Model (BSM) EFT benchmark models are obtained using the fast Monte-Carlo simulation of the ATLAS detector.
Rare decays of light mesons may be a discovery window for a new weakly coupled forces hidden at low energy QCD scale. BES-III Collaboration reported the observation of the rare decay $η'\rightarrowπ^0γγ$. The observed decay width disagrees with the preliminary theoretical estimations. We show that this tension may be attributed to the New Physics, presumably Dark Photon. For completeness, we consider the possible influence of the New Physics on a similar well-measured decay $η\rightarrowπ^0γγ$ and a recently measured one $η' \rightarrow ηγγ$ and show that the impact of the hypothetical Dark Ph…
In the littlest Higgs model with T-parity (LHT), we study the $t$-channel single top production in association with a Higgs boson at 8 and 14 TeV LHC. We find that the cross section can be enhanced obviously in this model compared to the Standard Model. By performing a simple parton-level simulation through $pp\rightarrow t(\rightarrow \ell^{+}νb)h(\rightarrow b\bar{b})j$ at 14 TeV LHC, we find that the observability of the signal is promising in the favorable parameter space.
By employing the differential equations, we compute analytically the elliptic sectors of two-loop master integrals appearing in the NNLO QCD corrections to CP-even heavy quarkonium exclusive production and decays, which turns out to be the last and toughest part in the relevant calculation. The integrals are found can be expressed as Goncharov polylogarithms and iterative integrals over elliptic functions. The master integrals may be applied to some other NNLO QCD calculations about heavy quarkonium exclusive production, like $γ^*γ\rightarrow Q\bar{Q}$, $e^+e^-\rightarrow γ+ Q\bar{Q}$,~and~$H/…
The double Higgs boson production through $e^{+}e^-\rightarrow hhZ$ is analyzed in the minimal supersymmetric extension of the Standard Model(SM) with the local gauge symmetry $U(1)_{B-L}$, where $h$ denotes the lightest Higgs boson with 125 GeV. Considering the constraints from the updated prediction data, we find that the production cross section of this process in the model depends on some parameters strongly.
In this talk I attempt to survey some selected physics issues on radiative interference phenomena in the production of heavy unstable particles. A special emphasis is placed on the reactions $e^+e^- \rightarrow W^+W^- \rightarrow 4$ jets and $e^+e^- \rightarrow t\bar{t} \rightarrow bW^+\bar{b}W^-$. A transparent recipe is given for quantifying the level of suppression of the interference effects in the inclusive production processes. The influence of the $W$ width on the Coulomb corrections to the threshold $W^+W^-$ production is briefly addressed.
In the present work, we investigate the production of $Z_{cs}^+$ in $B^+$ and $B_s^0$ decay, where $Z_{cs}^+$ is assigned as a $D_s^{+} \bar{D}^{\ast0} + D_s^{\ast +}\bar{D}^0$ molecular state. By using an effective Lagrangian approach, we evaluate the branching ratio of $B^0_s\rightarrow K^- Z^+_{cs}$ and $B^+\rightarrow ϕZ^{+}_{cs}$ via the triangle loop mechanism. The estimated branching fractions of $B^0_s\rightarrow K^- Z^+_{cs}$ and $B^+\rightarrow ϕZ^{+}_{cs}$ are an order of $10^{-4} $ and $10^{-5}$, respectively. The ratio of these two branching fraction is estimated to be about 5, wh…
The light axigluon model can explain the Tevatron $t\overline{t}$ forward-backward asymmetry and at the same time satisfy the constraints from the electroweak precision measurement and the $ATLAS$ and $CMS$ data, which induces the flavor changing ($FC$) couplings of axigluon with the $SM$ and new quarks. We investigate the effects of these $FC$ couplings on the s- and t-channel single top productions at the $LHC$ and the $FC$ decays $Z\rightarrow \overline{b}s+b\overline{s}$, $t\rightarrow cγ$ and $cg$. Our numerical results show that the light axigluon can give significantly contributions to …
For an electron-photon collider the complete tree-level cross sections of the reaction $γe \rightarrow νb \bar{b} W$ are computed at center-of-mass energies between 0.5 and 2.0 TeV, for top masses of 160 to 200 GeV and Higgs masses between 80 and 140 GeV within the Standard Model. It is shown that most of the $νb \bar{b}$ events are due to Higgs and $Z/γ^*$ production (with $H, Z/γ^* \rightarrow b \bar{b}$ decay) while top production (with $t \rightarrow bW$ decay) is about 50% smaller. Multiperipheral background and interferences are small, respectively negligible, in the energy range studied…
Composite effective field theory signal from anomalous quartic gauge couplings for $ZZ(\rightarrow\ell\ellνν)jj$ and $Zγ(\rightarrowννγ)jj$ productions
