We propose to utilize the exclusive $Z$-boson rare decays $Z\to Υ(ns)+γ$ to constrain the $Zb\bar{b}$ couplings at the HL-LHC and 100 TeV proton-proton collider. We demonstrate that the event yield of the proposed processes is sensitive to the axial-vector component of the $Zb\bar{b}$ coupling and can provide complementary information to the jet-charge weighted single-spin asymmetry measurement at the EIC and the $gg\to Zh$ production rate measurement at the LHC. By applying the NRQCD factorization formalism, we calculate the partial decay width of $Z\to Υ(ns)+γ$ to the NLO accuracy in strong interaction, which is found to agree with those obtained from the light-cone distribution amplitude approach. We show that the HL-LHC can break the degeneracy of the $Zb\bar{b}$ couplings, as implied by the precision electroweak data at LEP and SLC, if the signal efficiency can be improved by a factor of 1.7 from the present ATLAS analysis at the 13 TeV LHC with an integrated luminosity of $36.1~{\rm fb}^{-1}$.
We consider the time-dependent analysis of rare $B_d$ and $B_s$ decays mediated by $b\to s ν\bar ν$ transitions. The inclusion of time evolution allows us to construct novel observables with specific sensitivity to CP-odd phases in these processes. The sensitivity to CP violation of corresponding time-integrated measurements in presence of flavor-tagging is also explored. We provide precise predictions for these observables in the SM and explore their sensitivity to new CP-violating NP contributions at present and planned future $B$-physics experiments. As such, these observables provide uniqu…
The existence of a dilaton as a pseudo-Nambu-Goldstone boson in spontaneous breaking of scale symmetry is predicted in beyond standard model theories in which electroweak symmetry is broken via strongly coupled conformal dynamics. Such a particle is expected to have a mass below the conformal symmetry breaking scale $f$ and couplings to standard model particles similar to those of the SM Higgs boson. In this paper we estimate, for the first time, the dilaton production in exclusive processes considering Pomeron - Pomeron ($\pom \pom$) and photon - photon ($γγ$) interactions, which are characte…
It is well know that the precise measurement of $H\toγγ$ can generate two degenerate parameter spaces of $Hγγ$ anomalous coupling. We propose to utilize the exclusive Higgs rare decays $H\toΥ(ns)+γ$ to break above mentioned degeneracy and further to constrain the $Hγγ$ anomalous coupling at the HL-LHC. We demonstrate that the branching ratios of $H\toΥ(ns)+γ$ can be significantly enhanced in the non-SM-like parameter space from $H\toγγ$ measurement, due to the destructive interference between the direct and indirect production of $Υ(ns)$ in the SM. By applying the NRQCD factorization formalism…
The current uncertainty on the gluon density extracted from the global parton analysis is large in the kinematical range of small values of the Bjorken - $x$ variable and low values of the hard scale $Q^2$. An alternative to reduces this uncertainty is the analysis of the exclusive vector meson photoproduction in photon - hadron and hadron - hadron collisions. This process offers a unique opportunity to constrain the gluon density of the proton, since its cross section is proportional to the gluon density squared. In this paper we consider current parametrizations for the gluon distribution an…
We analyze the possibility of probing anomalous Higgs couplings in the rare decays $H \to Z V$, $V$ being a vector quarkonium state. These rare decays involve both gauge as well as the Yukawa sectors and either of them can potentially be anomalous. We show that the branching fractions for $H \to Z V$ decays in Standard Model are small, making it a sensitive probe for anomalous Higgs couplings originating from physics beyond Standard Model. Moreover, as both $V$ and $Z$ can decay into pair of charged leptons, they provide experimentally clean channels and future LHC runs should observe such dec…
We propose a new scenario of using the dark axion portal at one-loop level to explain the recently observed muon anomalous magnetic moment by the Fermilab Muon g-2 experiment. Both axion/axion-like particle (ALP) and dark photon are involved in the same vertex with photon. Although ALP or dark photon alone cannot explain muon $g-2$, since the former provides only negative contribution while the latter has very much constrained parameter space, dark axion portal can save the situation and significantly extend the allowed parameter space. The observed muon anomalous magnetic moment provides a ro…
We have estimated the sensitivity to the anomalous couplings of the $γγγZ$ vertex in the $γγ\rightarrowγZ$ scattering of the Compton backscattered photons at the CLIC. Both polarized and unpolarized collisions at the $e^+e^-$ energies 1500 GeV and 3000 GeV are addressed, and anomalous contributions to helicity amplitudes are derived. The differential and total cross sections are calculated. We have obtained 95\% C.L. exclusion limits on the anomalous quartic gauge couplings (QGCs). They are compared with corresponding bounds derived for the $γγγZ$ couplings via $γZ$ production at the LHC. The …
Exclusive photoproduction of a $γ\,π^\pm$ pair in the kinematics where the pair has a large invariant mass and the final nucleon has a small transverse momentum is described in the collinear factorization framework. The scattering amplitude is calculated at leading order in $α_s$ and the differential cross sections for the process are estimated in the kinematics of the JLab~12-GeV experiments. The order of magnitude of the predicted cross-sections seems sufficient for a dedicated experiment to be performed. The process turns out to be very sensitive to the axial generalized parton distribution…
Probing anomalous tWb interactions with rare B decays
顶夸克性质的精确研究目前正在LHC和Tevatron对撞机上进行，并有望探测异常的t-W-b相互作用。同时，最近关于B_{d,s}-\bar{B}_{d,s}振荡观测量的实验结果，分支比B_s-> μ ^+ μ ^-，以及B-> K \starl^+ l ^-中的前后不对称性，以及在SM中得到的对相关观测量的精确理论预言，激发了在存在反常t-W-b顶点的情况下对这些观测量的联合研究。我们研究了这种反常耦合对B-> X_s l ^+ l ^-衰变模的贡献，并将它们与B_{d,s}-\bar{B}_d，s，B-> X_s γ观测量的修正相结合，确定了反常t-W-b相互作用实部和虚部的间接界.我们发现这些是最优于目前的直接约束来自顶级衰变和生产测量在LHC和Tevatron。最后，我们预测了B_s-> μ ^+ μ ^-和B-> K ^{（*）} v \bar v的分支比的允许效应，以及B-> K ^* l ^+ l ^-的前后向不对称性。我们发现，在未来这些可观的知识的改进可能会进一步限制一些异常的tWb相互作用。
Rare decay of the Higgs boson is a powerful tool to probe new physics beyond the standard model. The rare decays occur through quantum loops in which the standard model and new physics contributions might cancel each other out. We consider a faked-no-new-physics scenario that the new physics contributions are about minus two times the standard model contribution such that partial widths of Higgs boson rare decays are the same as the standard model predictions. We propose to measure the $HZγ$ and $Hγγ$ anomalous couplings in the process of $e^+ e^- \to Hγ$ that is strongly correlated to Higgs b…
We study the anomalous $W^+W^-V$ ($V=γ,Z$) couplings in $e^+e^-\to W^+W^-$ using the complete set of polarization observables of $W$ boson with longitudinally polarized electron ($e^-$) and positron ($e^+$) beams. For the effective $W^+W^-V$ couplings, we use the most general Lorentz invariant form factor parametrization as well as $SU(2)\times U(1)$ invariant dimension-$6$ effective operators. We estimate simultaneous limits on the anomalous couplings using the Markov-Chain--Monte-Carlo (MCMC) method for an $e^+e^-$ collider running at center of mass energy of $\sqrt{s}=500$ GeV and the integ…
Triple gauge boson production at the LHC can be used to test the robustness of the Standard Model and provide useful information for VBF di-boson scattering measurement. Especially, any derivations from SM prediction will indicate possible new physics. In this paper we present a detailed Monte Carlo study on measuring WWW production in pure leptonic and semileptonic decays, and probing anomalous quartic gauge WWWW couplings at the CERN LHC and future hadron collider, with parton shower and detector simulation effects taken into account. Apart from cut-based method, multivariate boosted decisio…
In this report, we describe the most recent results on exclusive diffraction from the ATLAS, CMS, LHCb, TOTEM experiments at the LHC concerning exclusive pions, $J/Ψ$, $Ψ(2S)$, dilepton, diphoton, $WW$ productions and prospects concerning the search for anomalous couplings and axion-like particle production.
Generalized parton distributions (GPDs) enter QCD factorization theorems for hard exclusive reactions. They encode rich information about hadron partonic structure. We explore a possibility to constrain GPDs in experiments at LHC considering two different exclusive processes: the timelike Compton scattering and the photoproduction of heavy vector mesons.
We propose to measure the $HZγ$ and $Hγγ$ anomalous couplings in the process of $e^{+}e^{-}\rightarrow Hγ$ with the sequential decay of $H\to b{\bar b}$. The discovery potential of observing the anomalous couplings are explored in details. Our study shows that the electron-positron collider has a great potential of testing the $HZγ$ and $Hγγ$ couplings. Conservative bounds on the two anomalous couplings are also derived when no new physics signal were detected on top of the SM backgrounds.
The anomalous quartic neutral couplings of the $γγγγ$ vertex in a polarized light-by-light scattering of the Compton backscattered photons at the CLIC are examined. Both differential and total cross sections are calculated for $e^+e^-$ collision energies 1500 GeV and 3000 GeV. The helicity of the initial electron beams is taken to be $\pm\,0.8$. The unpolarized and SM cross sections for the same values of helicities are also estimated. The 95\% C.L. exclusion limits on two anomalous photon couplings $ζ_1$ and $ζ_2$ are calculated. The best bounds on these couplings are found to be $6.85 \times…
Probing anomalous right--handed current in Z b bbar vertex
由于LEP数据中$Z \to b \bar{b}$衰变的前向-后向不对称性，$-2 σ$偏离了标准模型的预测，我们通过引入$A_{FB}^b$扩展的电弱精度检验来探索$Z b \bar{b}$顶点的异常耦合.我们引入一个新的变量$ε'_b$来测量$Z b \bar{b}$顶点的反常右手耦合。我们的分析对非普适接触相互作用的影响进行了研究，左-右模型也被认为是异常右手耦合的可能起源。
Anomalous couplings of the $Z$ boson to top quarks are only marginally constrained by direct searches and are still sensitive to new particle dynamics at the TeV scale. Employing an effective field theory approach we consider the dimension-six operators which generate deviations from the standard-model vector and axial-vector interactions. We show that rare $B$ and $K$ meson decays together with electroweak precision observables provide strong constraints on these couplings. We also consider constraints from t-channel single-top production.
We extend our studies of a new class of $2 \to 3$ exclusive processes using the collinear factorisation framework by considering the exclusive photoproduction of a $γ\,ρ$ pair, in the kinematics where the pair has a large invariant mass, {and the outgoing $ ρ$-meson has a sufficiently large transverse momentum to not resonate with the nucleon}. We cover the whole kinematical range from medium energies in fixed target experiments to very large energies of colliders, by considering the experimental conditions of JLab~12-GeV, COMPASS, future EIC and LHC (in ultra-peripheral collisions) cases. One…
Probing Weak Anomalous Top Quark Couplings with Final State Gluons at the NLC
过程$e^+e^- \to t\bar tg$的速率和相应的胶子喷流能量分布对顶部与光子和产生顶点处的$Z$的异常偶极耦合的存在敏感。对于这种类型的相当大的反常耦合，很可能与标准模型的预期有很大的偏差。我们探讨的能力的NLC发现或放置这些类型的顶夸克耦合的界限。由此产生的限制被发现是相当互补的那些所产生的直接探针的顶夸克生产顶点。[To出现在{ \it Physics and Technology of the Next Linear Collider}，eds. D. Burke和M. Peskin，1996年提交给Snowmass的报告。
Probing unknown nonperturbative effects in $b \to s \ell\ell$ with inclusive and exclusive observables
Instituto Galego de Física de Altas Enerxías (IGFAE), Universidade de Santiago de Compostela（加利西亚高能物理研究所，圣地亚哥-德孔波斯特拉大学）；Cavendish Laboratory, University of Cambridge（卡文迪许实验室，剑桥大学）；Departament de Física Quántica i Astrofísica, Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona（量子天体物理学系，宇宙科学研究所，巴塞罗那大学）；Physics Department, Indiana University（物理系，印第安纳大学）；Universitat Autònoma de Barcelona（巴塞罗那自治大学）；Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology（高能物理研究所，巴塞罗那科学与技术研究院）
Exclusive production of charmonium-like XYZ states in hadron-hadron ultraperipheral collisions(UPCs) and electron-proton scattering is studied employing effective Lagrangian method. Total cross sections and rapidity distributions of charmonium-like XYZ states are obtained in hadron-hadron UPCs and electron-proton scattering process. These predictions can be applied to estimate the observed event number of exclusive charmonium-like XYZ states in hadron-hadron UPCs and electron-proton scattering. The results indicate that it is significant to search $X(3872)$ and $Z^+_c(3900)$ in pA UPCs and Ele…
Motivated by recent results from the LHCb, BABAR and Belle collaborations on B\to D^{(*)}\ell^-\barν_\ell decays, which significantly deviate from the Standard Model and hint the possible new physics beyond the Standard Model, we probe the R-parity violating supersymmetric effects in B^-_c\to \ell^-\barν_\ell and B\to D^{(*)}\ell^-\barν_\ell decays. We find that (i) \mathcal{B}(B^-_c\to e^- \barν_e) and \mathcal{B}(B^-_c\toμ^-\barν_μ) are sensitive to the constrained slepton exchange couplings; (ii) the normalized forward-backward asymmetries of B\to De^-\barν_{e} decays have been greatly affe…
We study the sensitivity of certain observables to the anomalous right tensorial coupling in single top production at the LHC at $\sqrt{s}=13 \text{ TeV}$. The observables consist of asymmetries constructed from the energy and angles of the decay products of the top quark produced in single top production through $t$-channel. The computation is done at Leading Order (LO) and Next-to-Leading Order (NLO) in the strong coupling in the $5$ flavor scheme. We have estimated projected limits on the anomalous coupling, both at the parton level without cuts and at the particle level with cuts. We find …
