arXiv subjects

Peng-Cheng Lu

Publications and source records attributed to Peng-Cheng Lu.

13 recordsLinked to original sources

arXiv2025

Muon collider probes of the gluonic quartic gauge couplings

We investigate the dimension-8 gluonic quartic gauge couplings (gQGCs) at future high-energy muon colliders through the process $\mu^{+}\mu^{-}\!\to gg\gamma$. Using detailed event simulation and optimized kinematic selections, we derive projected sensitivities to the Wilson coefficients and their associated new-physics scales, showing that muon colliders can probe deep into the multi-TeV regime and significantly surpass current LHC bounds. We further present the positivity bounds on those Wilson coefficients, as theoretical constraints from the fundamental principles of quantum field theory. Our results establish $\mu^{+}\mu^{-}\!\to gg\gamma$ as one of the most sensitive probes of dimension-8 new physics at future muon colliders.

hep-ph↗

arXiv2025

Study $\gamma\gamma \to \tau^+\tau^-$ process including $\tau^+ \tau^-$ spin information in Pb-Pb ultraperipheral collision and at Lepton collider

We study the $\gamma\gamma \to \tau^+\tau^-$ process including full $\tau^+ \tau^-$ spin information in Pb--Pb ultraperipheral collision and at lepton colliders. We present the predictions for the corresponding cross sections and spin correlations at NLO electroweak precision, and find that the NLO electroweak contributions are numerically small for the observables considered. Additionally, we use the spin correlations obtained in this paper to analyze the quantum entanglement in the $\tau^+\tau^-$ system of the $\gamma\gamma \to \tau^+\tau^-$ process. Our results show that there is a genuine entangled configuration near the $\tau^+\tau^-$ invariant mass threshold. This work is helpful for studying the $\tau$-pair production induced by photon-photon collision at high energy colliders.

hep-ph↗

arXiv2025

Probing the electromagnetic dipole moment of the $\tau$ lepton in the $e^+e^- \to \gamma^*/Z \to \tau^+ \tau^-$ reaction

High-precision measurements of the lepton's electromagnetic dipole moments provide a powerful probe for testing the Standard Model. A non-zero value of the $\tau$ lepton's electric(weak) dipole moment ($d_{\tau}^{\gamma}$, $d_{\tau}^{Z}$) would serve as a smoking gun of the new physics. On the one hand, current and future high energy colliders offer an ideal environment for such measurements. On the other hand, it is essential to investigate the optimal measurement method for extracting not only $d_{\tau}^{\gamma}$ and $d_{\tau}^{Z}$, but also the anomalous magnetic dipole moment ($a_{\tau}$). In this work, we analyze the precision of observables, particularly optimal observables, for determining these physics quantities through the process $e^+e^- \to \gamma^*/Z \to \tau^+ \tau^-$ with $\tau$ leptons undergoing (semi-)leptonic and hadronic decays at the centre-of-mass energies at the Z pole mass and significantly below $m_Z$. By considering the full kinematic information of the decay products, we find that the sensitivities to Im$d_{\tau}$ and Re$d_{\tau}$ can reach $10^{-21}$ $ecm$ at CEPC $\sqrt s = m_Z$, compared to $10^{-20}$ $ecm$ at Belle-II $\Upsilon(4S)$ resonance and $10^{-17}$ $ecm$ at BEPCII $\psi(2S)$ resonance. For $a_{\tau}$, we find that Im$a_{\tau}$ and Re$a_{\tau}$ with a precision of $10^{-5}$ at Belle-II $\sqrt s=10.58$ GeV can be attained.

hep-ph↗

arXiv2024

Flavor Physics at the CEPC: a General Perspective

We discuss the landscape of flavor physics at the Circular Electron-Positron Collider (CEPC), based on the nominal luminosity outlined in its Technical Design Report. The CEPC is designed to operate in multiple modes to address a variety of tasks. At the $Z$ pole, the expected production of 4 Tera $Z$ bosons will provide unique and highly precise measurements of $Z$ boson couplings, while the substantial number of boosted heavy-flavored quarks and leptons produced in clean $Z$ decays will facilitate investigations into their flavor physics with unprecedented precision. We investigate the prospects of measuring various physics benchmarks and discuss their implications for particle theories and phenomenological models. Our studies indicate that, with its highlighted advantages and anticipated excellent detector performance, the CEPC can explore beauty and $\tau$ physics in ways that are superior to or complementary with the Belle II and Large-Hadron-Collider-beauty experiments, potentially enabling the detection of new physics at energy scales of 10 TeV and above. This potential also extends to the observation of yet-to-be-discovered rare and exotic processes, as well as testing fundamental principles such as lepton flavor universality, lepton and baryon number conservation, etc., making the CEPC a vibrant platform for flavor physics research. The $WW$ threshold scan, Higgs-factory operation and top-pair productions of the CEPC further enhance its merits in this regard, especially for measuring the Cabibbo-Kobayashi-Maskawa matrix elements, and Flavor-Changing-Neutral-Current physics of Higgs boson and top quarks. We outline the requirements for detector performance and considerations for future development to achieve the anticipated scientific goals.

hep-ex↗

arXiv2024

NLO EW corrections to tau pair production via photon fusion in Pb-Pb ultraperipheral collision

We study the next-to-leading order (NLO) electroweak (EW) corrections to the $\gamma \gamma \to \tau^+ \tau^-$ process in Pb-Pb ultraperipheral collision (UPC). We find that the EW correction $\delta \sigma_{\mathrm{EW}}$ decreases the total cross section $\sigma_{\mathrm{NLO}} = \sigma_{\mathrm{LO}} + \delta \sigma_{\mathrm{EW}}$ by -3\% at Pb-Pb center-of-mass energy $\sqrt{s_{NN}}=5.02$ TeV. The weak correction plays significant role whose contribution is about -4 times of that of QED. The CMS and ATLAS collaborations use the reaction $\gamma\gamma \to \tau^+ \tau^-$ in Pb-Pb and proton-proton UPC to constrain tau's anomalous magnetic moment $a_\tau$. By parameterizing the $\gamma \tau \tau$ vertex with two form factors $F_{1,2}$, the cross section can be written as $\sigma_{a_\tau} = \sigma_{\mathrm{LO}} + \delta \sigma_{a_\tau}$, where $\delta \sigma_{a_\tau}$ is proportional to $a_\tau$. The impact of NLO EW corrections on $a_\tau$ bounds in Pb-Pb UPC is limited, as the current experimental bounds are loose. We also find that various differential distributions of the two ratios $\mathrm{d} \sigma_{\mathrm{NLO}}/ \mathrm{d} \sigma_{\mathrm{LO}}$ and $\mathrm{d} \sigma_{a_\tau}/ \mathrm{d} \sigma_{\mathrm{LO}}$ have different lineshapes. This work is significant to precisely study the interaction of $\gamma \tau \tau$ via $\gamma \gamma \to \tau^+ \tau^-$ process.

hep-ph↗

arXiv2023

Top and bottom quark forward-backward asymmetries at next-to-next-to-leading order QCD in (un)polarized electron positron collisions

We consider, at order $α_s^2$ in the QCD coupling, top-quark pair production in the continuum at various center-of-mass energies and $b$-quark pair production at the $Z$ resonance by (un)polarized electron and positron beams. For top quarks we compute the forward-backward asymmetry with respect to the top-quark direction of flight, the associated polar angle distribution, and we analyze the effect of beam polarization on the QCD corrections to the leading-order asymmetry. We calculate also the polarized forward-backward asymmetry. For $b$-quark production at the $Z$ peak we explore different definitions of $A_{\rm FB}$. In particular, we analyze $b$ jets defined by the Durham and the flavor-$k_T$ clustering algorithms. We compute the inclusive $b$-jet and two-jet asymmetry with respect to the $b$-jet direction. For the latter asymmetry the QCD corrections to order $α_s^2$ are small. That predestines it to act as a precision observable.

hep-ph↗

arXiv2022

Search for heavy Majorana neutrinos at future lepton colliders

The nonzero neutrino mass can be a signal for new physics beyond the standard model. To explain the tiny neutrino mass, we can extend the standard model with right-handed Majorana neutrinos in a low-scale seesaw mechanism, while the CP violation effect can be induced due to the CP phase in the interference of heavy Majorana neutrinos. The existence of heavy Majorana neutrinos may lead to lepton number violation processes, which can be used as a probe to search for the signal of heavy Majorana neutrinos. In this paper, we focus on the CP violation effect related to two generations of heavy Majorana neutrinos for $15$ GeV $<m_N<$ $70$ GeV in the pair production of W bosons and rare decays. It is valuable to investigate the Majorana neutrino production signals and the related CP violation effects in the W boson rare decays at future lepton colliders.

hep-ph↗

arXiv2022

Measuring CP violation in rare $W$ decays at the LHC

Heavy Majorana neutrinos beyond the standard model can simultaneously explain the origin of tiny neutrino masses and matter-antimatter asymmetry in our Universe. The existence of heavy Majorana neutrinos will also lead to lepton number violation and the rare lepton-number-violating $W$ decays are possible. With contributions from two different Majorana neutrinos, a nonzero CP asymmetry may be generated from the rate difference between $W$ decay and its CP-conjugate process. The aim of this paper is to investigate the prospects for measuring CP violation in rare $W$ decays via Majorana neutrinos at the LHC. Our calculations show that the induced CP asymmetry is independent of the Majorana neutrino mass for $10~ \rm GeV < m_N < 70 ~\rm GeV$. Such a CP asymmetry if observed, would in turn provide unambiguous evidence of new physics beyond the standard model.

hep-ph↗

arXiv2021

Production of excited heavy quarkonia in $e^+e^- \to γ^*/Z^0 \to |(Q\bar{Q})[n]\rangle +γ$ at super $Z$ factory

Within the nonrelativistic quantum chromodynamics framework, we make a comprehensive study on the exclusive production of excited charmonium and bottomonium in $e^+e^-\to γ^*/Z^0 \to|(Q\bar{Q})[n]\rangle +γ$ ($Q=c$ or $b$ quarks) at future $Z$ factory, where the $[n]$ represents the color-singlet $n^1S_0,~n^3S_1,~n^1P_0$ and $n^3P_J$ ($n=1,2,3,4; J=0,1,2$) Fock states. The "improved trace technology" is adopted to derive the analytic expressions at the amplitude level, which is useful for calculating the complicated $nP$-wave channels. Total cross sections, differential distributions, and uncertainties are discussed in system. According to our study, production rates of heavy quarkonia of high excited Fock states are considerable at future $Z$ factory. The cross sections of charmonium for $2S$, $3S$, $4S$, $1P$, $2P$, $3P$ and $4P$-wave states are about $53.5\%$, $30.4\%$, $23.7\%$, $13.7\%$, $6.8\%$, $9.2\%$, and $9.2\%$ of that of the $1S$ state, respectively. And cross sections of bottomonium for $2S$, $3S$, $4S$, $1P$, $2P$, $3P$ and $4P$-wave states are about $39.3\%$, $12.3\%$, $14.3\%$, $7.1\%$, $3.1\%$, $2.7\%$, and $3.1\%$ of that of the $1S$ state, respectively. The main uncertainties come from the radial wave functions at the origin and their derivatives at the origin under different potential models. Then, such super $Z$ factory should be a good platform to study the properties of the high excited charmonium and bottomonium states.

hep-ph↗

arXiv2021

CP violation in top quark decay via heavy Majorana neutrinos at the LHC

The tiny neutrino masses can be explained naturally by extending the standard model with right-handed Majorana neutrinos in low-scale seesaw mechanism, and the CP violation effect induced by Majorana phase is interesting and worth studying at colliders. In this paper, we investigate the prospects for measuring CP violation in top quark pair production and rare decay via Majorana neutrinos at the LHC. The CP asymmetry stems from the significant interference of contributions from two different Majorana neutrinos and can be appreciable when the two neutrino masses are nearly-degenerate. It is found that in the Majorana neutrino mass range of 10 GeV < mn < 80 GeV, the CP asymmetry is independent of the Majorana neutrino mass at the LHC. Any possible new observation of CP violation will be the clear evidence of new physics beyond the standard model.

hep-ph↗

arXiv2021

Precise evaluation of $h\to c\bar{c}$ and axion-like particle production

We study the decay of the SM Higgs boson to a massive charm quark pair at the next-to-next-to-leading order QCD and next-to-leading order electroweak. At the second order of QCD coupling, we consider the exact calculation of flavour-singlet contributions where the Higgs boson couples to the internal top and bottom quark. Helpful information on the running mass effects related to Yukawa coupling may be obtained by analyzing this process. High precision production for $h\to c\bar{c}$ within the SM makes it possible to search for new physics that may induce relatively large interactions related to the charm quark. As an example, we evaluate the axion-like particle associate production with a charm quark pair in the Higgs decay and obtain some constraints for the corresponding parameters under some assumptions.

hep-ph↗

arXiv2018

Higgs production in association with bottom quark pair at LHC

The direct observation of the Yukawa interaction related to Standard Model Higgs and the bottom quark is obtained from the $h\to b\bar{b}$ process recently. The b-tagging becomes an important tool to search for new heavy resonance production at LHC. We use the b-tagging method to investigate the neutral Higgs production in association with a bottom quark pair, and perform the detector simulation for the signal process with the Higgs decaying into $b\bar{b}$ or $τ^+τ^-$ together with the dominant backgrounds. Our results show that $b\bar{b}b\bar{b}$ and $b\bar{b}τ^+τ^-$ processes will play an important role to search for the exotic heavy Higgs production at LHC and future hadron colliders.

hep-ph↗

arXiv2015

Associated Production of Higgs Boson and $t\bar t$ at LHC

One of the future goals of the LHC is to precisely measure the properties of Higgs boson. The associated production of Higgs boson and the top quark pair is a promising process to investigate the related Yukawa interaction and the properties of Higgs. Compared with the pure scalar sector in the Standard Model, the Higgs sector contains both scalar and pseudoscalar in many new physics models, which makes the $t\bar t H$ interaction more complex and provides a variety of phenomena. To investigate the $t\bar t H$ interaction and the properties of Higgs, we study the top quark spin correlation observables at the LHC.

hep-ph↗