arXiv subjects

Feng Feng

Publications and source records attributed to Feng Feng.

At least 37 records · Page 2Linked to original sources

arXiv2023

Optimized ${\cal O}(α_s^2)$ correction to exclusive double $J/ψ$ production at $B$ factories

The failure of observing the $e^+ e^- \to J/ψ+J/ψ$ events at $B$ factories to date is often attributed to the significant negative order-$α_s$ correction. In this work we compute the ${\cal O}(α^2_s)$ correction to this process for the first time. The magnitude of the next-to-next-to-leading order (NNLO) perturbative correction is substantially negative so that the standard NRQCD prediction would suffer from an unphysical, negative cross section. This dilemma may be traced in the fact that the bulk contribution of the fixed-order radiative corrections stems from the perturbative corrections to the $J/ψ$ decay constant. We thus implement an improved NRQCD factorization framework, by decomposing the amplitude into the photon-fragmentation piece and the non-fragmentation piece. With the measured $J/ψ$ decay constant as input, which amounts to resumming a specific class of radiative and relativistic corrections to all orders, the fragmentation-induced production rate can be predicted accurately and serves a benchmark prediction. The non-fragmentation type of the amplitude is then computed through NNLO in $α_s$ and at lowest order in velocity. Both the ${\cal O}(α_s)$ and ${\cal O}(α^2_s)$ corrections in the interference term become positive and exhibit a decent convergence behavior. Our finest prediction is $σ(e^+ e^- \to J/ψ+J/ψ)= 2.13^{+0.30}_{-0.06}$ fb at $\sqrt{s}=10.58$ GeV. With the projected integrated luminosity of 50 ${\rm ab}^{-1}$, the prospect to observe this exclusive process at \texttt{Belle} 2 experiment appears to be bright.

hep-ph↗

arXiv2023

Inclusive production of fully-charmed tetraquarks at LHC

The $X(6900)$ resonance, originally discovered by the \texttt{LHCb} collaboration and later confirmed by both \texttt{ATLAS} and \texttt{CMS} experiments, has sparked broad interests in the fully-charmed tetraquark states. Relative to the mass spectra and decay properties of fully-heavy tetraquarks, our knowledge on their production mechanism is still rather limited. In this work we investigate the inclusive production of fully-charmed $S$-wave tetraquarks at \texttt{LHC} within the nonrelativistic QCD (NRQCD) factorization framework. The partonic cross sections are computed at lowest order in $α_s$ and velocity, while the long-distance NRQCD matrix elements are estimated from phenomenological potential models. We predict the differential $p_T$ spectra of various fully-charmed $S$-wave tetraquarks at the \texttt{LHC}, and compare with the results predicted from the fragmentation mechanism at large $p_T$ end.

hep-ph↗

arXiv2022

Next-to-next-to-leading-order QCD corrections to $e^+e^-\to J/ψ+η_c$ at $B$ factories

Within the nonrelativistic QCD (NRQCD) factorization framework, we compute the long-awaited ${\mathcal O}(α_s^2)$ correction for the exclusive double charmonium production process at $B$ factories, {\it i.e.}, $e^+e^-\to J/ψ+η_c$ at $\sqrt{s}=10.58$ GeV. For the first time, we confirm that NRQCD factorization does hold at next-to-next-to-leading-order (NNLO) for exclusive double charmonium production. It is found that including the NNLO QCD correction considerably reduces the renormalization scale dependence, and also implies the reasonable perturbative convergence behavior for this process. Our state-of-the-art prediction is consistent with the BaBar measurement within errors.

hep-ph↗

arXiv2022

Three-loop QCD corrections to the decay constant of $B_c$

Within the framework of nonrelativistic QCD (NRQCD) factorization, we compute the three-loop QCD corrections to the decay constant of $B_c$. We reconstruct the analytical expressions for the three-loop renormalization constant and the corresponding anomalous dimension affiliated with the pseudoscalar current composed of two different heavy flavors in NRQCD, which are functions of the ratio between the charm and bottom quark masses. Meanwhile, the short-distance coefficient is obtained with very high numerical accuracy. The three-loop QCD correction turns out to be overwhelmingly large. The phenomenological implication of this new piece of radiative corrections for the $B_c$ leptonic decay is also addressed.

hep-ph↗

arXiv2022

Complete three-loop QCD corrections to leptonic width of vector quarkonium

Within the nonrelativistic QCD (NRQCD) factorization framework, we compute the order-$α_s^3$ perturbative corrections to the leptonic decay of the $Υ$ and $J/ψ$ with high numerical accuracy, at the lowest order in velocity expansion. We confirm the existing three-loop results in literature. Furthermore, we explicitly consider the complex-valued light-by-light (singlet) contributions. We for the first time also consider the finite charm quark mass effect for $Υ$ leptonic decay, and obtain a new piece of 3-loop contribution to the anomalous dimension related to the composite NRQCD bilinear of vector current that arises from the nonzero charm quark mass. Based on the complete three-loop NRQCD short-distance coefficients, we also present a comprehensive phenomenological analysis for $Υ(J/ψ)$ leptonic width.

hep-ph↗

arXiv2021

Gluon fragmentation into $B_c^{(*)}$ in NRQCD factorization

The universal fragmentation functions of gluon into the flavored quarkonia $B_c$ and (polarized) $B_c^*$ are computed within NRQCD factorization framework, at the lowest order in velocity expansion and strong coupling constant. It is mandatory to invoke the DGLAP renormalization program to render the NRQCD short-distance coefficients UV finite in a point-wise manner. The calculation is facilitated with the sector decomposition method, with the final results presented with high numerical accuracy. This knowledge is useful to enrich our understanding toward the large-$p_T$ behavior of $B_c^{(*)}$ production at LHC experiment.

hep-ph↗

arXiv2021

Next-to-leading-order QCD corrections to a vector bottomonium radiative decay into a charmonium

Within the framework of nonrelativistic QCD (NRQCD) factorization, we calculate the next-to-leading-order (NLO) perturbative corrections to the radiative decay $Υ\to η_c(χ_{cJ})+γ$. Both the helicity amplitudes and the helicity decay widths are obtained. It is the first computation for the processes involving both bottomonium and charmonium at two-loop accuracy. By employing the Cheng-Wu theorem, we are able to convert most of complex-valued master integrals (MIs) into real-valued MIs, which makes the numerical integration much efficient. Our results indicate the $\mathcal{O}(α_s)$ corrections are moderate for $η_c$ and $χ_{c2}$ production, and are quite marginal for $χ_{c0}$ and $χ_{c1}$ production. It is impressive to note the NLO corrections considerably reduce the renormalization scale dependence in both the decay widths and the branching fractions for $χ_{cJ}$, and slightly improve that for $η_c$. With the NRQCD matrix elements evaluated via the Buchmüller-Tye potential model, we find the decay width for $η_c$ production is one-order-of-magnitude larger than $χ_{cJ}$ production, which may provide a good opportunity to search for $Υ\to η_c+γ$ in experiment. In addition, the decay width for $χ_{c1}$ production is several times larger than those for $χ_{c0,2}$. Finally, we find the NLO NRQCD prediction for the branching fraction of $Υ\to χ_{c1}+γ$ is only half of the lower bound of the experimental data measured recently by {\tt Belle}. Moreover, there exists serious contradiction between theory and experiment for $Υ\to η_c+γ$. The discrepancies between theory and experiment deserve further research efforts.

hep-ph↗

arXiv2021

Evaluation of the effect of edge cracks on critical current degradation in REBCO tapes under tensile stress

The slitting process used for fabrication of REBa2Cu3Ox (REBCO, RE=Rare earth) tapes of required width will greatly improve production efficiency and reduce production costs. However, edge cracks induced by the slitting process of wide REBCO tapes may cause the premature degradation under a extremely high hoop (tensile) stress in high-field magnets. It is necessary to evaluate the edge cracks of REBCO tapes on the critical current (Ic) degradation. This work aims to evaluate the effect of edge cracks on the Ic performance under tensile stress. Ic degradation under artificial cracks was measured to validate the applicability of linear elastic fracture mechanics for the REBCO film. Linear elastic fracture mechanics was used to get the mixed stress intensity factor of multiple edge oblique cracks. A model considering edge crack properties angle \b{eta}, spacing d, and length a is constructed to evaluate the critical load and critical cracks properties. When the stress intensity factor at the crack tip is less than K_{\rm Ic}=2.3$ $\mathrm{MPa\sqrt{m}}, edge cracks remain stable and do not propagate. Two kinds of REBCO tapes fabricated by different companies are evaluated, and cracks of these tapes will not cause premature degradation. This model could be used to evaluate the operation range of REBCO tapes and improve the manufacturing process.

cond-mat.supr-con↗

arXiv2021

Next-to-leading-order QCD corrections to heavy quark fragmentation into ${}^1S^{(1,8)}_0$ quarkonia

Within NRQCD factorization framework, in this work we compute, at the lowest order in velocity expansion, the next-to-leading-order (NLO) perturbative corrections to the short-distance coefficients associated with heavy quark fragmentation into the ${}^1S_0^{(1,8)}$ components of a heavy quarkonium. Starting from the Collins and Soper's operator definition of the quark fragmentation function, we apply the sector decomposition method to facilitate the numerical manipulation. It is found that the NLO QCD corrections have a significant impact.

hep-ph↗

arXiv2021

Inclusive production of fully-charmed ${\bm 1}^{\bm{+}\bm{-}}$ tetraquark at $\bm B$ factory

Inspired by the recent discovery of the $X(6900)$ meson at {\tt LHCb} experiment, we investigate the inclusive production rate of the $C$-odd fully-charmed tetraquarks associated with light hadrons at the $B$ factory within the nonrelativistic QCD (NRQCD) factorization framework. The short-distance coefficient is computed at lowest order in velocity and $α_s$. Employing the diquark-antidiquark model to roughly estimate the long-distance NRQCD matrix elements, we predict the rate for inclusive production of the $1^{+-}$ $T_{4c}$ state and discuss the observation prospects at {\tt Belle 2} experiment.

hep-ph↗

arXiv2021

HepLib: A C++ Library for High Energy Physics

HepLib is a C++ Library for computations in High Energy Physics, it works on top of GiNaC, a well-established C++ library used to perform symbolic computations. HepLib combines serval well-known packages to get high efficiency, including Qgraf to generate Feynman aptitudes, FORM to perform Dirac/Color matrix related computations, and FIRE or KIRA for integration-by-parts (IBP) reduction. Another core feature of HepLib lies in the numerical evaluation of master integrals using sector decomposition, which is a general method widely used in high-order numerical computation and has been implemented in many public packages in many different languages, and we present another implementation in the language of C++ with many new features. We use GiNaC to handle the symbolic operations, and export the corresponding integrand into an optimized C++ code, that will be compiled internally and linked dynamically, a customizable numerical integrator is selected to perform the numerical integration, while the integrand can be evaluated in different float precisions, including the arbitrary precision supported by MPFR.

hep-ph↗

arXiv2020

Multiplexing-oriented plasmon-MoS2 hybrid metasurfaces driven by nonlinear quasi bound states in the continuum

Rapid progress in nonlinear plasmonic metasurfaces enabled many novel optical characteristics for metasurfaces, with potential applications in frequency metrology, timing characterization and quantum information. However, the spectrum of nonlinear optical response was typically based upon the linear optical resonance. In this work, a wavelength-multiplexed nonlinear plasmon-MoS2 hybrid metasurface with suppression phenomenon was proposed, where multiple nonlinear signals could to be simultaneously processed and optionally tuned. A clear physical picture to depict the nonlinear plasmonic bound states in the continuum (BICs) was presented, from the perspective of both classical and quantum approaches. Particularly, beyond the ordinary plasmon-polariton effect, we numerically demonstrated a giant BIC-inspired second-order nonlinear susceptibility $10^{-5}$~$m/V$ of MoS2 in the infrared band. The novelty in our study lies in the presence of a quantum oscillator that can be adopted to both suppress and enhance the nonlinear quasi BICs. This selectable nonlinear BIC-based suppression and enhancement effect can optionally block undesired modes, resulting in narrower linewidth as well as smaller quantum decay rates, which is also promising in slow-light-associated technologies.

physics.optics↗

arXiv2020

Exclusive radiative production of fully-charmed tetraquarks at $B$ Factory

We apply the newly developed NRQCD factorization formula to analyze the exclusive production of the fully-charmed tetraquark $T_{4c}$ plus a hard photon at $B$ factory. For simplicity, in this work we have concentrated on the associated production of the $0^{++}$ and $2^{++}$ tetraquarks with a photon. With some rough estimates about the size of the unknown nonperturbative NRQCD matrix elements, we predict the production rates of these types of exclusive channels at $\sqrt{s}=10.6$ GeV and also assess their observation prospect at {\tt Belle 2} experiment.

hep-ph↗

arXiv2020

Next-to-Next-to-Leading-Order Radiative Corrections to $e^+e^-\toχ_{cJ}+γ$ at $B$ factory

Within the nonrelativistic QCD (NRQCD) factorization framework, we have computed the ${\mathcal O}(α_s^2)$ corrections to the exclusive production of $P$-wave spin-triplet charmonia $χ_{cJ}(J=0,1,2)$ accompanied by a hard photon at $B$ factories. For the first time, we have explicitly verified the validity of NRQCD factorization for exclusive $P$-wave quarkonium production at two-loop order. Unlike the $χ_{cJ}$ electromagnetic decay processes, the $\mathcal{O}(α_s^2)$ corrections are found to be smaller than the $\mathcal{O}(α_s)$ corrections in all three channels $e^+e^-\to χ_{c0,1,2}+γ$. In particular, the ${\mathcal O}(α_s^2)$ corrections appear moderate for $χ_{c1}$ case, and insignificant for $χ_{c0}$. In addition, the next-to-next-to-leading order (NNLO) predictions for the production rates of $χ_{c0,1}+γ$ are insensitive to the renormalization and factorization scales. All of these features may indicate that perturbative expansion in these two channels exhibits a decent convergence behavior. By contrast, both the ${\mathcal O}(α_s)$ and ${\mathcal O}(α_s^2)$ corrections to the $χ_{c2}+γ$ production cross section are sizable, which even reduces the Born order cross section by one order of magnitude after including the NNLO perturbative correction. Taking the values of the long-distance NRQCD matrix elements from nonrelativistic potential model, our prediction to $χ_{c1}+γ$ production rate is consistent with the recent {\tt Belle} measurement. The NNLO predictions for the $χ_{c0,2}+γ$ production rates are much smaller than that for $χ_{c1}+γ$, which seems to naturally explain why the $e^+e^-\to χ_{c0,2}+γ$ channels have escaped experimental detection to date.

hep-ph↗

arXiv2020

${\cal O}(α_sv^2)$ corrections to hadronic decay of vector quarkonia

Within the nonrelativistic QCD (NRQCD) factorization framework, we compute the ${\mathcal O}(α_s v^2)$ corrections to the hadronic decay rate of vector quarkonia, exemplified by $J/ψ$ and $Υ$. Setting both the renormalization and NRQCD factorization scales to be $m_Q$, we obtain $Γ(J/ψ\to {\rm LH})= 0.0716\frac{α_s^3}{m_c^2} \langle \mathcal{O}_1({}^3S_1)\rangle_{J/ψ} [1-1.19α_s+(-5.32+3.03α_s)\langle v^2\rangle_{J/ψ}]$ and $Γ(Υ\to {\rm LH})= 0.0716\frac{α_s^3}{m_b^2}\langle\mathcal{O}_1({}^3S_1)\rangle_Υ[1-1.56α_s+(-5.32+4.61α_s)\langle v^2\rangle_Υ]$. We confirm the previous calculation of $\mathcal{O}(α_s)$ corrections on a diagram-by-diagram basis, with the accuracy significantly improved. For $J/ψ$ hadronic decay, we find that the ${\mathcal O}(α_sv^2)$ corrections are moderate and positive, nevertheless unable to counterbalance the huge negative corrections. On the other hand, the effect of ${\mathcal O}(α_sv^2)$ corrections for $Υ(nS)$ is sensitive to the $\mathcal{O}(v^2)$ NRQCD matrix elements. With the appropriate choice of the NRQCD matrix elements, our theoretical predictions for the decay rates may be consistent with the experimental data for $Υ(1S,2S)\to {\rm LH}$. As a byproduct, we also present the theoretical predictions for the branching ratio of $J/ψ(Υ)\to 3γ$ accurate up to $\mathcal{O}(α_s v^2)$.

hep-ph↗

arXiv2020

Fragmentation production of fully-charmed tetraquarks at LHC

The $X(6900)$ resonance, very recently discovered in the double-$J/ψ$ channel at LHCb experiment, has spurred intensive interest in unravelling the nature of the fully charmed tetraquark state. The aim of this paper is to present a model-independent theoretical framework to study the inclusive production of this novel species of exotic hadrons, the resonances composed of four heavy quark (commonly referred to as $T_{4c}$), at large $p_T$ in hadron collision experiments. Appealing to asymptotic freedom and the fact $m_c\gg Λ_{\rm QCD}$, we propose that the nonpertubative yet universal gluon-to-$T_{4c}$ fragmentation function, can be decomposed into the product of the perturbatively calculable short-distance coefficient and the long-distance NRQCD matrix elements. We compute the short-distance coefficient at lowest-order in $α_s$ and velocity expansion. Adopting the diquark ansatz to roughly estimate those not-yet-known NRQCD matrix elements, together with the standard QCD factorization theorem, we predict the differential production rates for the $T_{4c/4b}(0^{++})$ and $T_{4c/4b}(2^{++})$ at large $p_T$ in $pp$ collision, which eagerly awaits the confrontation with the future LHC experiments.

hep-ph↗

arXiv2020

Can rhythm be touched? An evaluation of rhythmic sketch performance with augmented multimodal feedback

Although it has been shown that augmented multimodal feedback has a facilitatory effect on motor performance for motor learning and music training, the functionality of haptic feedback combined with other modalities in rhythmic movement tasks has rarely been explored and analysed. In this paper, we evaluate the functionality of visual-haptic feedback in a rhythmic sketch task by comparing it with other multimodal conditions. Further, we examine the possibility of accessing the quality of task execution through kinematic analysis. Based on participants' speed profiles, we investigate the quality of motor control and movement smoothness under different feedback conditions. Results revealed better motor control ability with auditory feedback and improved movement smoothness with haptic feedback. Finally, we propose that haptic feedback can be integrated with other modal stimuli for different interaction purposes, and that kinematic analysis can be a complementary approach to gesture analysis as well as providing subjective evaluation of interaction performance.

cs.HC↗

arXiv2020

Concurrent Crossmodal Feedback Assists Target-searching: Displaying Distance Information Through Visual, Auditory and Haptic Modalities

Humans sense of distance depends on the integration of multi sensory cues. The incoming visual luminance, auditory pitch and tactile vibration could all contribute to the ability of distance judgement. This ability can be enhanced if the multimodal cues are associated in a congruent manner, a phenomenon has been referred to as Crossmodal correspondences. In the context of multi-sensory interaction, whether and how such correspondences influence information processing with continuous motor engagement, particularly for target searching activities, has rarely been investigated. This paper presents an experimental user study to address this question. We built a target-searching application based on a Table-top, displayed the unimodal and Crossmodal distance cues concurrently responding to peoples searching movement, measured task performance through kinematic evaluation. We find that the Crossmodal display an audio display lead to improved searching efficiency and accuracy. More interestingly, this improvement is confirmed by kinematic analysis, which also unveiled the underlying movement features that could account for this improvement. We discussed how these findings could shed lights on the design of assistive technology and of other multi sensory interaction.

cs.HC↗