arXiv subjects

Vindhyawasini Prasad

Publications and source records attributed to Vindhyawasini Prasad.

15 recordsLinked to original sources

arXiv2026

Recent CLFV searches at Belle and Belle II

Charged lepton flavor violation (CLFV) is forbidden in the Standard Model (SM) due to massless neutrinos and absence of right-handed neutrinos. The discovery of neutrino oscillations established that the neutrinos are massive and the lepton flavor is not an exact symmetry of nature. A minimal extension of the SM that incorporates right-handed neutrinos gives rise to CLFV through loop-level diagrams involving neutrinos. However, such processes are extremely rare, for instance, the branching fraction of $μ\to eγ$ is expected to be at the level of $10^{-54}$, far beyond the sensitivity of current collider experiments. In contrast, several new physics models predict CLFV decay rates within the sensitivity of current experiments, such as the Belle and Belle II experiments, which have collected the world's largest asymmetric $e^+e^-$ collision data near the $Υ(4S)$ resonance. The large data sample has utilized to explore the possibility of CLFV decays of $τ$ leptons, $B$ mesons, and bottomonium states. The report reviews some latest results on these CLFV decays at Belle and Belle II.

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arXiv2026

Polarized observables in $τ\to VV ν_τ$ decays

We study polarization observables in $τ^- \to V_1^- V_2^0 ν_τ$ decays for $(V_1^-, V_2^0)=(ρ^-, ρ^0), (ρ^-, ω), (K^{*-}, ρ^0), (K^{*-}, ω), (ρ^-, \bar{K}^{*0})$ using the helicity formalism within the generalized hidden local symmetry framework. The predicted branching fractions are comparable with those from the effective chiral model, but smaller than those from the angular momentum algebra model. Our results for the longitudinal polarization fractions $f_L$ indicate that nonnegligible corrections to the endpoint limit ($f_L = 1/3$), a consequence of Lorentz symmetry, are present at the scale of tau mass. Future measurements of $f_L$ at Belle II for $τ^- \to V_1^- V_2^0 ν_τ$ decays will provide crucial information on polarization patterns observed in nonleptonic charm decays.

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arXiv2026

Search for invisible decays of light mesons via $J/ψ\to VP$ $(V=ω/ϕ,P=η/η')$ decays at STCF

We present a preliminary feasibility study of searches for invisible decays of light mesons via $J/ψ\to VP$ $(V=ω/ϕ,P=η/η')$ using a traditional analytical method at the proposed Super $τ$-Charm facility (STCF) which is expected to accumulate $3.4\times10^{12}$ $J/ψ$ events per year, based on an inclusive Monte Carlo sample of $1.3 \times 10^{9}$ $J/ψ$ events. The upper limits on the invisible decay branching fractions at the 90\% confidence level are set as $\mathcal{B}(ω\to invisible) < 3.7 \times 10^{-7}$, $\mathcal{B}(ϕ\to invisible) < 8.9 \times 10^{-7}$, $\mathcal{B}(η\to invisible) < 1.8 \times 10^{-7}$ and $\mathcal{B}(η' \to invisible) < 4.1 \times 10^{-7}$, respectively, using a projected toy data corresponding to the expected STCF statistics. By using the machine learning technique such as Deep Learning, the upper limit may be further improved to approach theoretical predictions for light dark matter.

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arXiv2025

New Physics Searches at BESIII

This report highlights the recent BESIII results related to the new physics searches motivated by the shortcomings of Standard Model, such as the exclusion of dark matter (DM). DM has so far been inferred only through astrophysical observations and accounts for a large fraction of matter density of the universe. DM may couple to SM particles via various portals. These portals give rise to several possible new particles beyond the SM, such as light Higgs bosons, dark photons, axion-like particles, or spin-1/2 fermions. Furthermore, the origin of DM and the observed asymmetry between visible matter and antimatter may be connected through the introduction of a dark baryon. The signature of these new physics particles could be accessible by the BESIII if their masses lie in the few-GeV range.

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arXiv2025

Dark sector at BESIII

Dark matter (DM) plays a crucial role in explaining the observed astrophysical anomalies, galaxy rotation curves, and other fundamental characteristics of the Universe. Many extensions of the Standard Model (SM), such as the dark hidden-sector model, provide an attractive framework in which DM can couple to SM particles via various portals. These portals give rise to several possible new particles beyond the SM, such as light Higgs bosons, dark photons, and axion-like particles. Furthermore, the origin of DM and the observed asymmetry between visible matter and antimatter may be connected through the introduction of a dark baryon. If the masses of these hypothetical particles lie in the few-GeV range, they can be explored at high-intensity $e^+e^-$ collider experiments, such as the BESIII experiment. This report presents a review of recent BESIII results related to searches for dark-sector particles.

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arXiv2025

Dark matter searches at BESIII

Dark matter (DM) is a new type of invisible matter introduced to explain various features of recent astrophysical observations, including galaxy rotation curves and other fundamental characteristics of our universe. DM may couple to ordinary matter via portals, which open up possibilities for new particles, such as axion-like particle, light Higgs boson, dark photon, and spin-1/2 fermions. If the masses of these particles lie in the MeV to GeV range, they can be explored by high-intensity electron-positron collider experiments, such as the BESIII experiment. BESIII has accumulated a huge amount of datasets at several energy points, including the $J/ψ$, $ψ(3686)$, and $ψ(3770)$ resonances. BESIII has recently explored the possibility for axion-like particle and light Higgs boson through radiative $J/ψ$ decays, dark photon via the initial-state radiation process, and a massless dark photon in $Λ_c$ decays. This report highlights the latest results from the BESIII experiment on these topics.

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arXiv2024

Highlights of recent BESIII results

This report highlights the recent BESIII results related to the measurement of the $R$ value, radiative decays of $J/ψ$ and the polarization of $D^0 \to ωϕ$ decay. BESIII, a symmetric electron-positron collider experiment, has collected a large data sample at several energy points in the tau-charm region, including the $J/ψ$ and $ψ(3770)$ resonances. Based on the data samples collected at 14 center-of-mass energy ($\sqrt{s}$) points between 2.2323 and 3.671 GeV, BESIII has achieved a measurement of the $R$ value with an accuracy down to the level of $2.6\%$ for $\sqrt{s} < 3.1$ GeV and $3.0\%$ for $\sqrt{s} > 3.1$ GeV. BESIII has also observed the $X(2600)$ resonance in radiative $J/ψ$ decay and the polarization of $D^0 \to ωϕ$ for the first time. The polarization of $D^0 \to ωϕ$ saturates with completely transverse polarization, which is inconsistent with the existing theoretical models. These results are useful in testing the predictions of the Standard Model.

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arXiv2023

Dark sector and Axion-like particle search at BESIII

Dark matter (DM) refers to a new type of matter that may explain observed rotation curves of galaxies and the composite structure of the Universe. It may couple to the Standard Model particles via portals, which include the possibility of axion-like particle, light Higgs boson, dark photon and spin-1/2 fermions. The axion-like particle and light Higgs boson can be accessible via radiative decays of $J/ψ$ while the dark photon via initial-state radiation process using the data of high-intensity $e^+e^-$ collider experiments, such as the BESIII experiment. DM may be depicted as baryonic matter in an invisible final state. The presence of a massless dark photon, predicted by the spontaneous broken of Abelian group $U(1)_D$, may enhance the branching fractions of rare flavor changing neutral current decay processes. BESIII experiment has recently explored the possibility of these DM scenarios using the data samples collected at several energy points, including $J/ψ$ and $ψ(3686)$ resonances. This report summarizes the recent results of the BESIII experiment related to the dark-sector and Axion-like particles.

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arXiv2019

Dark matter/new physics searches at BESIII

Many new physics models beyond the Standard Model, motivated by the recent astrophysical anomalies, include the possibility of several new types of light weak-interacting particles. Typical models, such as Next-to-Minimal Supersymmetric Standard Model and Hidden Dark-sector Model, predict the light Higgs and dark bosons, respectively. The masses of these particles are expected to be a few GeV and thus making them accessible at BESIII. BESIII has recently explored the possibility of light Higgs and dark bosons in several decay modes using the data-sets collected at $J/ψ$, $ψ(3686)$ and $ψ(3770)$ resonances. The $J/ψ$ data have further utilized to search for invisible decays of light vector ($V=ω, ϕ$) and pseudo-scalar ($P=η, η'$) mesons via $J/ψ\to VP$ decays. This report summarizes the recent results of the BESIII experiment on these new physics topics.

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arXiv2019

Light Hadron Spectroscopy and Decay at BESIII

Light hadron spectroscopy plays an important role in understanding the decay dynamics of unconventional hadronic states, such as strangeonium and glueballs. BESIII provides an ideal avenue to search for these exotic states thanks to a huge amount of data recorded at various energy points in the tau-charm mass region including J/psi resonance. This report summarizes recent results of the BESIII experiment related to the glueballs and strangeonium-like states.

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arXiv2016

Study of BESIII electromagnetic calorimeter performance with radiative lepton pair events

We study the photon detection efficiency and position resolution of the electromagnetic calorimeter (EMC) of the BESIII detector. The control samples of the initial-state-radiation (ISR) process of $e^+e^-\rightarrow γμ^+μ^-$ at $J/ψ$ and $ψ(3770)$ resonances are used for the calibration of the photon cluster shapes and photon detection efficiency study. The photon detection efficiency is defined as the fraction of predicted photon, determined by performing a kinematic fit with the four momenta of two charged tracks only, matched with the actual photons in the EMC. The spatial resolution of the EMC is studied in polar ($θ$) and azimuthal ($ϕ$) angle directions in a cylindrical coordinate system centered at the interaction point, with z-axis along the beam direction.

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arXiv2015

Search for low-mass Higgs and dark photons at BESIII

Many extensions of the Standard Model introduce a new type of weak-interacting degrees of freedom. These models are motivated by the results of recent experimental anomalies. Typical models, such as Next-to-Minimal Supersymmetric Standard Model and Light Hidden Dark-sector Model, introduce the possibilities of low-mass Higgs and dark bosons. The masses of such particles are expected to be few GeV and thus making them accessible at BESIII experiment, an $e^+e^-$ collider experiment running at tau-charm region. This report summarizes the recent results of low-mass Higgs and dark bosons searches at BESIII.

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arXiv2015

XYZ radiative transitions at BESIII

Many unexpected charmonium-like states have recently been observed above the $D\overline{D}$ threshold, which features can't be explained by the conventional quark models. These states are known as XYZ mesons. The study of the radiative transition among these states can provide the important features of XYZ states. This study has recently been performed by the BESIII using the large data samples collected at different center-of-mass energies above 3.8 GeV. This report summarizes the recent results of XYZ radiative transitions at BESIII.

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arXiv2015

Study of photon detection efficiency and position resolution of BESIII electromagnetic calorimeter

We study the photon detection efficiency and position resolution of the electromagnetic calorimeter (EMC) of the BESIII experiment. The control sample of the initial-state-radiation (ISR) process of $e^+e^-\rightarrow γμ^+μ^-$ is used at $J/ψ$ and $ψ(3770)$ resonances for the EMC calibration and photon detection efficiency study. Photon detection efficiency is defined as the predicted photon, obtained by performing a kinematic fit with two muon tracks, matched with real photons in the EMC. The spatial resolution of the EMC is defined as the separation in polar ($θ$) and azimuthal ($ϕ$) angles between charged track and associated cluster centroid on the front face of the EMC crystals.

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arXiv2013

Search for di-muon decays of a light scalar Higgs boson in radiative Y(1S) decays

We search for di-muon decays of a low-mass Higgs boson ($A^0$) in the fully reconstructed decay chain of $Υ(2S,3S) \to \pipiΥ(1S)$, $Υ(1S) \to \g A^0$, $A^0 \to \mumu$. The $A^0$ is predicted by several extensions of the Standard Model (SM), including the Next-to-Minimal Supersymmetric Standard Model (NMSSM). NMSSM introduces a \CP-odd light Higgs boson whose mass could be less than 10 \gevcc. The data samples used in this analysis contain $92.8 \times 10^6$ $Υ(2S)$ and $116.8 \times 10^6$ $Υ(3S)$ events collected by the \babar\ detector. The $Υ(1S)$ sample is selected by tagging the pion pair in the $Υ(2S, 3S) \to π^+π^-Υ(1S)$ transitions. We find no evidence for $A^0$ production and set 90% confidence level (C.L.) upper limits on the product branching fraction $\mathcal{B}(Υ(1S) \to \g A^0) \times \mathcal{B}(A^0 \to \mumu)$ in the range of $(0.28 - 9.7)\times 10^{-6}$ for $0.212 \le m_{A^0} \le 9.20$ \gevcc. We also combine our results with previous \babar\ results of $Υ(2S,3S) \to \g A^0$, $A^0 \to \mumu$ to set limits on the effective coupling ($f_Υ$) of the \b-quark to the $A^0$, $f_Υ^2 \times \mathcal{B}(A^0 \to \mumu)$, at the level of $(0.29 - 40)\times 10^{-6}$ for $0.212 \le m_{A^0} \le 9.2$ GeV/$c^2$.

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