arXiv subjects
Publications and source records attributed to A. Upadhyay.
In this paper, we revise some results on rigidity and vanishing properties obtained by \textit{Cuong et.al} in \cite{CDS24} on $n$-dimensional totally real minimal submanifolds $M$ immersed in complex space forms $\widetilde{M}^n(c)$, for $c\leq0$. We extend the range of $p$ in their paper.
A statistical framework in conjugation with the principle of detailed balance is employed to examine the low-energy properties i.e. charge radii and quadrupole moment of J$^P$=$\frac{1}{2}^+$ octet and J$^P$=$\frac{3}{2}^+$ decuplet baryon. The statistical approach assumes the expansion of baryonic system in terms of quark-gluon Fock states. We systematically apply operator formalism along with the statistical approach to study the charge radii and quadrupole moment of baryons. Based on the probabilities of all possible Fock states in spin, flavor and color space, the importance of sea with quarks and gluons is studied. The individual contribution of the constituent quarks and sea which contains terms of scalar, vector and tensor is explored. Due to large mass difference between strange and non-strange content, the SU(3) breaking effect are also investigated. The extent to which strange quark-antiquark pair is considered in sea is constrained by the mass of hadrons, the free energy of gluons in conformity with experimental indications. We focus on the individual contribution of strange and non-strange sea (g, $\langle u\bar u\rangle$, $\langle d\bar d\rangle$ and $\langle s\bar s\rangle$) accomodability in the respective hadrons for their charge radii and quadrupole moment. The present work has been compared with various theoretical approaches and some known experimental observations. Our computed results may provide important information for upcoming experimental findings.
We have employed HQET to determine the masses of radially excited ($n=2$) S-wave charm and bottom baryons. The HQET Lagrangian containing the non-perturbative parameters is shown with heavy baryon fields. The non-perturbative parameters, couplings, and decay widths are also studied for the S-wave singly heavy baryons. The HQET parameters $\overlineΛ$, $λ_1$ and $λ_2$ are calculated for the ground state ($n=1$) using the masses of S-wave baryons. The mass term ratios of $n=1$ and $n=2$ mesons and baryons containing parameters $\overlineΛ$ and $λ_1$ are studied by varying the bottom quark mass. This analysis shows that heavy quark behaves the same inside mesons and baryons in both 1S and 2S states. The HQET symmetry of $\overlineΛ$ is used to find the parameters and masses for $n=2$ S-wave baryons. The variation of mass of 2S baryons with the non-perturbative parameters $λ_1$ and $λ_2$ is discussed. The Regge trajectories are also plotted in the $(n,M^2)$ plane using masses of $n=1$ and 2 charm and bottom baryons. The Regge trajectories are parallel and equidistant lines in the $(n,M^2)$ plane. We have also studied the strong decays of charm and bottom baryons for both $n=1$ and $n=2$ states. We have estimated the coupling constants $g_1=0.913^{+0.010}_{-0.017}$ and $g_2=0.559^{+0.006}_{-0.010}$ for $n=1$, and $\frac{\widetilde{g}_1}{\widetilde{g}_2}=1.52$ for $n=2$. We have also shown the semi-electronic decays rates of charm baryons in the spectator heavy quark approximation for $1S\rightarrow 1S$, $2S\rightarrow 1S$ and $2S\rightarrow 2S$ transitions. The decay rates for $1S\rightarrow 1S$ transitions are of same order as $2S\rightarrow 1S$ transitions. This analysis gives a good agreement with available theoretical and experimental data.
We have employed HQET to give the spin-parity quantum numbers for recently observed bottom strange states $B_{sJ}(6063)$ and $B_{sJ}(6114)$ by LHCb collaborations. By exploring flavour independent parameters $ Δ_{F}^{(c)} =Δ_{F}^{(b)}$ and $ λ_{F}^{(c)} = λ_{F}^{(b)}$, we calculated masses of experimentally missing bottom strange meson states $2S, 1P, 1D$. We have also analyzed these bottom strange masses by taking ${1/m_Q}$ corrections which lead modifications of parameter terms as $ Δ_{F}^{(b)} =Δ_{F}^{(c)} + δΔ_F$ and $ λ_{F}^{(b)} = λ_{F}^{(c)}δλ_F$. Further, we have analyzed their two-body decays, couplings, and branching ratios via the emission of light pseudoscalar mesons. Based on predicted masses and decay widths, we tentatively identified the states $B_{sJ}(6063)$ as $2^3S_1$ and $B_{sJ}(6114)$ as $1^3D_1$. Our predictions provide crucial information for future experimental studies.
We have combined two low-threshold detector technologies to develop a large-mass, low-threshold detector system that simultaneously measures the athermal phonons in a sapphire detector while an adjacent silicon high-voltage detector detects the scintillation light from the sapphire detector. This detector system could provide event-by-event discrimination between electron and nuclear events due to the difference in their scintillation light yield. While such systems with simultaneous phonon and light detection have been demonstrated earlier with smaller detectors, our system is designed to provide a large detector mass with high amplification for the limited scintillation light. Future work will focus on at least an order of magnitude improvement in the light collection efficiency by having a highly reflective detector housing and custom phonon mask design to maximize light collection by the silicon high-voltage detector.
The transformation between the metallic ($β$) and semi-conducting ($α$) allotropes of tin is still not well understood. The phase transition temperature stated in the literature, 286.2 K, seems to be inconsistent with recent calorimetric measurements. In this paper, this intriguing aspect has been explored in Sn and Sn-Cu (alloyed 0.5% Cu by weight) using temperature resolved synchrotron x-ray diffraction measurements performed at the Indus-2 facility. Additionally, the $α\rightleftharpoons β$ Sn transition has been recorded using in-situ heating/cooling experiments in a scanning electron microscope. Based on these measurements, a protocol has been suggested to reduce the formation of $α$-Sn in potentially susceptible systems. This will be useful in experiments like TIN.TIN (The INdia-based TIN detector), which proposes to employ ~100 - 1000 kg of superconducting tin-based detectors to search for neutrinoless double beta decay in the isotope $^{124}$Sn.
An experimental study of laser driven electron acceleration in N2 and N2-He mixed gas-jet target using laser pulses of duration ~60-70 fs is presented. Generation of relativistic electron beam with quasi-thermal spectra was observed at a threshold density of ~1.6x1018 cm-3 in case of pure N2, and the threshold density was found to increase with increasing doping concentration of He. At an optimum fraction of 50% of He in N2, generation of quasi-monoenergetic electron beams was observed at a comparatively higher threshold density of ~2x1018 cm-3, with an average peak energy of ~168 MeV, average energy spread of ~21%, and average total beam charge of ~220 pC. Electron acceleration could be attributed to the direct laser acceleration as well as the hybrid mechanism. Observation of an optimum fraction of He in N2 (in turn threshold plasma density) for comparatively better quality electron beam generation could be understood in terms of the plasma density dependent variation in the dephasing rate of electrons with respect to transverse oscillating laser field. Results are also supported by the 2D PIC simulations performed using code EPOCH.
An experimental study on 55fs laser driven plasma accelerator using mixed gas-jet target with varying plasma density is used to identify the role of different acceleration mechanisms, viz. Direct Laser Acceleration (DLA) and wakefield. At lower electron density electron acceleration could be attributed mainly to DLA with ionization induced injection. With increase in density, increasing role of wakefield was observed leading to hybrid regime, and at densities higher than self-injection threshold, observed experimentally for He target contribution of DLA and wakefield was found to be comparable. Dominant DLA mechanism was also observed in case of pure nitrogen target. 2D PIC simulations performed using the EPOCH code corroborate the above scenario, and also showed generation of surface waves, considered as a potential mechanism of pre-acceleration to DLA.
In this article, we study the two body strong decays with the emission of light pseudo-scalar mesons $(π, η, K)$ for higher excited bottom states with in the framework of HQET. Inspired from the recent observation of bottom meson $B_{J}(5840)$ by LHCb collaboration \cite{9}, we classify the six possible $J^{P}$'s for this state on the basis of the theoretically available masses. By analyzing the strong decay widths and the branching ratios for all these six cases of $B_{J}(5840)$, we justify one of them to be the most favorable assignment for it. We also examined the recently observed bottom state $B_{J}(5970)$ as 2S$1^{-}$ and states $B_{J}(5721)$ and $B_{2}^{*}(5747)$ with their strange partners $B_{s1}(5830)$ and $B_{2s}^{*}(5840)$ for their $J^{P}$'s as $1P_{3/2}1^{+}$ and $1P_{3/2}2^{+}$ respectively. The predicted coupling constants $g_{XH}$, $\widetilde{g}_{HH}$ and $g_{TH}$ helps in redeeming the strong decay width of experimentally missing bottom states $B(2 ^{1}S_{0})$, $B_{s}(2 ^{3}S_{1})$, $B_{s}(2 ^{1}S_{0})$, $B(1 ^{1}D_{2})$, $B_{s}(1 ^{3}D_{1})$ and $B_{s}(1 ^{1}D_{2})$. These predictions provide a crucial information for upcoming experimental studies.
In this paper, we analyzed the experimentally available radially excited charm mesons to predict the similar spectra for the n=2 bottom mesons. In the heavy quark effective theory, we explore the flavor independent parameters to calculate the masses for the experimentally unknown n=2 bottom mesons B(2S), B(2P), Bs(2S) and Bs(2P). We have also analyzed these bottom masses by applying the QCD and 1/mQ corrections to the lagrangian leading to the modification of flavor symmetry parameters as. Further strong decay widths are determined using these calculated masses to check the sensitivity of these corrections for these radially excited mesons. The calculated decay widths are in the form of strong coupling constant geHH, egSH and egTH. We concluded that these corrections are less sensitive for n=2 masses as compared to n=1 masses. Branching ratios and branching fractions of these states are calculated to have a deeper understanding of these states. These predicted values can be confronted with the future experimental data.
Using the effective Lagrangian approach, we examine the recently observed charm states $D^{*}_{J}(2460)$, $D_{J}(2560)$, $D_{J}(2740)$, $D_{J}(3000)$ and their spin partners $D^{*}_{J}(2680)$, $D^{*}_{J}(2760)$ and $D^{*}_{J}(3000)$ with $J^{P}$ states $1P_{\frac{3}{2}}2^{+}$, $2S_{\frac{1}{2}}0^{-}$, $1D_{\frac{5}{2}}2^{-}$, $2P_{\frac{1}{2}}1^{+}$ and $2S_{\frac{1}{2}}1^{-}$, $1D_{\frac{5}{2}}3^{-}$, $2P_{\frac{1}{2}}0^{+}$ respectively. We study their two body strong decays, coupling constants and branching ratios with the emission of light pseudo-scalar mesons $(π, η, K)$. We also analyze the newly observed charm state $D^{*}_{2}(3000)$ and suggest it to be either $1F(2^{+})$ or $2P(2^{+})$ state and justify one of them to be the most favorable assignment for $D^{*}_{2}(3000)$. We study the partial and the total decay width of unobserved states $D(1^{1}F_{3})$, $D_{s}(1 ^{1}F_{3})$ and $D_{s}(1 ^{1}F_{2})$ as the spin and the strange partners of the $D^{*}_{2}(3000)$ charmed meson. The branching ratios and the coupling constants $g_{TH}$, $\widetilde{g}_{HH}$, $g_{YH}$, $\widetilde{g}_{SH}$ and $g_{ZH}$ calculated in this work can be confronted with the future experimental data.
Generation of collimated, quasi-monoenergetic electron beams (peak energy ~17-22MeV, divergence ~10mrad, energy spread ~20%) by interaction of Ti:sapphire laser pulse of 200fs duration, focussed to an intensity of ~ 2.1x10^18 W/cm^2,with an under-dense (density~3.6x10^19 to ~1.1x10^20 cm-3) He gas-jet plasma was observed. Two stages of self-focusing of the laser pulse in the plasma were observed. Two groups of accelerated electrons were also observed associated with these stages of the channeling and is attributed to the betatron resonance acceleration mechanism. This is supported by 2D PIC simulations performed using code EPOCH and a detailed theoretical analysis which shows that present experimental conditions are more favorable for betatron resonance acceleration and generation of collimated, quasi-thermal/quasi-monoenergetic electron beams.
Inspired from the experimental information coming from LHC [2,3] and Babar [4] for radially higher excited charmed mesons, we predict the masses and decays of the n=2 S-wave and P- wave bottom mesons using the effective lagrangian approach. Using heavy quark effective theory approach, non-perturbative parameters (?, ?1 and ?2) are fitted using the available experimental and theoretical informations on charm masses. Using heavy quark symmetry and the values of these fitted parameters, the masses of radially excited even and odd parity bottom mesons with and without strangness are predicted. These predicted masses led in constraining the decay widths of these 12 states, and also shed light on the unknown values of the higher hadronic coupling constants eeg 2 SH and eeg 2 TH. Studying the properties like masses, decays of 2S and 2P states and some hadronic couplings would help forthcoming experiments to look into these states in future.
In the quest of understanding significant variations in the physical, chemical and electronic properties of the novel functional materials, low temperature Synchrotron X-ray Diffraction (LT-SXRD) measurements on CTO (a type-II) and CMTO (a type-I) multiferroics are presented. Magnetic phase diagram of CTO shows multiple magnetic transitions at zero fields, whereas, in CMTO, 20 K enhancement in the antiferromagnetic transition temperature is observed followed by near room temperature Griffiths phase. Rietveld analysis on LT-SXRD data of both the samples indicates important observations. For both CTO and CMTO, the magnetic anomalies are followed by structural anomalies, which is a clear signature of spin lattice coupling and the positive shift of spin lattice coupling from CTO to CMTO.
The importance of non-perturbative Quantum Chromodynamics [QCD] parameters is discussed in context to the predicting power for bottom meson masses and isospin splitting. In the framework of heavy quark effective theory, the work presented here focuses on the different allowed values of the two non perturbative QCD parameters used in heavy quark effective theory formula and using the best fitted parameter, masses of the excited bottom meson states in JP=(1/2)+ doublet in strange as well as non-strange sector are calculated here. The calculated masses are found to be matching well with experiments and other phenomenological models. The mass and hyperfine splitting has also been analyzed for both strange and non-strange heavy mesons with respect to spin and flavor symmetries.
The theory of heavy meson masses, in which the symmetries of heavy and light quarks are exploited, can be used to describe the low energy interaction among heavy mesons to a better extent. The spin-flavor symmetry leads to many interesting relations between the properties of hadrons containing a heavy quark. The most direct consequences concern the spectroscopy of such states. We use such symmetries to explore some of the states of B-meson and predictions are found to be in agreement with the experimental data.
The statistical model is implemented to find the magnetic moments of all octet baryons. The well-known sum rules like GMO and CG sum rules has been checked in order to check the consistency of our approach. The small discrepancy between the results suggests the importance of breaking in SU(3) symmetry.
The spin distributions, weak decay matrix elements for strange baryon octets with SU(3) breaking effects is studied. We systematically apply operator formalism along with statistical method to study JP= strange baryon octets for their low energy properties. Baryon is taken as an ensemble of quark-gluon Fock states in sea with three valence quarks to have spin-1/2, color-1 and flavor-8 quantum numbers. Detailed balance principle is applied to calculate the probabilities of each Fock states, with the inclusion of mass correction of strange quark in order to check the SU(3) breaking in weak decays constants and spin distributions. A dominant contribution from the vector sea is verified as compared to scalar and tensor sea, also the symmetry breaking correction leads to the deviations in the value of axial vector matrix elements ratio from experimental values by 17%. Present framework suggests a stronger base to choose statistical model with detailed balance principle to verify the experimental and theoretical values available and hence provide a deeper understanding to the strange baryon structure. Symmetry breaking effects lead to reduction in the values of axial matrix elements. Its contribution has a significant role in determining the validity of present approach.