arXiv subjects
Publications and source records attributed to S. Bhattacharya.
This paper summarizes the relevant theoretical developments, outlines some ideas to improve experimental searches for free neutron-antineutron oscillations, and suggests avenues for future improvement in the experimental sensitivity.
The even-even nucleus $^{26}$Mg has been studied through the reaction $^{27}$Al(d,$^{3}$He) at 25 MeV beam energy. The spectroscopic factors have been extracted upto 7.50 MeV excitation energy using local, zero range distorted wave Born approximation. The comparison of the spectroscopic factors have been done with previously reported values using the same reaction probe. The extracted spectroscopic factors for different excited states were found to be in good agreement with the previously reported values for the same. The present results were also compared with the predictions from shell model as well as rotational model. The analog states of $^{26}$Al and $^{26}$Mg were found to be in good agreement.
Mass distributions of the fragments in the fission of $^{206}$Po and the N=126 neutron shell closed nucleus $^{210}$Po have been measured. No significant deviation of mass distributions has been found between $^{206}$Po and $^{210}$Po, indicating the absence of shell correction at the saddle point in both the nuclei, contrary to the reported angular anisotropy and pre-scission neutron multiplicity results. This new result provides benchmark data to test the new fission dynamical models to study the effect of shell correction on the potential energy surface at saddle point.
Constraining excitation energy at which nuclear shell effect washes out has important implications on the production of super heavy elements and many other fields of nuclear physics research. We report the fission fragment mass distribution in alpha induced reaction on an actinide target for wide excitation range in close energy interval and show direct evidence that nuclear shell effect washes out at excitation energy ~40 MeV. Calculation shows that second peak of the fission barrier also vanishes around similar excitation energy.
High-spin states in the doubly-odd $^{198}$Bi nucleus have been studied by using the $^{185,187}$Re($^{16}$O, xn) reactions at the beam energy of 112.5 MeV. $γ-γ$ coincidence were measured by using the INGA array with 15 Compton suppressed clover HPGe detectors. The observed levels have been assigned definite spin-parity. The high spin structure is grouped into three bands (B1, B2 and B3), of which two (B1 and B2) exhibit the properties of magnetic rotation (MR). Tilted axis cranking calculations were carried out to explain the MR bands having large multi-quasiparticle configurations. The calculated results explain the bands B1 and B2 very nicely, confirming the shears mechanism and suggest a crossing of two MR bands in both the cases. The crossing is from 6-qp to 8-qp in band B1 and from 4-qp to 6-qp in band B2, a very rare finding. A semiclassical model has also been used to obtain the particle-hole interaction strengths for the bands B1 and B2, below the band crossing.
We observe electro-hydrodynamically driven turbulent flows at low Reynolds numbers in a two-fluid emulsion consisting of micron-scale droplets. In the presence of electric fields, the droplets produce interacting hydrodynamic flows which result in a dynamical organization at a spatial scale much larger than the size of the individual droplets. We characterize the dynamics associated with these structures by both video imaging and a simultaneous, in situ, measurement of the time variation of the bulk Reynolds stress with a rheometer. The results display scale invariance in the energy spectra in both space and time.
We report on the spreading of triboelectrically charged glass particles on an oppositely charged surface of a plastic cylindrical container in the presence of a constant mechanical agitation. The particles spread via sticking, as a monolayer on the cylinder's surface. Continued agitation initiates a sequence of instabilities of this monolayer, which first forms periodic wavy-stripe-shaped transverse density modulation in the monolayer and then ejects narrow and long particle-jets from the tips of these stripes. These jets finally coalesce laterally to form a homogeneous spreading front that is layered along the spreading direction. These remarkable growth patterns are related to a time evolving frictional drag between the moving charged glass particles and the countercharges on the plastic container. The results provide insight into the multiscale time-dependent tribolelectric processes and motivates further investigation into the microscopic causes of these macroscopic dynamical instabilities and spatial structures.
We present a measurement of the angular bispectrum of the millimeter-wave sky in observing bands centered at roughly 95, 150, and 220 GHz, on angular scales of $1^\prime \lesssim θ\lesssim 10^\prime$ (multipole number $1000 \lesssim l \lesssim 10000$). At these frequencies and angular scales, the main contributions to the bispectrum are expected to be the thermal Sunyaev-Zel'dovich (tSZ) effect and emission from extragalactic sources, predominantly dusty, star-forming galaxies (DSFGs) and active galactic nuclei. We measure the bispectrum in 800 $\mathrm{deg}^2$ of three-band South Pole Telescope data, and we use a multi-frequency fitting procedure to separate the bispectrum of the tSZ effect from the extragalactic source contribution. We simultaneously detect the bispectrum of the tSZ effect at $>$10$σ$, the unclustered component of the extragalactic source bispectrum at $>$5$σ$ in each frequency band, and the bispectrum due to the clustering of DSFGs---i.e., the clustered cosmic infrared background (CIB) bispectrum---at $>$5$σ$. This is the first reported detection of the clustered CIB bispectrum. We use the measured tSZ bispectrum amplitude, compared to model predictions, to constrain the normalization of the matter power spectrum to be $σ_8 = 0.787 \pm 0.031$ and to predict the amplitude of the tSZ power spectrum at $l = 3000$. This prediction improves our ability to separate the thermal and kinematic contributions to the total SZ power spectrum. The addition of bispectrum data improves our constraint on the tSZ power spectrum amplitude by a factor of two compared to power spectrum measurements alone and demonstrates a preference for a nonzero kinematic SZ (kSZ) power spectrum, with a derived constraint on the kSZ amplitude at $l=3000$ of A_kSZ $ = 2.9 \pm 1.6 \ μ$K$^2$, or A_kSZ $ = 2.6 \pm 1.8 \ μ$K$^2$ if the default A_kSZ > 0 prior is removed.
This report, prepared for the Community Planning Study - Snowmass 2013 - summarizes the theoretical motivations and the experimental efforts to search for baryon number violation, focussing on nucleon decay and neutron-antineutron oscillations. Present and future nucleon decay search experiments using large underground detectors, as well as planned neutron-antineutron oscillation search experiments with free neutron beams are highlighted.
This report summarizes the work of the Energy Frontier Top Quark working group of the 2013 Community Summer Study (Snowmass).
The excited states in the odd-$A$ $^{197}$Tl nucleus have been studied by populating them using the $^{197}$Au($α$, 4$n$)$^{197}$Tl reaction at the beam energy of 48 MeV. The $γ-γ$ coincidence data were taken using a combination of clover, LEPS and single crystal HPGe detectors. Precise spin and parity assignments of the excited states have been done through the polarization and the DCO measurements. A new band structure has been identified and the evidence for a possible intruder $πi_{13/2}$ state has been found for the first time. Possible configurations of the observed bands have been discussed. The total Routhian surface calculations have been performed to study the shape of $^{197}$Tl for different configurations.
This report summarizes the work of the Energy Frontier New Physics working group of the 2013 Community Summer Study (Snowmass).
This paper summarizes discussions of the theoretical developments and the studies performed by the NNbarX collaboration for the 2013 Snowmass Community Summer Study.
The lensing power spectrum from cosmic microwave background (CMB) temperature maps will be measured with unprecedented precision with upcoming experiments, including upgrades to ACT and SPT. Achieving significant improvements in cosmological parameter constraints, such as percent level errors on sigma_8 and an uncertainty on the total neutrino mass of approximately 50 meV, requires percent level measurements of the CMB lensing power. This necessitates tight control of systematic biases. We study several types of biases to the temperature-based lensing reconstruction signal from foreground sources such as radio and infrared galaxies and the thermal Sunyaev-Zel'dovich effect from galaxy clusters. These foregrounds bias the CMB lensing signal due to their non-Gaussian nature. Using simulations as well as some analytical models we find that these sources can substantially impact the measured signal if left untreated. However, these biases can be brought to the percent level if one masks galaxies with fluxes at 150 GHz above 1 mJy and galaxy clusters with masses above M_vir = 10^14 M_sun. To achieve such percent level bias, we find that only modes up to a maximum multipole of l_max ~ 2500 should be included in the lensing reconstruction. We also discuss ways to minimize additional bias induced by such aggressive foreground masking by, for example, exploring a two-step masking and in-painting algorithm.
We measure the cross-power spectrum of the projected mass density as traced by the convergence of the cosmic microwave background lensing field from the South Pole Telescope (SPT) and a sample of Type 1 and 2 (unobscured and obscured) quasars at z~1 selected with the Wide-field Infrared Survey Explorer, over 2500 deg^2. The cross-power spectrum is detected at ~7-sigma, and we measure a linear bias b=1.67+/-0.24, consistent with clustering analyses. Using an independent lensing map, derived from Planck observations, to measure the cross-spectrum, we find excellent agreement with the SPT analysis. The bias of the combined sample of Type 1 and 2 quasars determined in this work is similar to that previously determined for Type 1 quasars alone; we conclude that that obscured and unobscured quasars must trace the matter field in a similar way. This result has implications for our understanding of quasar unification and evolution schemes.
Snowmass is a US long-term planning study for the high-energy community by the American Physical Society's Division of Particles and Fields. For its simulation studies, opportunistic resources are harnessed using the Open Science Grid infrastructure. Late binding grid technology, GlideinWMS, was used for distributed scheduling of the simulation jobs across many sites mainly in the US. The pilot infrastructure also uses the Parrot mechanism to dynamically access CvmFS in order to ascertain a homogeneous environment across the nodes. This report presents the resource usage and the storage model used for simulating large statistics Standard Model backgrounds needed for Snowmass Energy Frontier studies.
If the only contribution to neutrinoless double beta decay (NLDBD) are neutrino masses its discovery may be very difficult, especially if neutrinos present a normal hierarchy spectrum. However, this is not the only possibility; NLDBD can in general produce electrons of either chirality, in contrast with the neutrino induced NLDBD which predicts two left-handed electrons. Using an effective Lagrangian approach we classify the lepton number violating (LNV) effective operators with two leptons of either chirality but no quarks, ordered according to the magnitude of their contribution to NLDBD. We point out that, for each of the three chirality assignments, $e_{L}e_{L},e_{L}e_{R}$ and $e_{R}e_{R}$, there is only one LNV operator of the corresponding type to lowest order, and these have dimensions 5, 7 and 9, respectively. Neutrino masses are always induced by these extra operators but can be delayed to one (dimension 7) or two loops (dimension 9). Under the assumption that NLDBD is dominated by the operators of dimension 7 or 9 we find that the scale of new physics should be relatively low ($\lesssim 30$ TeV). We also list the SM additions generating these operators upon integration of the heavy modes, and discuss simple realistic examples of renormalizable theories for each case. The phenomenology of a model giving rise to the dimension 9 operator has been analyzed with some detail: if NLDBD is going to be seen in the next round of experiments, the doubly charged scalars of the model could be seen at the LHC and lepton flavour violating (LFV) rates could be at the reach of foreseen experiments. Moreover neutrino masses, which arise at two loops, display a very particular structure and are strongly constrained, in fact, $\sin^{2}θ_{13}\gtrsim0.008$, when $μ\rightarrow eee$ is required to lie below its present experimental limit.
We use a temperature map of the cosmic microwave background (CMB) obtained using the South Pole Telescope at 150 GHz to construct a map of the gravitational convergence to z ~ 1100, revealing the fluctuations in the projected mass density. This map shows individual features that are significant at the ~ 4 sigma level, providing the first image of CMB lensing convergence. We cross-correlate this map with Herschel/SPIRE maps covering 90 square degrees at wavelengths of 500, 350, and 250 microns. We show that these submillimeter-wavelength (submm) maps are strongly correlated with the lensing convergence map, with detection significances in each of the three submm bands ranging from 6.7 to 8.8 sigma. We fit the measurement of the cross power spectrum assuming a simple constant bias model and infer bias factors of b=1.3-1.8, with a statistical uncertainty of 15%, depending on the assumed model for the redshift distribution of the dusty galaxies that are contributing to the Herschel/SPIRE maps.