arXiv subjects

S. S. Alam

Publications and source records attributed to S. S. Alam.

9 recordsLinked to original sources

arXiv2026

Evidence of the Excited X(5)-like Critical-Point Symmetry Structures in 152Sm

The positive-parity structure of 152Sm has been investigated through high-statistics γ-ray spectroscopy following the (150Nd(α,2n)152Sm reaction at Elab = 26 MeV. Several collective structures built on excited 0+ states have been extended through the observation of new levels and γ-ray transitions, and spin-parity assignments have been established using directional-correlation and linear-polarization measurements. Electromagnetic transition strengths (B(E2)), deduced from measured branching ratios and known level lifetimes, reveal pronounced collectivity among the excited configurations. The resulting level scheme provides evidence for a sequence of excited collective bands extending beyond the well-known ground-state and first excited 0+ structures. The excitation energies and transition strengths are examined within the framework of the X(5) critical-point description of the first-order U(5)-SU(3) shape-phase transition. In addition to the established X(5)-like features of the low-lying spectrum, the observed systematics of the higher-lying bands are found to be consistent with excited collective structures exhibiting X(5)-like characteristics. The results provide new constraints on the realization of critical-point behavior in finite nuclei and on the evolution of collectivity in the N=90 region.

nucl-ex↗

arXiv2026

Low lying excitations in $^{150}$Pm

The low lying excitations in odd-odd $^{150}$Pm have been studied through proton induced reaction with an array of five Compton suppressed Clover HPGe and one segmented planar Ge detectors. The relative excitation functions for the observed $γ$ rays have been studied using singles data at two beam energies of 8~MeV and 9~MeV. 16 new $γ$ rays and 15 new levels have been placed in the level scheme of $^{150}$Pm based on $γ-γ$ coincidence data. The relative intensities for the observed $γ$ rays have been determined using total and gated projections. Tentative spin-parity assignments were made to few low lying excitations of $^{150}$Pm, using limited angular distribution data and other information. Lifetimes were estimated for two excited levels in this nucleus using using generalized centroid difference analysis, applied in the nanosecond range, with Ge detectors. Large basis shell model and projected shell model calculation were performed to interpret the experimentally observed levels. The present work indicates 1$^-$ ground state, a 2$^-$ state close to the ground state ($\sim$50~keV) and a low lying 6$^-$ isomeric state in this odd-odd nucleus along with emerging band structures developed with two quasiparticle configurations.

nucl-ex↗

arXiv2026

Hindered $ΔK=1$ Dipole Strength in octupole bands in $N=90$ $^{154}$Gd from Lifetime Measurements with $γ-γ$ fast timing technique

The lifetimes of the low-lying negative-parity $1^-$ state at 1414~keV and $2^-$ state at 1398~keV in $^{154}$Gd have been measured using the $γ$--$γ$ fast-timing technique with the VENTURE array at VECC, Kolkata. The states were populated through the $β$ decay of $^{154}$Tb, produced in proton-induced reactions at the K130 cyclotron. From the measured lifetimes, absolute $B(E1)$ transition strengths were deduced. The extracted $B(E1)$ values are compared with those of neighboring Gd isotopes and with Gogny-HFB-based $sdf$-IBM calculations. The results show that the measured $E1$ strengths from these states are strongly hindered compared with the corresponding $ΔK=0$ transitions, providing evidence for weak $ΔK=1$ dipole strength in $^{154}$Gd.

nucl-ex↗

arXiv2026

Lifetimes and Transition Probabilities in $N = 76 ^{130}Xe$

Lifetimes for the ${4}_1^+$ and ${6}_1^+$ states have been directly measured using $γ-γ$ fast timing technique for low lying states of $^{130}Xe$, populated from $β^-$ decay of the parent $^{130}I$ produced through $^{nat}U(α,f)$ reaction at $E_α~=~40~MeV$. VENTURE array comprising of eight fast CeBr$_3$ detectors is used for lifetime measurement. The reduced transition probabilities deduced from the measured lifetimes have been compared with theoretical values obtained from the large basis shell model calculation and the interacting boson approximation (IBM) calculation.

nucl-ex↗

arXiv2025

A New Evidence of Interplay Between Tetrahedral and Octahedral Symmetries and Symmetry Breaking: Exotic Rotational Bands in $^{152}$Sm

We report on an experimental evidence for a new, second tetrahedral band in $^{152}_{\;\;62}$Sm$^{}_{90}$. It was populated via fusion evaporation reaction, $^{150}{\rm Nd}(α, 2n)^{152}$Sm, employing 26 MeV beam of $α$ particles from K-130 cyclotron at Variable Energy Cyclotron Centre, Kolkata, India. The newly observed possible mixed parity sequence with absence of E2 and strong indication of E3 transitions is consistent with the spectroscopic criteria for a tetrahedral-symmetry rotational band that could be constructed from the allowed spin-parity assignments. This structure differs from the structure of the band previously found in the same nucleus, the new one manifesting tetrahedral symmetry not accompanied by the octahedral one. Our new experimental results are interpreted in terms of group representation theory and collective nuclear-motion theory of Bohr. We propose to generalize the notion of the tetrahedral vibrational bands and believe that our new experimental results support a number of theory predictions related to nuclear tetrahedral symmetry published earlier and bring a new light into the issue of spontaneous symmetry breaking in heavy nuclei.

nucl-ex↗

arXiv2019

Study of radioactivity built-up and decay with singles time-stamped data

Time-stamped data have been used to estimate the decay half-lives of radioactive 118mSb and 64,66,68Ga nuclei. These nuclei are populated through the reaction 4He (Elab = 32 MeV) + nat In and p (Elab = 10 MeV) + natZn, respectively. The g -rays emitted by the excited daughter nuclei are detected by a single high purity germanium (HPGe) detector and the data are acquired using a CAEN 5780M desktop digitizer. Half-lives of different orders of magnitudes for the above mentioned nuclei are obtained from both the decay of parent and the growth of daughter nuclei. It is observed that the half-lives obtained from both these techniques match fairly well and also are consistent with the reported values. It is demonstrated that the time-stamped data can be useful while studying certain half-lives which are too long for measurement using in-beam electronic technique and too short for decay studies in off-beam methods. The data also have a special relevance for constant monitoring of beam current and beam-tuning.

physics.ins-det↗

arXiv2017

Identification of a long lived $β$ decaying isomer in $^{150}$Pm

The decay of odd-odd $^{150}$Pm has been studied by populating the nucleus with the $^{150}$Nd(p,n)$^{150}$Pm reaction at E$_{beam}$ = 8.0 MeV using 97$\%$ enriched $^{150}$Nd target. The presence of an isomeric state with $β$ decay half life of 2.2(1) h could be identified in $^{150}$Pm by following the half lives of the observed $γ$ transitions. The decay of the isomer to the excited levels of $^{150}$Sm has been confirmed by observing the $γ- γ$ coincidence with the VENUS array of six Compton suppressed Clover HPGe detectors. The $β$ decay end-point energies corresponding to the decay from the $^{150g}$Pm and $^{150m}$Pm have been measured using a $β-γ$ coincidence setup of two thin window Planar HPGe detectors and four Clover HPGe detectors of the VENUS array. The systematics of the similar isomeric states in neighboring nuclei has been studied to understand the underlying structure of these states. Shell model calculation has been performed by using OXBASH code which indicates the presence of a 5$^-$ isomeric state at very low excitation in the nucleus. The calculation also suggests hindered electromagnetic decay of this isomer and supports the possibility of its $β$ decay to the excited levels of $^{150}$Sm.

nucl-ex↗

arXiv2012

The Blanco Cosmology Survey: Data Acquisition, Processing, Calibration, Quality Diagnostics and Data Release

The Blanco Cosmology Survey (BCS) is a 60 night imaging survey of $\sim$80 deg$^2$ of the southern sky located in two fields: ($α$,$δ$)= (5 hr, $-55^{\circ}$) and (23 hr, $-55^{\circ}$). The survey was carried out between 2005 and 2008 in $griz$ bands with the Mosaic2 imager on the Blanco 4m telescope. The primary aim of the BCS survey is to provide the data required to optically confirm and measure photometric redshifts for Sunyaev-Zel'dovich effect selected galaxy clusters from the South Pole Telescope and the Atacama Cosmology Telescope. We process and calibrate the BCS data, carrying out PSF corrected model fitting photometry for all detected objects. The median 10$σ$ galaxy (point source) depths over the survey in $griz$ are approximately 23.3 (23.9), 23.4 (24.0), 23.0 (23.6) and 21.3 (22.1), respectively. The astrometric accuracy relative to the USNO-B survey is $\sim45$ milli-arcsec. We calibrate our absolute photometry using the stellar locus in $grizJ$ bands, and thus our absolute photometric scale derives from 2MASS which has $\sim2$% accuracy. The scatter of stars about the stellar locus indicates a systematics floor in the relative stellar photometric scatter in $griz$ that is $\sim$1.9%, $\sim$2.2%, $\sim$2.7% and$\sim$2.7%, respectively. A simple cut in the AstrOmatic star-galaxy classifier {\tt spread\_model} produces a star sample with good spatial uniformity. We use the resulting photometric catalogs to calibrate photometric redshifts for the survey and demonstrate scatter $δz/(1+z)=0.054$ with an outlier fraction $η<5$% to $z\sim1$. We highlight some selected science results to date and provide a full description of the released data products.

astro-ph.CO↗

arXiv2006

Border Collision Bifurcations in n-Dimensional Piecewise Linear Discontinuous Maps

In this paper we report some important results that help in analizing the border collision bifurcations that occur in n-dimensional discontinuous maps. For this purpose, we use the piecewise linear approximation in the neighborhood of the plane of discontinuity. Earlier, Feigin had made a similar analysis for general n-dimensional piecewise smooth continuous maps. Proceeding along similar lines, we obtain the general conditions of existence of period-1 and period-2 fixed points before and after a border collision bifurcation. The application of the method is then illustrated using a specific example of a two-dimensional discontinuous map.

nlin.CD↗