arXiv subjects

A. Ali

Publications and source records attributed to A. Ali.

At least 37 records · Page 2Linked to original sources

arXiv2023

X-ray properties of high-redshift Radio Loud and Radio Quiet Quasars observed by Chandra

We performed a study of high redshift ($z>2$) quasars, looking for the main differences between Radio Loud Quasars (RLQ) and Radio Quiet Quasars (RQQ) in the X-ray band. Our sample of 472 RQQ and 81 RLQ was selected by cross-matching the SDSS DR7 quasars catalog with the Chandra Source Catalog. We computed the X-ray luminosity for the two samples and confirmed the X-ray luminosity excess of RLQ over RQQ. We fit the X-ray spectra assuming the absorbed power law model and obtained the photon index ($Γ$) values for all the sources in the sample. We excluded quasars with a low number of counts ($<10$) and large uncertainty on the best-fit photon index ($Γ_{err}>1$), and obtained the mean values of $Γ_{RLQ}=1.70 \hspace{0.5mm}_{-0.33}^{+0.36}$ and $Γ_{RQQ}=2.19 \hspace{0.5mm}_{-0.44}^{+0.46}$ for the RLQ and RQQ samples, respectively, showing that the RLQ have flatter (harder) X-ray spectra than RQQ. The Kuiper-two test confirms this result with the significant difference between the RLQ and RQQ photon index distributions ($D_{k}=0.37$ and P-value $= 10^{-6}$). We also evaluated the hardness ratio distributions and confirmed that the spectra of RLQ are flatter than the spectra of the RQQ. The RLQ's hard-to-soft ratio distribution is skewed towards the hard X-ray band, while the RQQ is towards the soft X-ray band. The hard-to-medium and medium-to-soft ratios show no difference.

astro-ph.HE↗

arXiv2022

Measurements of protons and charged pions emitted from $ν_μ$ charged-current interactions on iron at a mean neutrino energy of 1.49$\,$GeV using a nuclear emulsion detector

This study conducted an analysis of muons, protons, and charged pions emitted from $ν_μ$ charged-current interactions on iron using a nuclear emulsion detector. The emulsion detector with a 65$\,$kg iron target was exposed to a neutrino beam corresponding to 4.0$\times$10$^{19}$ protons on target with a mean neutrino energy of 1.49$\,$GeV. The measurements were performed at a momentum threshold of 200 (50)$\,$MeV/$c$ for protons (pions), which are the lowest momentum thresholds attempted up to now. The measured quantities are the multiplicities, emission angles, and momenta of the muons, protons, and charged pions. In addition to these inclusive measurements, exclusive measurements such as the muon-proton emission-angle correlations of specific channels and the opening angle between the protons of CC0$π$2$p$ events were performed. The data were compared to Monte Carlo (MC) predictions and some significant differences were observed. The results of the study demonstrate the capability of detailed measurements of neutrino-nucleus interactions using a nuclear emulsion detector to improve neutrino interaction models.

hep-ex↗

arXiv2022

Scintillator ageing of the T2K near detectors from 2010 to 2021

The T2K experiment widely uses plastic scintillator as a target for neutrino interactions and an active medium for the measurement of charged particles produced in neutrino interactions at its near detector complex. Over 10 years of operation the measured light yield recorded by the scintillator based subsystems has been observed to degrade by 0.9--2.2\% per year. Extrapolation of the degradation rate through to 2040 indicates the recorded light yield should remain above the lower threshold used by the current reconstruction algorithms for all subsystems. This will allow the near detectors to continue contributing to important physics measurements during the T2K-II and Hyper-Kamiokande eras. Additionally, work to disentangle the degradation of the plastic scintillator and wavelength shifting fibres shows that the reduction in light yield can be attributed to the ageing of the plastic scintillator.

physics.ins-det↗

arXiv2022

Interacting planetary nebulae III: Verification and galactic population based on the measurements of Gaia EDR3

The phenomenon of interaction between planetary nebulae (PNe) and the interstellar medium (ISM) is one of the significant issues in the field of astrophysics. The main objective of this paper is to verify the interaction process for objects that have been known as interacting PNe (IPNe) in the literature. This study is based on parallax and proper motion observations facilitated recently by the early third data release of the Gaia space mission. Based on the proper nebular central star (CS) motion towards the region of interaction between the PN and ISM, we were able to verify the interaction process for a group of 68 PNe and disprove the interaction process for a group of 33 PNe. The members of both groups were confirmed as genuine PN-ISM interacting objects in the literature. The members belonging to the 33 PNe group are false PN-ISM interacting objects that mimic the structure of IPNe. Moreover, we calculated the physical and kinematic properties of the verified group and analyzed their galactic population classification using reliable and precise measurements of the proper motion and parallax of the CS. We find that 41\% and 41\% of this group are associated with galactic thin and thick disks, respectively, while 18\% are members of thin or thick disks. The kinematical results show that the galactic thin-disk members have smaller vertical galactic heights, space velocities, and peculiar velocities than those belonging to the galactic thick disk.

astro-ph.SR↗

arXiv2022

A new statistical distance scale for planetary nebulae, based on Gaia EDR3

The present work aims to build a new statistical distance scale for planetary nebulae (PNe) based on a rigorous calibration sample. The distances of the calibration sample are derived from the trigonometric parallax method using the recent measurements of Gaia early third data release (Gaia EDR3). The new distance scale is created by applying the well-known linear relationship between the radio surface brightness temperature and the nebular radius. The calibration sample is made up of 96 PNe of accurately computed distances with uncertainties less than $20\%$. Earlier ground- and space-based trigonometric parallaxes of PNe display inconsistency with those of Gaia, particularly the HIPPARCOS results. In addition, these measurements have appreciably lower precision than that of Gaia. When compared to the trigonometric technique, the expansion and kinematic methods exhibited more consistency than the spectroscopic, extinction, gravity, and photo-ionization methods. Furthermore, contrary to earlier results in the literature, the extinction and gravity methods, on average, underestimate and slightly overestimate the PN distances. As a byproduct of extracting the Gaia parallaxes, we detect the radial velocity and variability for 14 and 3 PN central stars (CSs), respectively. To our knowledge, the variability of Hen 2-447 CS has been determined for the first time.

astro-ph.SR↗

arXiv2022

Superconducting properties of pseudobinary telluride Chevrel Phase Mo$_4$Re$_2$Te$_8$

Unconventional superconductivity in the Chevrel phase offers a wide structural aspect to understand the superconducting ground state. A detailed investigation on the superconducting properties of Re based pseudobinary telluride Chevrel phase Mo$_4$Re$_2$Te$_8$ is reported. It crystallizes in a trigonal structure with the space group $R\bar{3}H$ having superconducting transition temperature at $T_C$ = 3.26(3) K. Specific heat measurements suggests a fully gapped superconducting state; however, the proximity of upper critical field value from the Pauli limiting field can be attributed to unconventional nature.

cond-mat.supr-con↗

arXiv2022

Initial performance of the GlueX DIRC detector

The GlueX experiment at Jefferson Laboratory aims to perform quantitative tests of non-perturbative QCD by studying the spectrum of light-quark mesons and baryons. A Detector of Internally Reflected Cherenkov light (DIRC) was installed to enhance the particle identification (PID) capability of the GlueX experiment by providing clean $π$/K separation up to 3.7 GeV/$c$ momentum in the forward region ($θ<11^{\circ}$), which will allow the study of hybrid mesons decaying into kaon final states with significantly higher efficiency and purity. The new PID system is constructed with radiators from the decommissioned BaBar DIRC counter, combined with new compact photon cameras based on the SuperB FDIRC concept. The full system was successfully installed and commissioned with beam during 2019/2020. The initial PID performance of the system was evaluated and compared to one from Geant4 simulation.

physics.ins-det↗

arXiv2022

Electron angular correlation in neutrinoless double beta decay and new physics

The angular correlation of the electrons in the neutrinoless double beta decay ($0\nu2β$) is calculated taking into account the nucleon recoil, the $S$ and $P$-waves for the electrons and the electron mass using a general Lorentz invariant effective Lagrangian. We show that the angular coefficient is essentially independent of the nuclear matrix element models. We work out the angular coefficient in several scenarios for new physics, in particular, in the left-right symmetric models.

hep-ph↗

arXiv2022

Probing new physics in the Neutrinoless double beta decay using electron angular correlation

The angular correlation of the electrons emitted in the neutrinoless double beta decay ($0\nu2β$) is presented using a general Lorentz invariant effective Lagrangian for the leptonic and hadronic charged weak currents. We show that the coefficient $K$ in the angular correlation $dΓ/d\cos θ\propto (1-K\cos θ)$ is essentially independent of the nuclear matrix element models and present its numerical values for the five nuclei of interest ($^{76}{Ge}$, $^{82}{Se}$, $^{100}{Mo}$, $^{130}{Te}$, and $^{136}{Xe}$), assuming that the $0\nu2β$-decays in these nuclei are induced solely by a light Majorana neutrino, $ν_M$. This coefficient varies between $K=0.81$ (for the $^{76}{Ge}$ nucleus) and $K=0.88$ (for the $^{82}{Se}$ and $^{100}{Mo}$ nuclei), calculated taking into account the effects from the nucleon recoil, the $S$ and $P$-waves for the outgoing electrons and the electron mass. Deviation of $K$ from its values derived here would indicate the presence of New Physics (NP) in addition to a light Majorana neutrino, and we work out the angular coefficients in several $ν_M + {NP}$ scenarios for the $^{76}{Ge}$ nucleus. As an illustration of the correlations among the $0\nu2β$ observables (half-life $T_{1/2}$, the coefficient $K$, and the effective Majorana neutrino mass $|< m>|$) and the parameters of the underlying NP model, we analyze the left-right symmetric models, taking into account current phenomenological bounds on the right-handed $W_R$-boson mass and the left-right mixing parameter $ζ$.

hep-ph↗

arXiv2022

Search for photoproduction of axion-like particles at GlueX

We present a search for axion-like particles, $a$, produced in photon-proton collisions at a center-of-mass energy of approximately 4 GeV, focusing on the scenario where the $a$-gluon coupling is dominant. The search uses $a\toγγ$ and $a\toπ^+π^-π^0$ decays, and a data sample corresponding to an integrated luminosity of 168 pb$^{-1}$ collected with the GlueX detector. The search for $a\toγγ$ decays is performed in the mass range of $180 < m_a < 480$ MeV, while the search for $a\toπ^+π^-π^0$ decays explores the $600 < m_a < 720$ MeV region. No evidence for a signal is found, and 90% confidence-level exclusion limits are placed on the $a$-gluon coupling strength. These constraints are the most stringent to date over much of the mass ranges considered.

hep-ex↗

arXiv2022

Measurement of Spin Density Matrix Elements in $Λ(1520)$ Photoproduction at 8.2-8.8 GeV

We report on the measurement of spin density matrix elements of the $Λ(1520)$ in the photoproduction reaction $γp\rightarrow Λ(1520)K^+$, via its subsequent decay to $K^{-}p$. The measurement was performed as part of the GlueX experimental program in Hall D at Jefferson Lab using a linearly polarized photon beam with $E_γ=$ 8.2-8.8 GeV. These are the first such measurements in this photon energy range. Results are presented in bins of momentum transfer squared, $-(t-t_\text{0})$. We compare the results with a Reggeon exchange model and determine that natural exchange amplitudes are dominant in $Λ(1520)$ photoproduction.

nucl-ex↗

arXiv2021

Supernova Model Discrimination with Hyper-Kamiokande

Core-collapse supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants -- neutron stars and black holes -- are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of core-collapse supernovae is not yet well understood. Hyper-Kamiokande is a next-generation neutrino detector that will be able to observe the neutrino flux from the next galactic core-collapse supernova in unprecedented detail. We focus on the first 500 ms of the neutrino burst, corresponding to the accretion phase, and use a newly-developed, high-precision supernova event generator to simulate Hyper-Kamiokande's response to five different supernova models. We show that Hyper-Kamiokande will be able to distinguish between these models with high accuracy for a supernova at a distance of up to 100 kpc. Once the next galactic supernova happens, this ability will be a powerful tool for guiding simulations towards a precise reproduction of the explosion mechanism observed in nature.

astro-ph.IM↗

arXiv2021

First measurement using a nuclear emulsion detector of the $ν_μ$ charged-current cross section on iron around the 1$\,$GeV energy region

We have carried out $ν_μ$ charged-current interaction measurement on iron using an emulsion detector exposed to the T2K neutrino beam in the J-PARC neutrino facility. The data samples correspond to 4.0$\times$10$^{19}$ protons on target, and the neutrino mean energy is 1.49$\,$GeV. The emulsion detector is suitable for precision measurements of charged particles produced in neutrino-iron interactions with a low momentum threshold thanks to thin-layered structure and sub-$μ$m spatial resolution. The charged particles are successfully detected, and their multiplicities are measured using the emulsion detector. The cross section was measured to be $σ^{\mathrm{Fe}}_{\mathrm{CC}} = (1.28 \pm 0.11({\mathrm{stat.}})^{+0.12}_{-0.11}({\mathrm{syst.}})) \times 10^{-38} \, {\mathrm{cm}}^{2}/{\mathrm{nucleon}}$. The cross section in a limited kinematic phase space of induced muons, $θ_μ < 45^{\circ}$ and $p_μ > 400 \, {\rm MeV}/c$, on iron was $σ^{\mathrm{Fe}}_{\mathrm{CC \hspace{1mm} phase \hspace{0.5mm} space}} = (0.84 \pm 0.07({\mathrm{stat.}})^{+0.07}_{-0.06}({\mathrm{syst.}})) \times 10^{-38} \, {\mathrm{cm}}^{2}/{\mathrm{nucleon}}$. The cross-section results are consistent with previous values obtained via different techniques using the same beamline, and they are well reproduced by current neutrino interaction models. These results demonstrate the capability of the detector towards the detailed measurements of the neutrino-nucleus interactions around the 1$\,$GeV energy region.

hep-ex↗

arXiv2021

Improved constraints on neutrino mixing from the T2K experiment with $\mathbf{3.13\times10^{21}}$ protons on target

The T2K experiment reports updated measurements of neutrino and antineutrino oscillations using both appearance and disappearance channels. This result comes from an exposure of $14.9~(16.4) \times 10^{20}$ protons on target in neutrino (antineutrino) mode. Significant improvements have been made to the neutrino interaction model and far detector reconstruction. An extensive set of simulated data studies have also been performed to quantify the effect interaction model uncertainties have on the T2K oscillation parameter sensitivity. T2K performs multiple oscillation analyses that present both frequentist and Bayesian intervals for the PMNS parameters. For fits including a constraint on \ssqthonethree from reactor data and assuming normal mass ordering T2K measures $\sin^2θ_{23} = 0.53^{+0.03}_{-0.04}$ and $Δm^2_{32} = (2.45 \pm 0.07) \times 10^{-3}$ eV$^{2}$c$^{-4}$. The Bayesian analyses show a weak preference for normal mass ordering (89% posterior probability) and the upper $\sin^2θ_{23}$ octant (80% posterior probability), with a uniform prior probability assumed in both cases. The T2K data exclude CP conservation in neutrino oscillations at the $2σ$ level.

hep-ex↗

arXiv2021

First T2K measurement of transverse kinematic imbalance in the muon-neutrino charged-current single-$π^+$ production channel containing at least one proton

This paper reports the first T2K measurement of the transverse kinematic imbalance in the single-$π^+$ production channel of neutrino interactions. We measure the differential cross sections in the muon-neutrino charged-current interaction on hydrocarbon with a single $π^+$ and at least one proton in the final state, at the ND280 off-axis near detector of the T2K experiment. The extracted cross sections are compared to the predictions from different neutrino-nucleus interaction event generators. Overall, the results show a preference for models which have a more realistic treatment of nuclear medium effects including the initial nuclear state and final-state interactions.

hep-ex↗

arXiv2021

An investigation of planetary nebulae accompanying PG1159 central stars, based on Gaia DR2 measurements

This article discusses the physical and kinematical characteristics of planetary nebulae accompanying PG1159 central stars. The study is based on the parallax and proper motion measurements recently offered by Gaia space mission. Two approaches were used to investigate the kinematical properties of the sample. The results revealed that most of the studied nebulae arise from progenitor stars of mass range; $0.9-1.75$\,M$_{\odot}$. Furthermore, they tend to live within the Galactic thick-disk and moving with an average peculiar velocity of $61.7\pm19.2$\,km\,s$^{-1}$ at a mean vertical height of $469\pm79$ pc. The locations of the PG1159 stars on the H-R diagram indicate that they have an average final stellar mass and evolutionary age of $0.58\pm0.08$\,M$_{\odot}$ and $25.5\pm5.3 \rm{x}10^3$ yr, respectively. We found a good agreement between the mean evolutionary age of the PG1159 stars and the mean dynamical age of their companion planetary nebulae ($28.0\pm6.4 \rm{x}10^3$ yr).

astro-ph.SR↗

arXiv2021

The PANDA DIRCs

The PANDA experiment at the FAIR facility adresses open questions in hadron physics with antiproton beams in the momentum range of 1.5-15 GeV/c. The antiprotons are stored and cooled in a High Energy Storage RING (HESR) with a momentum spread down to Dp/p = 4*10^-5. A high luminosity of up to 2*10^32 cm-2 s-1 can be achieved. An excellent hadronic particle identification (PID) will be provided by two Cherenkov detectors using the priciple of Detection of Internally Reflected Cherenkov light (DIRC). In the forward direction from polar angles of 5 degree to 22 degree, the Endcap Disc DIRC (EDD) separates pions from kaons up to momenta of 4 GeV/c. Between 22 degree and 140 degree the Barrel DIRC cleanly separates pions from kaons for momenta up to 3.5 GeV/c. This article describes the design of the Barrel DIRC and of the Endcap Disc DIRC and the validation of their designs in particle beams at the CERN PS.

physics.ins-det↗

arXiv2021

Constraint on the Matter-Antimatter Symmetry-Violating Phase in Neutrino Oscillations

The current laws of physics do not explain the observed imbalance of matter and antimatter in the universe. Sakharov proposed that an explanation would require the violation of CP symmetry between matter and antimatter. The only CP violation observed so far is in the weak interactions of quarks, and it is too small to explain the matter-antimatter imbalance of the universe. It has been shown that CP violation in the lepton sector could generate the matter-antimatter disparity through the process called leptogenesis. The quantum mixing of neutrinos, the neutral leptons in the Standard Model, provides a potential source of CP violation through a complex phase dCP, which may have consequences for theoretical models of leptogenesis. This CP violation can be measured in muon neutrino to electron neutrino oscillations and the corresponding antineutrino oscillations, which are experimentally accessible with accelerator-produced beams as established by the T2K experiment. Until now, the value of dCP has not been significantly constrained by neutrino oscillation experiments. Here the T2K collaboration reports a measurement that favors large enhancement of the neutrino oscillation probability, excluding values of dCP which result in a large enhancement of the observed anti-neutrino oscillation probability at three standard deviations (3 sigma). The 3 sigma confidence level interval for dCP, which is cyclic and repeats every 2pi, is [-3.41,-0.03] for the so-called normal mass ordering, and [-2.54,-0.32] for the inverted mass ordering. Our results show an indication of CP violation in the lepton sector. Herein we establish methods for sensitive searches for matter-antimatter asymmetry in neutrino oscillations using accelerator-produced neutrino beams. Future measurements with larger data samples will determine whether the leptonic CP violation is larger than the quark sector CP violation.

hep-ex↗