Thermionic electron beam is a fundamental part of all types of linear accelerators around the world in the field of Experimental High Energy Physics. Thermionic beam is very inexpensive and simple to produce. In this ...Thermionic electron beam is a fundamental part of all types of linear accelerators around the world in the field of Experimental High Energy Physics. Thermionic beam is very inexpensive and simple to produce. In this work, we give an overview of generation, design and applications of the electron beam with particular reference to e-beam generation at high energy linear accelerators. Experimental data are presented in tabular form for ready reference. We also make an evaluation of these high energy sources with our in-house designed e-beam gun. Finally, a comparison has been presented in terms of characteristic parameters of all these high performance sources.展开更多
This study aims to discuss anisotropic solutions that are spherically symmetric in the quintessence field,which describe compact stellar objects in the modified Rastall teleparallel theory of gravity.To achieve this g...This study aims to discuss anisotropic solutions that are spherically symmetric in the quintessence field,which describe compact stellar objects in the modified Rastall teleparallel theory of gravity.To achieve this goal,the Krori and Barua arrangement for spherically symmetric components of the line element is incorporated.We explore the field equations by selecting appropriate off-diagonal tetrad fields.Born-Infeld function of torsion f(T)=β√λT+1-1 and power law form h(T)=δTn are used.The Born-Infeld gravity was the first modified teleparallel gravity to discuss inflation.We use the linear equation of state pr=ξρto separate the quintessence density.After obtaining the field equations,we investigate different physical parameters that demonstrate the stability and physical acceptability of the stellar models.We use observational data,such as the mass and radius of the compact star candidates PSRJ 1416-2230,Cen X-3,&4U 1820-30,to ensure the physical plausibility of our findings.展开更多
The mechanical, electronic and magnetic properties of non-magnetic MgTe and ferro-magnetic (FM) Mgo.75 TM025 Te (TM = Fe, Co, Ni) in the zinc-blende phase are studied by ab-initio calculations for the first time. ...The mechanical, electronic and magnetic properties of non-magnetic MgTe and ferro-magnetic (FM) Mgo.75 TM025 Te (TM = Fe, Co, Ni) in the zinc-blende phase are studied by ab-initio calculations for the first time. We use the generalized gradient approximation functional for computing the structural stability, and mechanical properties, while the modified Becke and Johnson local (spin) density approximation (mBJLDA) is utilized for determining the electronic and magnetic properties. By comparing the energies of non-magnetic and FM calculations, we find that the compounds are stable in the FM phase, which is confirmed by their structural stabilities in terms of enthalpy of formation. Detailed descriptions of elastic properties of Mgo.75TMo.25Te alloys in the FM phase are also presented. For electronic properties, the spin- polarized electronic band structures and density of states are computed, showing that these compounds are direct bandgap materials with strong hybridizations of TM 3d states and Te p states. Further, the ferromagnetism is discussed in terms of the Zener free electron model, RKKY model and double exchange model. The charge density contours in the (110) plane are calculated to study bonding properties. The spin exchange splitting and crystal field splitting energies are also calculated. The distribution of electron spin density is employed in computing the magnetic moments appearing at the magnetic sites (Fe, Co, Ni), as well as at the non-magnetic sites (Mg, Te). It is found that the p-d hybridization causes not only magnetic moments on the magnetic sites but also induces negligibly small magnetic moments at the non-magnetic sites.展开更多
Free falling hypersurfaces in the Schwarzschild geometry have been studied to provide a complete foliation of spacetime. The hypersurfaces do not cross into the maximally extended spacetime and are well behaved everyw...Free falling hypersurfaces in the Schwarzschild geometry have been studied to provide a complete foliation of spacetime. The hypersurfaces do not cross into the maximally extended spacetime and are well behaved everywhere except at the singularity r =0 the mean extrinsic curvature becomes infinity.展开更多
Ultra-light axions(ULAs)with mass less than 10-20 eV have interesting behaviors that may contribute to either dark energy or dark matter at different epochs of the Universe.Their properties can be explored by cosmolog...Ultra-light axions(ULAs)with mass less than 10-20 eV have interesting behaviors that may contribute to either dark energy or dark matter at different epochs of the Universe.Their properties can be explored by cosmological observations,such as expansion history of the Universe,cosmic large-scale structure,cosmic microwave background,etc.In this work,we study the ULAs with mass around 10-33 eV,which means that the ULA field still rolls slowly at present with the equation of state w=-1 as dark energy.To investigate the mass and other properties of this kind of ULA field,we adopt the measurements of Type Ia supernova(SN Ia),baryon acoustic oscillation(BAO),and Hubble parameter H(z).The Markov Chain Monte Carlo(MCMC)technique is employed to perform the constraints on the parameters.Finally,by exploring four cases of the model,we find that the mass of this ULA field is about 3×10-33 eV if assuming the initial axion fieldφi=Mpl.We also investigate a general case by assumingφi≤Mpl,and find that the fitting results ofφi/Mpl are consistent with or close to 1 for the datasets that we use.展开更多
Using theΣ-form factor it is shown that the Donnachie-Landshoff pomeron gives a good description of the high energy total and elastic differential cross-section data forΣ-p scattering.
Most recent data for the differential cross section and polarisation for the hypercharge exchange reaction π+p → K+Σ+ and its line-reversed partners is explained by using the simple Regge pole model with phenomenol...Most recent data for the differential cross section and polarisation for the hypercharge exchange reaction π+p → K+Σ+ and its line-reversed partners is explained by using the simple Regge pole model with phenomenological residue functions.展开更多
The differential cross section data for high energy K-p elastic scattering showing a break near-t=4(Gev/c)^(2) have been fitted for pL=20,100 and 200GeV/c with-t extended up to 14(Gev/c)^(2) by using a dipole pomeron ...The differential cross section data for high energy K-p elastic scattering showing a break near-t=4(Gev/c)^(2) have been fitted for pL=20,100 and 200GeV/c with-t extended up to 14(Gev/c)^(2) by using a dipole pomeron mode.展开更多
Beginning with precise data on the ratio of structure functions in deep inelastic scattering(DIS)from ^3He and ^3H,collected on the domain 0.19≤xB≤0.83,where xBis the Bjorken scaling variable,we employ a robust meth...Beginning with precise data on the ratio of structure functions in deep inelastic scattering(DIS)from ^3He and ^3H,collected on the domain 0.19≤xB≤0.83,where xBis the Bjorken scaling variable,we employ a robust method for extrapolating such data to arrive at a model-independent result for the xB=1 value of the ratio of neutron and proton structure functions.Combining this with information obtained in analyses of DIS from nuclei,corrected for target-structure dependence,we arrive at a prediction for the proton valence-quark ratio:d_(v)/u_(v)|_(xB→1)=0.230(57).Requiring consistency with this result presents a challenge to many descriptions of proton structure.展开更多
The mass concentrations of eighteen airborne samples collected from Lahore (Pakistan) are found in the range from 595 to 3027μg/m3with average value of 1130 μg/m3. Most of these values are normal and as reported in ...The mass concentrations of eighteen airborne samples collected from Lahore (Pakistan) are found in the range from 595 to 3027μg/m3with average value of 1130 μg/m3. Most of these values are normal and as reported in the literature for other parts of the world. The major phases identified in the samples by the X-ray powder diffraction technique are Albite (Anorthite), Calcite, Clinochlore (Chlorite), Gypsum, Illite, Quartz and Talc which have also been reported by other researchers to be present in the airborne particulates of other world locations. The average weight percentages of the phases (minerals) in the samples are respectively 15.5, 10.6, 23.7, 2.4, 19.1, 20.2, and 8.5. Some of the elements (e.g., boron, cadmium, lithium, manganese, titanium, and zinc) quantified in two samples determined using a spark-source mass spectrometer appear also to derive their origin from man-made activities. However no compound synthesized in the atmosphere is detected by the X-ray diffraction method.展开更多
We present structural,magnetic and optical characteristics of Zn_(1-x)TM_xTe(TM = Mn,Fe,Co,Ni and x = 6.25%),calculated through Wien2 k code,by using full potential linearized augmented plane wave(FP-LAPW) techn...We present structural,magnetic and optical characteristics of Zn_(1-x)TM_xTe(TM = Mn,Fe,Co,Ni and x = 6.25%),calculated through Wien2 k code,by using full potential linearized augmented plane wave(FP-LAPW) technique.The optimization of the crystal structures have been done to compare the ferromagnetic(FM) and antiferromagnetic(AFM) ground state energies,to elucidate the ferromagnetic phase stability,which further has been verified through the formation and cohesive energies.Moreover,the estimated Curie temperatures T_c have demonstrated above room temperature ferromagnetism(RTFM) in Zn_(1-x)TM_xTe(TM =Mn,Fe,Co,Ni and x= 6.25%).The calculated electronic properties have depicted that Mn- and Co-doped ZnTe behave as ferromagnetic semiconductors,while half-metallic ferromagnetic behaviors are observed in Fe- and Ni-doped ZnTe.The presence of ferromagnetism is also demonstrated to be due to both the p-d and s-d hybridizations between the host lattice cations and TM impurities.The calculated band gaps and static real dielectric constants have been observed to vary according to Penn's model.The evaluated band gaps lie in near visible and ultraviolet regions,which make these materials suitable for various important device applications in optoelectronic and spintronic.展开更多
We show how the traditional grid based method for finding neutrino oscillation parameters m2 and tan 2θ can be combined with an optimization technique,Differential Evolution(DE),to get a significant decrease in compu...We show how the traditional grid based method for finding neutrino oscillation parameters m2 and tan 2θ can be combined with an optimization technique,Differential Evolution(DE),to get a significant decrease in computer processing time required to obtain minimal chi-square(χ2) in four different regions of the parameter space.We demonstrate efficiency for the two-neutrinos case.For this,the χ2 function for neutrino oscillations is evaluated for grids with different density of points in standard allowed regions of the parameter space of m2 and tan 2θ using experimental and theoretical total event rates of chlorine(Homestake),Gallex+GNO,SAGE,Superkamiokande,and SNO detectors.We find that using DE in combination with the grid based method with small density of points can produce the results comparable with the one obtained using high density grid,in much lesser computation time.展开更多
For a system of current interest(composed of charm, anticharm and a pair of light quarks), we show trends in phenomenological implications of QCD-based improvements to a simple quark model treatment. We employ a res...For a system of current interest(composed of charm, anticharm and a pair of light quarks), we show trends in phenomenological implications of QCD-based improvements to a simple quark model treatment. We employ a resonating group method to render this difficult four-body problem manageable. We use a quadratic confinement so as to be able to improve beyond the Born approximation. We report the position of the pole corresponding to the D^0D^0* molecule for the best fit of a model parameter to the relevant QCD simulations. We point out the interesting possibility that the pole can be shifted to 3872 Me V by introducing another parameter I0 that changes the strength of the interaction in this one component of X(3872). The revised value of this second parameter can guide future trends in modeling of the full exotic meson X(3872). We also report the changes with I_0 in the S-wave spin averaged cross sections for D^0D^0*-→ωJ/ψ and D^0D^0*-→ρJ/ψ. These cross sections are important regarding the study of QGP(quark gluon plasma).展开更多
Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π+π- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π+π-)=(4.30±0.13±0...Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π+π- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π+π-)=(4.30±0.13±0.99)×10-3, excluding the decays to intermediate states, namely J/ψ→Ξ-Ξ+, J/ψ→Σ(1385)-Σ(1385)+, and J/ψ→Σ(1385)+Σ(1385)-. The branching fractions for these intermediate resonance channels are measured to be:Br(J/ψ→Ξ-Ξ+)=(0.90±0.03±0.18)×10-3, Br(J/ψ→Σ(1385)-Σ(1385)+)=(1.23±0.07±0.30)×10-3,and Br(J/ψ→Σ(1385)+Σ(1385)-)=(1.50±0.08±0.38)×10-3, respectively. The angular distribution is of the form dN/d(cosθ)α(1+αcos2θ) with α=(0.35±0.29±0.06) for J/ψ→Ξ-Ξ+, α=(-0.54±0.22±0.10) for J/ψ→Σ(1385)-Σ(1385)+, and α=(-0.35±0.29±0.06) for J/ψ→Σ(1385)+Σ(1385)-.展开更多
文摘Thermionic electron beam is a fundamental part of all types of linear accelerators around the world in the field of Experimental High Energy Physics. Thermionic beam is very inexpensive and simple to produce. In this work, we give an overview of generation, design and applications of the electron beam with particular reference to e-beam generation at high energy linear accelerators. Experimental data are presented in tabular form for ready reference. We also make an evaluation of these high energy sources with our in-house designed e-beam gun. Finally, a comparison has been presented in terms of characteristic parameters of all these high performance sources.
基金funded by the National Natural Science Foundation of China (Grant No. 11975145)
文摘This study aims to discuss anisotropic solutions that are spherically symmetric in the quintessence field,which describe compact stellar objects in the modified Rastall teleparallel theory of gravity.To achieve this goal,the Krori and Barua arrangement for spherically symmetric components of the line element is incorporated.We explore the field equations by selecting appropriate off-diagonal tetrad fields.Born-Infeld function of torsion f(T)=β√λT+1-1 and power law form h(T)=δTn are used.The Born-Infeld gravity was the first modified teleparallel gravity to discuss inflation.We use the linear equation of state pr=ξρto separate the quintessence density.After obtaining the field equations,we investigate different physical parameters that demonstrate the stability and physical acceptability of the stellar models.We use observational data,such as the mass and radius of the compact star candidates PSRJ 1416-2230,Cen X-3,&4U 1820-30,to ensure the physical plausibility of our findings.
基金the Deanship of Scientific Research at King Saud University for funding this Prolific Research Group (PRG-1436-26)
文摘The mechanical, electronic and magnetic properties of non-magnetic MgTe and ferro-magnetic (FM) Mgo.75 TM025 Te (TM = Fe, Co, Ni) in the zinc-blende phase are studied by ab-initio calculations for the first time. We use the generalized gradient approximation functional for computing the structural stability, and mechanical properties, while the modified Becke and Johnson local (spin) density approximation (mBJLDA) is utilized for determining the electronic and magnetic properties. By comparing the energies of non-magnetic and FM calculations, we find that the compounds are stable in the FM phase, which is confirmed by their structural stabilities in terms of enthalpy of formation. Detailed descriptions of elastic properties of Mgo.75TMo.25Te alloys in the FM phase are also presented. For electronic properties, the spin- polarized electronic band structures and density of states are computed, showing that these compounds are direct bandgap materials with strong hybridizations of TM 3d states and Te p states. Further, the ferromagnetism is discussed in terms of the Zener free electron model, RKKY model and double exchange model. The charge density contours in the (110) plane are calculated to study bonding properties. The spin exchange splitting and crystal field splitting energies are also calculated. The distribution of electron spin density is employed in computing the magnetic moments appearing at the magnetic sites (Fe, Co, Ni), as well as at the non-magnetic sites (Mg, Te). It is found that the p-d hybridization causes not only magnetic moments on the magnetic sites but also induces negligibly small magnetic moments at the non-magnetic sites.
文摘Free falling hypersurfaces in the Schwarzschild geometry have been studied to provide a complete foliation of spacetime. The hypersurfaces do not cross into the maximally extended spacetime and are well behaved everywhere except at the singularity r =0 the mean extrinsic curvature becomes infinity.
基金support of the National Natural Science Foundation of China(NSFC,Grant Nos.11822305,11773031 and 11633004)the Chinese Academy of Sciences(CAS)Strategic Priority Research Program(XDA15020200)+1 种基金the NSFC-ISF joint research program(No.11761141012)the CAS Interdisciplinary Innovation Team。
文摘Ultra-light axions(ULAs)with mass less than 10-20 eV have interesting behaviors that may contribute to either dark energy or dark matter at different epochs of the Universe.Their properties can be explored by cosmological observations,such as expansion history of the Universe,cosmic large-scale structure,cosmic microwave background,etc.In this work,we study the ULAs with mass around 10-33 eV,which means that the ULA field still rolls slowly at present with the equation of state w=-1 as dark energy.To investigate the mass and other properties of this kind of ULA field,we adopt the measurements of Type Ia supernova(SN Ia),baryon acoustic oscillation(BAO),and Hubble parameter H(z).The Markov Chain Monte Carlo(MCMC)technique is employed to perform the constraints on the parameters.Finally,by exploring four cases of the model,we find that the mass of this ULA field is about 3×10-33 eV if assuming the initial axion fieldφi=Mpl.We also investigate a general case by assumingφi≤Mpl,and find that the fitting results ofφi/Mpl are consistent with or close to 1 for the datasets that we use.
文摘Using theΣ-form factor it is shown that the Donnachie-Landshoff pomeron gives a good description of the high energy total and elastic differential cross-section data forΣ-p scattering.
文摘Most recent data for the differential cross section and polarisation for the hypercharge exchange reaction π+p → K+Σ+ and its line-reversed partners is explained by using the simple Regge pole model with phenomenological residue functions.
文摘The differential cross section data for high energy K-p elastic scattering showing a break near-t=4(Gev/c)^(2) have been fitted for pL=20,100 and 200GeV/c with-t extended up to 14(Gev/c)^(2) by using a dipole pomeron mode.
基金supported by the National Natural Science Foundation of China(Grant Nos.12135007 and 11805097)the Alexander von Humboldt Foundation+1 种基金and STRONG-2020“The strong interaction at the frontier of knowledge:fundamental research and applications”which received funding from the European Union’s Horizon 2020 research and innovation programme(Grant No.824093)。
文摘Beginning with precise data on the ratio of structure functions in deep inelastic scattering(DIS)from ^3He and ^3H,collected on the domain 0.19≤xB≤0.83,where xBis the Bjorken scaling variable,we employ a robust method for extrapolating such data to arrive at a model-independent result for the xB=1 value of the ratio of neutron and proton structure functions.Combining this with information obtained in analyses of DIS from nuclei,corrected for target-structure dependence,we arrive at a prediction for the proton valence-quark ratio:d_(v)/u_(v)|_(xB→1)=0.230(57).Requiring consistency with this result presents a challenge to many descriptions of proton structure.
文摘The mass concentrations of eighteen airborne samples collected from Lahore (Pakistan) are found in the range from 595 to 3027μg/m3with average value of 1130 μg/m3. Most of these values are normal and as reported in the literature for other parts of the world. The major phases identified in the samples by the X-ray powder diffraction technique are Albite (Anorthite), Calcite, Clinochlore (Chlorite), Gypsum, Illite, Quartz and Talc which have also been reported by other researchers to be present in the airborne particulates of other world locations. The average weight percentages of the phases (minerals) in the samples are respectively 15.5, 10.6, 23.7, 2.4, 19.1, 20.2, and 8.5. Some of the elements (e.g., boron, cadmium, lithium, manganese, titanium, and zinc) quantified in two samples determined using a spark-source mass spectrometer appear also to derive their origin from man-made activities. However no compound synthesized in the atmosphere is detected by the X-ray diffraction method.
基金the University of the Punjab, Lahore for financial support through faculty research grant program
文摘We present structural,magnetic and optical characteristics of Zn_(1-x)TM_xTe(TM = Mn,Fe,Co,Ni and x = 6.25%),calculated through Wien2 k code,by using full potential linearized augmented plane wave(FP-LAPW) technique.The optimization of the crystal structures have been done to compare the ferromagnetic(FM) and antiferromagnetic(AFM) ground state energies,to elucidate the ferromagnetic phase stability,which further has been verified through the formation and cohesive energies.Moreover,the estimated Curie temperatures T_c have demonstrated above room temperature ferromagnetism(RTFM) in Zn_(1-x)TM_xTe(TM =Mn,Fe,Co,Ni and x= 6.25%).The calculated electronic properties have depicted that Mn- and Co-doped ZnTe behave as ferromagnetic semiconductors,while half-metallic ferromagnetic behaviors are observed in Fe- and Ni-doped ZnTe.The presence of ferromagnetism is also demonstrated to be due to both the p-d and s-d hybridizations between the host lattice cations and TM impurities.The calculated band gaps and static real dielectric constants have been observed to vary according to Penn's model.The evaluated band gaps lie in near visible and ultraviolet regions,which make these materials suitable for various important device applications in optoelectronic and spintronic.
基金the Higher Education Commission(HEC) of Pakistan for its financial support through Grant No.17-5-2(Ps2-044) HEC/Sch/2004
文摘We show how the traditional grid based method for finding neutrino oscillation parameters m2 and tan 2θ can be combined with an optimization technique,Differential Evolution(DE),to get a significant decrease in computer processing time required to obtain minimal chi-square(χ2) in four different regions of the parameter space.We demonstrate efficiency for the two-neutrinos case.For this,the χ2 function for neutrino oscillations is evaluated for grids with different density of points in standard allowed regions of the parameter space of m2 and tan 2θ using experimental and theoretical total event rates of chlorine(Homestake),Gallex+GNO,SAGE,Superkamiokande,and SNO detectors.We find that using DE in combination with the grid based method with small density of points can produce the results comparable with the one obtained using high density grid,in much lesser computation time.
基金support of PU research (D/605/Est.I Sr. 20 Project 2014-15, D/34/Est.1 Sr. 109 Project 2013-14)the Higher Education Commission (HEC) of Pakistan for its financial support through (17-5-4(Ps3-128) HEC/Sch/2006)
文摘For a system of current interest(composed of charm, anticharm and a pair of light quarks), we show trends in phenomenological implications of QCD-based improvements to a simple quark model treatment. We employ a resonating group method to render this difficult four-body problem manageable. We use a quadratic confinement so as to be able to improve beyond the Born approximation. We report the position of the pole corresponding to the D^0D^0* molecule for the best fit of a model parameter to the relevant QCD simulations. We point out the interesting possibility that the pole can be shifted to 3872 Me V by introducing another parameter I0 that changes the strength of the interaction in this one component of X(3872). The revised value of this second parameter can guide future trends in modeling of the full exotic meson X(3872). We also report the changes with I_0 in the S-wave spin averaged cross sections for D^0D^0*-→ωJ/ψ and D^0D^0*-→ρJ/ψ. These cross sections are important regarding the study of QGP(quark gluon plasma).
基金Supported by National Natural Science Foundation of China(10491300,10225524,10225525,10425523,10625524,10521003,10821063,10825524)Chinese Academy of Sciences(KJ95T-03)+3 种基金100Talents Program of CAS(U-11,U-24,U-25)Knowledge Innovation Project of CAS(U-602,U-34)(IHEP)National Natural Science Foundation of China(10775077,10225522)(Tsinghua University)Department of Energy(DE-FG02-04ER41291)(U.Hawaii)
文摘Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π+π- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π+π-)=(4.30±0.13±0.99)×10-3, excluding the decays to intermediate states, namely J/ψ→Ξ-Ξ+, J/ψ→Σ(1385)-Σ(1385)+, and J/ψ→Σ(1385)+Σ(1385)-. The branching fractions for these intermediate resonance channels are measured to be:Br(J/ψ→Ξ-Ξ+)=(0.90±0.03±0.18)×10-3, Br(J/ψ→Σ(1385)-Σ(1385)+)=(1.23±0.07±0.30)×10-3,and Br(J/ψ→Σ(1385)+Σ(1385)-)=(1.50±0.08±0.38)×10-3, respectively. The angular distribution is of the form dN/d(cosθ)α(1+αcos2θ) with α=(0.35±0.29±0.06) for J/ψ→Ξ-Ξ+, α=(-0.54±0.22±0.10) for J/ψ→Σ(1385)-Σ(1385)+, and α=(-0.35±0.29±0.06) for J/ψ→Σ(1385)+Σ(1385)-.