Physics Letters B 797 (2019) 134890 We report the first measurement of the $(e,e'p)$ reaction cross-section
ratios for Helium-3 ($^3$He), Tritium ($^3$H), and Deuterium ($d$). The
measurement covered ...a missing momentum range of $40 \le p_{miss} \le 550$
MeV$/c$, at large momentum transfer ($\langle Q^2 \rangle \approx 1.9$
(GeV$/c$)$^2$) and $x_B>1$, which minimized contributions from non
quasi-elastic (QE) reaction mechanisms. The data is compared with plane-wave
impulse approximation (PWIA) calculations using realistic spectral functions
and momentum distributions. The measured and PWIA-calculated cross-section
ratios for $^3$He$/d$ and $^3$H$/d$ extend to just above the typical nucleon
Fermi-momentum ($k_F \approx 250$ MeV$/c$) and differ from each other by $\sim
20\%$, while for $^3$He/$^3$H they agree within the measurement accuracy of
about 3\%. At momenta above $k_F$, the measured $^3$He/$^3$H ratios differ from
the calculation by $20\% - 50\%$. Final state interaction (FSI) calculations
using the generalized Eikonal Approximation indicate that FSI should change the
$^3$He/$^3$H cross-section ratio for this measurement by less than 5\%. If
these calculations are correct, then the differences at large missing momenta
between the $^3$He/$^3$H experimental and calculated ratios could be due to the
underlying $NN$ interaction, and thus could provide new constraints on the
previously loosely-constrained short-distance parts of the $NN$ interaction.
The proton is composed of quarks and gluons, bound by the most elusive mechanism of strong interaction called confinement. In this work, the dynamics of quarks and gluons are investigated using ...deeply virtual Compton scattering (DVCS): produced by a multi-GeV electron, a highly virtual photon scatters off the proton which subsequently radiates a high energy photon. Similarly to holography, measuring not only the magnitude but also the phase of the DVCS amplitude allows to perform 3D images of the internal structure of the proton. The phase is made accessible through the quantum-mechanical interference of DVCS with the Bethe-Heitler (BH) process, in which the final photon is emitted by the electron rather than the proton. We report herein the first full determination of the BH-DVCS interference by exploiting the distinct energy dependences of the DVCS and BH amplitudes. In the high energy regime where the scattering process is expected to occur off a single quark in the proton, these accurate measurements show an intriguing sensitivity to gluons, the carriers of the strong interaction.
Phys. Rev. Lett. 118, 222002 (2017) We report the first longitudinal/transverse separation of the deeply virtual
exclusive $\pi^0$ electroproduction cross section off the neutron and coherent
...deuteron. The corresponding four structure functions $d\sigma_L/dt$,
$d\sigma_T/dt$, $d\sigma_{LT}/dt$ and $d\sigma_{TT}/dt$ are extracted as a
function of the momentum transfer to the recoil system at $Q^2$=1.75 GeV$^2$
and $x_B$=0.36. The $ed \to ed\pi^0$ cross sections are found compatible with
the small values expected from theoretical models. The $en \to en\pi^0$ cross
sections show a dominance from the response to transversely polarized photons,
and are in good agreement with calculations based on the transversity GPDs of
the nucleon. By combining these results with previous measurements of $\pi^0$
electroproduction off the proton, we present a flavor decomposition of the $u$
and $d$ quark contributions to the cross section.
Phys. Rev. Lett. 117, 262001 (2016) We present deeply virtual $\pi^0$ electroproduction cross-section
measurements at $x_B$=0.36 and three different $Q^2$--values ranging from 1.5
to 2 GeV$^2$, ...obtained from experiment E07-007 that ran in the Hall A at
Jefferson Lab. The Rosenbluth technique was used to separate the longitudinal
and transverse responses. Results demonstrate that the cross section is
dominated by its transverse component, and thus is far from the asymptotic
limit predicted by perturbative Quantum Chromodynamics. An indication of a
non-zero longitudinal contribution is provided by the interference term
$\sigma_{LT}$ also measured. Results are compared with several models based on
the leading twist approach of Generalized Parton Distributions (GPDs). In
particular, a fair agreement is obtained with models where the scattering
amplitude is described by a convolution of chiral-odd (transversity) GPDs of
the nucleon with the twist-3 pion distribution amplitude. Therefore, neutral
pion electroproduction may offer the exciting possibility of accessing
transversity GPDs through experiment.
We report the first measurement of the \((e,e'p)\) reaction cross-section ratios for Helium-3 (\(^3\)He), Tritium (\(^3\)H), and Deuterium (\(d\)). The measurement covered a missing momentum range of ...\(40 \le p_{miss} \le 550\) MeV\(/c\), at large momentum transfer (\(\langle Q^2 \rangle \approx 1.9\) (GeV\(/c\))\(^2\)) and \(x_B>1\), which minimized contributions from non quasi-elastic (QE) reaction mechanisms. The data is compared with plane-wave impulse approximation (PWIA) calculations using realistic spectral functions and momentum distributions. The measured and PWIA-calculated cross-section ratios for \(^3\)He\(/d\) and \(^3\)H\(/d\) extend to just above the typical nucleon Fermi-momentum (\(k_F \approx 250\) MeV\(/c\)) and differ from each other by \(\sim 20\%\), while for \(^3\)He/\(^3\)H they agree within the measurement accuracy of about 3\%. At momenta above \(k_F\), the measured \(^3\)He/\(^3\)H ratios differ from the calculation by \(20\% - 50\%\). Final state interaction (FSI) calculations using the generalized Eikonal Approximation indicate that FSI should change the \(^3\)He/\(^3\)H cross-section ratio for this measurement by less than 5\%. If these calculations are correct, then the differences at large missing momenta between the \(^3\)He/\(^3\)H experimental and calculated ratios could be due to the underlying \(NN\) interaction, and thus could provide new constraints on the previously loosely-constrained short-distance parts of the \(NN\) interaction.
We report the first longitudinal/transverse separation of the deeply virtual exclusive \(\pi^0\) electroproduction cross section off the neutron and coherent deuteron. The corresponding four ...structure functions \(d\sigma_L/dt\), \(d\sigma_T/dt\), \(d\sigma_{LT}/dt\) and \(d\sigma_{TT}/dt\) are extracted as a function of the momentum transfer to the recoil system at \(Q^2\)=1.75 GeV\(^2\) and \(x_B\)=0.36. The \(ed \to ed\pi^0\) cross sections are found compatible with the small values expected from theoretical models. The \(en \to en\pi^0\) cross sections show a dominance from the response to transversely polarized photons, and are in good agreement with calculations based on the transversity GPDs of the nucleon. By combining these results with previous measurements of \(\pi^0\) electroproduction off the proton, we present a flavor decomposition of the \(u\) and \(d\) quark contributions to the cross section.
We present deeply virtual \(\pi^0\) electroproduction cross-section measurements at \(x_B\)=0.36 and three different \(Q^2\)--values ranging from 1.5 to 2 GeV\(^2\), obtained from experiment E07-007 ...that ran in the Hall A at Jefferson Lab. The Rosenbluth technique was used to separate the longitudinal and transverse responses. Results demonstrate that the cross section is dominated by its transverse component, and thus is far from the asymptotic limit predicted by perturbative Quantum Chromodynamics. An indication of a non-zero longitudinal contribution is provided by the interference term \(\sigma_{LT}\) also measured. Results are compared with several models based on the leading twist approach of Generalized Parton Distributions (GPDs). In particular, a fair agreement is obtained with models where the scattering amplitude is described by a convolution of chiral-odd (transversity) GPDs of the nucleon with the twist-3 pion distribution amplitude. Therefore, neutral pion electroproduction may offer the exciting possibility of accessing transversity GPDs through experiment.
Epigenetic changes including DNA and histone methylation may reorganise the nuclear architecture during in vitro culture. The states of methylation resulting from in vitro cultures are often related ...to control the somatic embryogenesis and regeneration process via modulating gene expression. By changing the methylation profile, it is possible to alter gene expression which may be applicable to produce large number of high quality planting materials or to improve agronomic traits leading to crop improvement. Understanding the molecular mechanisms of methylation alterations and acquisition of developmental cell fate during in vitro cultures can help in the development of strategies to enhance the embryogenic capability and totipotency in recalcitrant plant species and genotypes. Moreover, the methylation profile may also be useful to adapt crops under adverse environment as the plants undergo through various stresses during in vitro cultures. In this article, we review the literature on the role of DNA and histone methylation in plant variation and discuss the potential of targeted epigenetic variation for crop improvement.
Energy insufficiency is obstructing the socio-economic and industrial improvement of Bangladesh. Renewable energy contributes about 560 Megawatt (MW) of the total electricity production of 20,430 MW, ...which can be a sustainable solution to the demand-supply crisis. This paper, summarises the current energy situation of Bangladesh and examines the available renewable energy resources and their future prospect. It has been revealed that Bangladesh is heavily (62%) relying on natural gas although government has already taken steps to generate electricity from renewable energy sources. Current policies and legislations related to generation of renewable energy in Bangladesh have been discussed explicitly. Finally, some suggestions have been made to tackle the ongoing energy crisis in the country, in addition to the renewable energy.Abbreviations: GDP: Gross domestic product; RNPP: Rooppur Nuclear Power Plant; Tcf: Trillion cubic feet; IDCOL: Infrastructure development company limited; BPDB: Bangladesh Power Development Board: GS: Grameen Shakti; BWDB: Bangladesh Water Development Board: USD: United States Dollar; IPP: Independent power producer: BCAS: Bangladesh center for advanced studies; NWPGCL: North West Power Generation Company Limited: BCSIR: Bangladesh Council of Scientific and Industrial Research; EGCB: Electricity Generation Company of Bangladesh: WRA: Wind Resource Assessment; REB: Rural Electrification Board: BRAC: Bangladesh Rural Advancement Committee; kW: Kilowatt: PJ: Petajoules; MW: Megawatt: IFRAD: Institute for fuel research and Development; GWh: Gigawatt hours: ICS: Improved Cooking Stoves; MWh: Megawatt hours: DoE: Department of Environment; TWh: Trillion-watt hour: DLS: Department of Livestock Services; RPCL: Rural Power Company Limited: mmcfd: million cubic feet per day; APSCL: Ashugang Power Station Company Limited: BSCIC: Bangladesh Small & Cottage Industries Corporation (BSCIC); GOB: Government of Bangladesh: BADC: Bangladesh Agricultural Development Corporation; SREDA: Sustainable and Renewable Energy Development Authority: DIDA: Danish International Development Agency; LGED: Local Government Engineering Directorate: BAU: Bangladesh Agricultural University; NGO: Non-Governmental Organization: HBRI: Housing & Building Research Institute; IRENA: International Renewable energy Agency: : BARD: Bangladesh Academy for Rural Development; ETP: Electronic Traffic Pricing: BCCD: Bangladesh Commission for Christian Development; PV: Photovoltaic: BRRI: Bangladesh Rice Research Institute; SHS: Solar Home Systems: NDBMP: National Domestic Biogas and Manure Program; TOE: Tonne of oil equivalent: K/km: Kelvin/kilometer; LEAP: Long range Energy Alternative Planning
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