Ratio Of Differential Cross Sections Research Articles

Atomic mass, Bjorken variable, and scale dependence of quark transport coefficient in Drell-Yan process for proton incident on nucleus* *Supported in part by the National Natural Science Foundation of China (11975090, 11575052).

By means of the nuclear parton distributions determined without the fixed-target Drell-Yan experimental data and the analytic expression of quenching weight based on the BDMPS formalism, next-to-leading order analyses were performed on the Drell-Yan differential cross section ratios from the Fermilab E906 and E866 collaborations. It was found that the results calculated only with the nuclear effects of the parton distribution were not in agreement with the E866 and E906 experimental data. The incoming parton energy loss effect cannot be ignored in the nuclear Drell-Yan reactions. The predicted results indicate that, with the quark transport coefficient as a constant, the suppression due to the target nuclear geometry effect is approximately% for the quark transport coefficient. It was shown that we should consider the target nuclear geometry effect in studying the Drell-Yan reaction on nuclear targets. On the basis of the Bjorken variable and scale dependence of the quark transport coefficient, the atomic mass dependence was incorporated. The quark transport coefficient was determined as a function of the atomic mass, Bjorken variable, and scale by the global fit of the experimental data. The determined constant factor of the quark transport coefficient is GeV/fm. It was found that the atomic mass dependence has a significant impact on the constant factor in the quark transport coefficient in cold nuclear matter.

Investigation of coherent/Compton scattering differential cross section ratios in Cu alloys as depending on chemical environment and scattering angle

In this study, seven alloys with a nominal composition of (CuO2)0.5 M0.5 (M = Fe, Co, Ni, Cu, Zn, Y, and Nb wt%) were produced via the powder mixed method. Alloys and pure metals were excited with 59.54 keV photon energy emitted from Am-241 radioactive source at 25°, 35°, 45°, 55°, 65°, 75′ and 85° scattering angles. The spectra of the coherent/Compton peaks were obtained by Si(Li) detector. First of all, chemical shift, (ΔE) peak energies, (E) asymmetry index (As) and full width half maximum (FWHM) values were found in the Compton/Coherent scattering spectra obtained depending on the scattering angle and the chemical environment of the transition metals. Then the ratios of the Coherent/Compton scattering differential cross-section (dσcoherent/dσCompton) were obtained experimentally. The experimental dσcoherent/dσCompton ratios of the selected 3d-4d transition metals were found to be compatible with the data in the literature. Asymmetry and chemical shifts were observed in almost all samples, especially in Compton peaks, with increasing scattering angles. The chemical shifts of Compton and Coherent peaks of the alloys were found in the range of 1–932 eV. The experimental dσkoherent/dσCompton ratios for the alloys obtained by adding Fe, Co, Ni, Cu, Zn, Y, and Nb to Cu2O were found as 0.697, 0.689 0.678, 0.698, 0.736, 0.755, 0.798, 0.835 at 45° scattering angle, respectively. It has been determined that the experimental dσcoherent/dσCompton ratio for each alloy increases with increasing atomic number, while it decreases with increasing scattering angle.

Nuclear effects in neutrino-nucleus DIS and a probe for short-range correlations

We investigate charged-current neutrino-nucleus deep inelastic scattering with particular interests in relationship of short range correlation (SRC) and EMC effect. The structure functions $F^A_2(x,Q^2)$, $x F^A_3(x,Q^2)$ and ratios of differential cross sections are presented where the nuclei $A$ are chosen to be carbon, iron and lead. We propose a kind of universal modification functions which would provide a nontrivial test of SRC universality on the platform of neutrino-nucleus scattering and improve our understanding of nucleon structure substantially.

Bjorken variable and scale dependence of quark transport coefficient in Drell–Yan process for proton incident on nucleus

The Drell-Yan process for proton incident on nuclei is an excellent place for deeply studying the parton propagation in a nucleus. By means of the nuclear parton distributions determined only with lepton-nuclear deep inelastic scattering experimental data and the analytic parameterization of quenching weight based on BDMPS formalism, a phenomenological analysis of the nuclear Drell-Yan differential cross section ratio as a function of Feynman variable is performed from Fermilab E906 and E866 experimental data. With the nuclear geometry effect on nuclear Drell-Yan process and the quark transport coefficient as a constant, our predictions are in good agreement with the experimental measurements. It is found that nuclear geometry effect has a significant impact on the quark transport coefficient in cold nuclear matter. It is necessary to consider the detailed nuclear geometry in studying the nuclear Drell-Yan process. Our calculated results reveal that the difference in the values of quark transport coefficient exists from E906 and E866 experiments. However, confirming the conclusion that the quark transport coefficient depends on the target-quark momentum fraction, still need more accurate experimental data on the Drell-Yan differential cross section ratio in the future. Three models are proposed and discussed for the quark transport coefficient as a function of the measurable kinematic variables. The quark transport coefficient $\hat{q}$ is determined as a function of the Bjorken variable $x_2$ and scale $Q^2$. It is hoped that the parametrization form of quark transport coefficient in the cold nuclear medium can help to think about the parton propagation mechanism in nuclear matter.

Prediction of the analyzing power for p⃗+He6 elastic scattering at 200 MeV from p⃗+He4 elastic scattering at 200 MeV

We apply the cluster-folding (CF) model for $\vec{p}+^{6}$He scattering at 200 MeV, where the potential between $\vec{p}$ and $^{4}$He is fitted to data on $\vec{p}+^{4}$He scattering at 200 MeV. For $\vec{p}+^{6}$He scattering at 200 MeV, the CF model reproduces measured differential cross section with no free parameter, We then predict the analyzing power $A_y(q)$ with the CF model, where $q$ is the transfer momentum. Johnson, Al-Khalili and Tostevin construct a theory for one-neutron halo scattering, taking (1) the adiabatic approximation and (2) neglecting the interaction between a valence neutron and a target, and yield a simple relationship between the elastic scattering of a halo nucleus and of its core under certain conditions. We improve their theory with (3) the eikonal approximation in order to determine $A_y(q)$ for $^{6}$He from the data on $A_y(q)$ for $^{4}$He. The improved theory is accurate, when approximation (1)--(3) are good. Among the three approximations, approximation (2) is most essential. The CF model shows that approximation (2) is good in $0.9 < q < 2.4$ fm$^{-1}$. In the improved theory, the $A_y(q)$ for $^{6}$He is the same as that for $^{4}$He. In $0.9 < q < 2.4$ fm$^{-1}$, we then predict $A_y(q)$ for $\vec{p}+^{6}$He scattering at 200 MeV from measured $A_y(q)$ for $\vec{p}+^{4}$He scattering at 200 MeV. We thus predict $A_y(q)$ with the model-dependent and the model-independent prescription. The ratio of differential cross sections measured for $^{6}$He to that for $^{4}$He is related to the wave function of $^{6}$He. We then determine the radius between $^{4}$He and the center-of-mass of valence two neutrons in $^{6}$He. The radius is 5.77 fm.

Drell-Yan nuclear modification due to nuclear effects of nPDFs and initial-state parton energy loss * *Supported partially by National Natural Science Foundation of China (11405043), Natural Science Foundation of Hebei Province (A2018209269) and Science and Technology Foundation of Hebei Education Department (ZD2020104)

By globally analyzing nuclear Drell-Yan data including all incident energies, the nuclear effects of nuclear parton distribution functions (nPDFs) and initial-state parton energy loss are investigated. Based on the Landau-Pomeranchuk-Migdal (LPM) regime, the calculations are carried out by means of analytic parametrizations of quenching weights derived from the Baier-Dokshitzer-Mueller-Peign -Schiff (BDMPS) formalism and using the new EPPS16 nPDFs. It is found that the results are in good agreement with the data and the role of the energy loss effect in the suppression of Drell-Yan ratios is prominent, especially for low-mass Drell-Yan measurements. The nuclear effects of nPDFs become more obvious with increasing nuclear mass number A, the same as the energy loss effect. By a global fit, the transport coefficient extracted is GeV2/fm. In addition, to avoid diminishing the QCD NLO correction to the data form of Drell-Yan ratios, separate calculations of the Compton differential cross section ratios at 120 GeV are performed, which provides a feasible way to better distinguish the gluon energy loss in Compton scattering. It is found that the role of the initial-state gluon energy loss in the suppression of Compton scattering ratios is not very important and disappears with the increase of .

Measurement of the associated production of a Z boson with charm or bottom quark jets in proton-proton collisions at s=13 TeV

Ratios of cross sections, $\sigma$(Z+c jets) / $\sigma$(Z+jets), $\sigma$(Z+b jets) / $\sigma$(Z+jets), and $\sigma$(Z+c jets) / $\sigma$(Z+b jets) in the associated production of a Z boson with at least one charm or bottom quark jet are measured in proton-proton collisions at $\sqrt{s} =$ 13 TeV. The data sample, collected by the CMS experiment at the CERN LHC, corresponds to an integrated luminosity of 35.9 fb$^{-1}$, with a fiducial volume of $p_\mathrm{T}$ $>$ 30 GeV and $|\eta|$ $<$ 2.4 for the jets, where $p_\mathrm{T}$ and $\eta$ represent transverse momentum and pseudorapidity, respectively. The Z boson candidates come from leptonic decays into electrons or muons with $p_\mathrm{T}$ $>$ 25 GeV and $|\eta|$ $<$ 2.4, and the dilepton mass satisfies 71 $\lt$ $m_\mathrm{Z}$ $\lt$ 111 GeV. The measured values are $\sigma$(Z+c jets) / $\sigma$(Z+jets) = 0.102 $\pm$ 0.002 $\pm$ 0.009, $\sigma$(Z+b jets) / $\sigma$(Z+jets) = 0.0633 $\pm$ 0.0004 $\pm$ 0.0015, and $\sigma$(Z+c jets) / $\sigma$(Z+b jets) = 1.62 $\pm$ 0.03 $\pm$ 0.15. Results on the inclusive and differential cross section ratios as functions of jet and Z boson transverse momentum are compared with predictions from leading and next-to-leading order perturbative quantum chromodynamics calculations. These are the first measurements of the cross section ratios at 13 TeV.

On Laser-Modified Rutherford Scattering

We present a theoretical analysis of a charged-particle scattering by a Coulomb potential in the presence of laser radiation. The effect of a laser field is studied using our recently developed nonperturbative parabolic quasi-Sturmian approach for solving the system of coupled Lippmann–Schwinger–Floquet equations in the Kramers–Henneberger frame. We calculate the ratio of multiphoton differential cross sections to the Rutherford cross section in the case of a laser-assisted electron-proton scattering process. Our results are compared with predictions of the Bunkin–Fedorov, Kroll–Watson, and Coulomb–Volkov analytical approximations: marked discrepancies are found for different net numbers of exchanged photons and different orientations of the laser-field polarization vector. Our findings clearly demonstrate deficiencies of those well-known approximations for describing laser-modified Rutherford scattering processes.

The study of the incoming parton energy loss effect on the NLO nuclear Drell–Yan ratios

At a next-to-leading order (NLO) calculation, the initial-state energy loss of the quark is investigated by means of the Drell–Yan experimental data including the new E906 measurements. Furthermore, the incoming gluon energy loss effect embedded in the Compton scattering subprocess of the nuclear Drell–Yan process is also examined. The NLO computations for Drell–Yan ratios are carried out with the SW quenching weights (provided by Salgado and Wiedemann to evaluate the probability distribution that quark (gluon) loses the energy), as well as the nuclear parton distributions (obtained by only fitting the existing experimental data on nuclear structure functions). It is found that the obtained calculations that consider the incoming quark energy loss agree well with the experimental data particularly for E906 data. In addition, the incoming gluon energy loss embodied in the primary NLO Compton scattering subprocess is not obvious, which may be due to the form of the Drell–Yan differential cross section ratio as a function of the quark momentum fraction () minimizes the influence of the QCD NLO correction.

The effect of external magnetic field on the coherent to Compton scattering differential cross section ratios of elements in the range 20 ≤ Z ≤ 32

The coherent to Compton differential cross section ratios were calculated for elements in the range 20 ≤ Z ≤ 32 under an external magnetic field. The elements were irradiated by 59.54 keV gamma rays from an 241Am radioactive source. A Si(Li) detector was used to detect the scattered photons. It was observed that the coherent to Compton differential cross section ratios of the samples increase with the magnetic field (B = 0, 0.4, and 0.8 T). The theoretical results were obtained with two different methods and compared with the experimental results at 0 T.

Measurement of the total neutron-scattering cross-section ratios of noble gases of natural isotopic composition using a pulsed neutron beam

Precision measurements of slow neutron cross sections with atoms have several scientific applications. In particular the n-$^{4}$He s-wave scattering length is important to know both for helping to constrain the nuclear three-body interaction and for the proper interpretation of several ongoing slow neutron experiments searching for other types of neutron-atom interactions. We present new measurements of the ratios of the neutron differential scattering cross sections for natural isotopic-abundance mixtures of the noble gases He, Ar, Kr, and Xe to natural isotopic abundance Ne. These measurements were performed using a recently developed neutron scattering apparatus for gas samples located on a pulsed slow neutron beamline which was designed to search for possible exotic neutron-atom interactions and employs both neutron time of flight information and a position-sensitive neutron detector for scattering event reconstruction. We found agreement with the literature values of scattering cross sections inferred from Ar/Ne, Kr/Ne and Xe/Ne differential cross section ratios over the $q$ range of $1 - 7$ nm$^{-1}$. However for the case of He/Ne we find that the cross section inferred differs by 11.3% (7.6 $\sigma$) from previously-reported values inferred from neutron phase shift measurements, but is in reasonable agreement with values from other measurements. The very large discrepancy in the He/Ne ratio calls for a new precision measurement of the n-$^{4}$He scattering length using neutron interferometry.

The coherent to Compton scattering differential cross section ratios of some fifth period elements in the external magnetic field

Some fifth-period elements Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag and Cd have been obtained in powder form and converted into pellets by applying pressure (~ 1 GPa). They have annealed at 1000 °C (except Cd ~ 300 °C). In the external magnetic fields (0.4 and 0.8 T) and without magnetic field, the coherent to Compton differential cross-sectional ratios has been investigated by using energy-dispersive X-ray fluorescence system. The data were analyzed via Origin 9.0 computer program. The results were calculated experimentally and theoretically. The theoretical results were obtained with two different methods, and these results were compared with the experimental results. These methods are relativistic form factor theory and non-relativistic form factor theory at without magnetic field. It was seen that the coherent to Compton differential cross-sectional ratios of the elements used in the present study increases with the increasing of the magnetic field and atomic number.

QCD analysis of CMS W + charm measurements at LHC with and implications for strange PDF * * Supported by the National Natural Science Foundation of China (11965020)

We calculate cross-sections and cross-section ratios of a charm quark production in association with a W gauge boson at next-to-leading order QCD using MadGraph and CT10NNLO, CT14NNLO, and MSTW2008NNLO PDFs. We compare the results with measurements from the CMS detector at the LHC at a center-of-mass energy of 7 TeV. Moreover, we calculate absolute and normalized differential cross-sections as well as differential cross-section ratios as a function of the lepton pseudorapidity from the W boson decay. The correlation between the CT14NNLO PDFs and predictions for charm data are studied as well. Furthermore, by employing the error PDF updating method proposed by the CTEQ-TEA group, we update CT14NNLO PDFs, and analyze the impact of CMS 7 TeV charm production data to the original CT14NNLO PDFs. By comparison of the , , , , , and PDFs at GeV and GeV for the CT14NNLO and CT14NNLO+Wc, we see that the error band of the PDF is reduced in the region , and the error band of PDF is also slightly reduced at region .

Elastic differential cross-section measurement at sqrt{s}=13\xa0TeV by TOTEM

The TOTEM collaboration has measured the elastic proton-proton differential cross section mathrm{d}sigma /mathrm{d}t at sqrt{s}=13 TeV LHC energy using dedicated beta ^{*}=90 m beam optics. The Roman Pot detectors were inserted to 10sigma distance from the LHC beam, which allowed the measurement of the range [0.04 GeV^{2}; 4 GeV^{2}] in four-momentum transfer squared |t|. The efficient data acquisition allowed to collect about 10^{9} elastic events to precisely measure the differential cross-section including the diffractive minimum (dip), the subsequent maximum (bump) and the large-|t| tail. The average nuclear slope has been found to be B=(20.40 pm 0.002^{mathrm{stat}} pm 0.01^{mathrm{syst}})~GeV^{-2} in the |t|-range 0.04–0.2 GeV^{2}. The dip position is |t_{mathrm{dip}}|=(0.47 pm 0.004^{mathrm{stat}} pm 0.01^{mathrm{syst}})~GeV^{2}. The differential cross section ratio at the bump vs. at the dip R=1.77pm 0.01^{mathrm{stat}} has been measured with high precision. The series of TOTEM elastic pp measurements show that the dip is a permanent feature of the pp differential cross-section at the TeV scale.

Measurement of coherent to Compton scattering differential cross-section ratios of cadmium at different momentum transfer factors

The coherent to Compton scattering ratio is a useful technique because it is independent of the density of the material and the material is defined only by the atomic number. Also, this ratio is used where changes in the atomic number are important and changes in the attenuation coefficient are too small to detect. In this study, coherent to Compton scattering ratios of cadmium have been calculated at different scattering angles (90°, 95°, 100°, 105°, 110°, 115°, 120°, 125°, and 130°). A high purity germanium detector was used. The coherent to Compton scattering differential cross-section ratios were plotted as a function of the scattering angles and constituted a best fit curve. It was observed that the coherent to Compton differential cross-section ratios decrease with an increasing scattering angle. The experimental results agree well with the results of the non-relativistic and relativistic form factor method.

Angular dependence of L X-rays of samarium, hafnium, and lead

Samarium, hafnium, and lead have great importance in making various absorbent materials. The L X-ray differential cross-sections of samarium, hafnium, and lead were measured within the range of with steps of 10° at 59.54 kiloelectron volt (keV) photon energy. In this study, angular dependence of L X-rays is explained by differential cross-section and intensity ratio calculations. The X-rays were found depend on the scattering angles weakly; therefore, we found reasonable to give the ratio to the X-rays. The anisotropy observed in the and X-rays but is not observed in and X-rays.

Variation of coherent to Compton scattering differential cross-section ratios of some lanthanides with the external magnetic field at 59.54 keV

Abstract The coherent to Compton differential cross-section ratios of some lanthanides have been calculated in an external magnetic field. The lanthanide samples were irritated by 59.54 keV from Am241 radioactive source. A Si(Li) detector was used for detected scattered photons. It was observed that the coherent to Compton differential cross-section ratios increase with increasing magnetic field (B = 0.4 T and 0.8 T). The coherent to Compton scattering differential cross-section ratios, corrected for photo-peak efficiency of gamma detector and absorption of photons in the sample and air. The obtained intensity ratios are plotted as function of the atomic number and constituted a best-fit-curve. The correlation coefficients for fit curves were found. The theoretical results were obtained with three different methods and compared with experimental results in 0 T.

Precise predictions for toverline{t}gamma /toverline{t} cross section ratios at the LHC

With the goal of increasing the precision of NLO QCD predictions for the ppto toverline{t}gamma process in the di-lepton top quark decay channel we present theoretical predictions for the mathrm{mathcal{R}}={sigma}_{toverline{t}gamma }/{sigma}_{toverline{t}} cross section ratio. Results for the latter together with various differential cross section ratios are given for the LHC with the Run II energy of sqrt{s}=13 TeV. Fully realistic NLO computations for toverline{t} and toverline{t}gamma production are employed. They are based on matrix elements for {e}^{+}{nu}_e{mu}^{-}{overline{nu}}_{mu }boverline{b} and {e}^{+}{nu}_e{mu}^{-}{overline{nu}}_{mu }boverline{b}gamma processes and include all resonant and non-resonant diagrams, interferences, and off-shell effects of the top quarks and the W gauge bosons. Various renormalisation and factorisation scale choices and parton density functions are examined to assess their impact on the cross section ratio. Depending on the transverse momentum cut on the hard photon a judicious choice of a dynamical scale allows us to obtain 1%–3% percent precision on mathrm{mathcal{R}} . Moreover, for differential cross section ratios theoretical uncertainties in the range of 1%-6% have been estimated. Until now such high precision predictions have only been reserved for the top quark pair production at NNLO QCD. Thus, mathrm{mathcal{R}} at NLO in QCD represents a very precise observable to be measured at the LHC for example to study the top quark charge asymmetry or to probe the strength and the structure of the t- overline{t} -γ vertex. The latter can shed some light on possible new physics that can reveal itself only once sufficiently precise theoretical predictions are available.

An experimental study on the angular dependence of coherent to Compton scattering differential cross-section ratios of calcium

The coherent to Compton scattering cross-section ratio of calcium was measured experimentally for several polar scattering angles (90°, 100°, 110°, 120°, and 130°) and azimuthal scattering angles (30°, 20°, 10°, 0°, -10°, and -20°). A high purity germanium semiconductor detector with a resolution of 199.6 eV at 5.9 keV was used. The theoretical values of the coherent to Compton scattering differential cross-section of calcium were calculated on the basis of nonrelativistic form factors, relativistic form factors, and S-matrix theories. It was observed that the experimental results were most compatible with the nonrelativistic form factor theory.

Measurements of the associated production of a Z boson and b jets in pp collisions at {sqrt{s}} = 8,text {TeV}

Measurements of the associated production of a mathrm{Z} boson with at least one jet originating from a b quark in proton–proton collisions at sqrt{s} = 8,text {TeV} are presented. Differential cross sections are measured with data collected by the CMS experiment corresponding to an integrated luminosity of 19.8,text {fb}^{-1}. mathrm{Z} bosons are reconstructed through their decays to electrons and muons. Cross sections are measured as a function of observables characterizing the kinematics of the mathrm{b} jet and the mathrm{Z} boson. Ratios of differential cross sections for the associated production with at least one mathrm{b} jet to the associated production with any jet are also presented. The production of a mathrm{Z} boson with at least two mathrm{b} jets is investigated, and differential cross sections are measured for the dijet system. Results are compared to theoretical predictions, testing two different flavour schemes for the choice of initial-state partons.