Few-body Studies at Nuclotron-JINR

Recent results on the deuteron analyzing powers in dp- elastic scattering obtained at Nuclotron (JINR, Dubna) are compared with the calculations performed within relativistic multiple scattering model. The data demonstrate strong deviation form the predictions at large angles in the cms. The preliminary data on the energy dependence of the cross section in the dp → ppn reaction at 150–250 MeV/nucleon for different configurations and dp elastic scattering up to 1 GeV obtained at internal target station at Nuclotron are reported. The prospects of the further few-body studies at JINR are discussed.     

Investigation of the angular dependence of the analyzing powers in the deuteron-proton elastic scattering at the nuclotron

New polarimeter based on the asymmetry measurement in dp-elastic scattering has been constructed at internal target at Nuclotron (JINR). The result on the deuteron analyzing powers A _y , A _yy and A _xx in the deuteron-proton (dp) elastic scattering at the energies of 880 and 2000 MeV are presented. They are compared with different theoretical approaches.     

Deuteron beam polarimetry at the nuclotron

The scheme of the deuteron beam polarization measurements at Nuclotron are presented. A deuteron beam polarimeter based on the spin-asymmetry measurements in the dp-elastic scattering at large angles in center-of-mass system has been constructed at the internal target station at the Nuclotron of JINR. This polarimeter is planned to use for the measurements of the vector and tensor components of deuteron beam polarizations at the energies 270–2000 MeV simultaneously. Details on the low energy polarimeters are also discussed.     

GEANT4 simulation of dp non-mesonic breakup reaction at 300 and 500 MeV

GEANT4 simulations of the reaction dp → ppn, i.e. the dp non-mesonic breakup reaction, at 300 and 500 MeV of deuteron energy for different detector configurations are presented. Two threads made from polyethylene and carbon with the thickness of 10 μm are used as targets. The goal of the simulations is to find a method by means of which the signal from the dp non-mesonic breakup can be separated from the background that mainly comes from the carbon content of the CH₂ target. The obtained results will be used in the experimental spin program that will be realized in Nuclotron in Dubna. The aim of this experimental investigation is to contribute to the elucidation of the structure of the spin dependent parts of the nucleon-nucleon and three-nucleon forces acting in the dp non-mesonic breakup. The deuteron energies will be ranging from 300 up to 500 MeV.     

Detection equipment for investigating dp elastic scattering at internal target of nuclotron in the framework of DSS project

A complex of detection equipment based on scintillation detectors for investigating dp elastic scattering at the internal target of the Nuclotron developed in the framework of the Deuteron Spin Structure (DSS) project is presented. The results of optimizing scintillation detectors and the results of test measurements of a deuteron beam of the Nuclotron are given.     

The cross-section in <Emphasis Type="Italic">dp</Emphasis>-elastic scattering at the energies of 500, 700 and 880 MeV obtained at the internal target station of Nuclotron

The results on the cross-section of dp-elastic scattering reaction obtained at 500, 700 and 880 MeV at the internal target of Nuclotron are presented. The measurements have been performed using CH₂ and C targets and kinematic coincidence of signals from scintillation counters. The cross-section data are compared with theoretical predictions and results of previous experiments.     

Thermal expansion of niobium diselenide in the basal plane at low temperatures

The thermal expansion of a high-quality 2H-NbSe₂ single crystal is precisely measured in the basal plane and the temperature range 5.7–50 K. An anomaly of the thermal expansion in the basal plane is detected, and it is found to be caused by a superconducting transition. The change in thermal expansion coefficient α _ab is used to calculate the pressure derivative of the critical temperature (dT _c /dp _ab ) = (19.0 ± 2.0) × 10^?9 K/Pa, and this derivative agrees well with the reported data. An additional anomaly, which indicates a phase transition, is also detected in the pretransition range. The nature of the detected phase transition is discussed.     

Angular dependence of proton inclusive spectra from dp → pX reaction at 3.34 GeV/c

Inclusive differential cross sections for the dp → pX reaction at 3.34 GeV/c are presented for different proton production angles in the deuteron frame. At large angles some irregularities have been observed in the spectra. The obtained angular dependence of the inclusive differential spectra for the backward hemisphere allows a detailed comparison with models describing dp interactions. This comparison shows the importance to consider the contributions from rescattering processes at production angles around 90°. Conclusion is made about the necessity to involve additional mechanisms into existing models in order to describe the angular dependence of the inclusive proton cross sections.     

Elastic backwardpd-scattering in Δ-resonance region

Contribution ofΔ-resonance mechanism to elastic backwardpd-scattering overT ₀ =0.5–0.8 GeV range of incident energy is analyzed. As distinct from [1–3], the parameters ofNN?NΔ amplitudes in the phenomenology of one-mesonπ- andρ-exchange are determined frompp→pnπ ⁺ reaction immediately in the kinematic region where the processpd→dp occurs. It has been found as a result that in the vicinity of the region whereΔ-isobar is present on-mass-shell, the coherent sum of the amplitudes ofΔ-resonance mechanism, relativistic one-nucleon exchange and single scattering predicts thepd→dp cross-section to be twice smaller than the experimental one and does not describe the tensor polarization oft ₂₀ deuteron. Possible causes of this discrepancy as well as the relation between the mechanisms ofpd→dp process and the data on reactions of quasi-elastic knock-out of fast deuterons by protons (p,pd) from light nuclei, are discussed.     

Effect of high pressure on the superconducting transition temperature of Pd-H

Under hydrostatic pressure a negativedT _c /dp comparable to that of non-transition superconductors has been found for Pd-H. A simple model is discussed, which is able to explain the isotope-effect in Pd-H(D), and which is in agreement with the observed pressure effect.     

Dark matter production at the LHC from black hole remnants

We study dark matter production at CERN LHC from black hole remnants (BHR). We find that the typical mass of these BHR at the LHC is ∼5–10 TeV which is heavier than other dark matter candidates, such as axion, axino, neutralino, etc. We propose the detection of this dark matter via single jet production in the process pp → jet + BHR (dark matter) at CERN LHC. We find that for zero impact parameter partonic collisions, the monojet cross section is not negligible in comparison to the standard model background and is much higher than the other dark matter scenarios studied so far. We also find that dσ/dp _T of jet production in this process increases as p _T increases, whereas in all other dark matter scenarios the dσ/dp _T decreases at CERN LHC. This may provide a useful signature for dark matter detection at the LHC. However, we find that when the impact parameter dependent effect of inelasticity is included, the monojet cross section from the above process becomes much smaller than the standard model background and may not be detectable at the LHC.     

Superconductivity in α- and ω-Zirconium under high pressure

The pressure dependence of the superconducting transition temperatureT _c (p) of α-Zr has been investigated in both solid and liquid pressure transmitting media. Up to about 45 kbardT _c /dp was measured to be + 3.5 × 10^?6 K/bar. Cold working at 4.2 K produced a strong irreversible effect onT _c . The superconductivity of the high pressure phase, ω-Zr, has been studied in its region of stability, i.e. above 60 kbar. For ω-Zr,dT _c /dp=+7.7 × 10^?6K/bar, andT _c (0)=0.72 K (by extrapolation).     

Destruction of pressure-induced superconductivity by long-range antiferromagnetic order in Tm2Fe3Si5

Reentrant superconductivity has been detected in a well characterized sample of Tm₂Fe₃Si₅ by ac susceptibility measurements under applied pressure. The superconducting transition temperature displays a pronounced, non-linear behavior under pressure, starting at low pressures with an increase which is among the largest known for any compound (dT_c1/dp = 0.47 K/kbar). The magnetic transition temperature is relatively pressure independent.     

Effect of hydrostatic pressure on the HgTe optical phonon

We have measured the reflectivity from 20–240cm^?1 of HgTe samples at 80 K and below as a function of hydrostatic pressure to 8 kbars. The transverse optical phonon frequency was determined from a Kramers-Kronig analysis of the data. For three samples of different doping levels we find dω_TO/dp = 0.34 cm^?1 kbar^?1. The Gruneissen's parameter, γ = 1.2, is typical of values for zincblende crystals indicating that the phonon is not influenced by the narrow gap and inverted band structure. The defect oscillator at 107 cm^?1 is observed to be independent of pressure. This appears inconsistent with its identification as a phonon difference mode.     

Quantum particle trajectories and geometric phase

Particle trajectories are defined as integrable dx _μ dp ^μ=0 paths in projective space. Quantum states evolving on such trajectories, open or closed, do not delocalize in (x, p) projection, the phase associated with the trajectories related to the geometric (Berry) phase and the classical mechanics action. Properties at high energies of the states evolving on particle trajectories are discussed.     

Study of Tensor Correlations in 4He via the 4He(p, dp)d and 4He(p, dp)pn Reactions

Tensor correlations in ⁴He were studied via the (p, dp) reaction at the incident energy of 392 MeV with a focus on spin configurations of correlated pn pairs in ⁴He at high relative momenta ${(P_{\rm rel}^{\rm cor})}$ . The preliminary results show that the correlated pn pair at ${P_{\rm rel}^{\rm cor} = 310 {\rm MeV/c}}$ predominantly has the channel spin S = 1, which is consistent with the characteristics of tensor correlations.     

Measurements of the ratio Rdp of the quasi-elastic nd \rightarrow p(nn) to the elastic np \rightarrow pn charge-exchange process yields at zero proton emission angle over the 0.55-2.0 GeV neutron beam energy region

New experimental results on the ratio R_dp of the quasi-elastic charge-exchange yield at the outgoing proton angle $ \theta_{{p,{\rm Lab}}}^{}$ = 0^° for the nd $ \rightarrow$ p(nn) reaction to the elastic np $ \rightarrow$ pn charge-exchange yield are presented. The measurements were carried out at the Nuclotron of the Veksler and Baldin Laboratory of High Energies of the JINR (Dubna) at the neutron beam kinetic energies of 0.55, 0.8, 1.0, 1.2, 1.4, 1.8 and 2.0GeV. The intense neutron beam with small momentum spread was produced by break-up of deuterons which were accelerated and extracted to the experimental hall. In both reactions mentioned above the outgoing protons with the momenta p _p approximately equal to the neutron beam momentum p _{n, beam} were detected in the directions close to the direction of incident neutrons, i.e. in the vicinity of the scattering angle $ \theta_{{p,{\rm Lab}}}^{}$ = 0^° . Measured in the same data taking runs, the angular distributions of the charge-exchange reaction products were corrected for the well-known instrumental effects and averaged in the vicinity of the incident neutron beam direction. These corrected angular distributions for every of nd $ \rightarrow$ p(nn) and np $ \rightarrow$ pn charge-exchange processes were proportional to the differential cross-sections of the corresponding reactions. The data were accumulated by the Delta-Sigma set-up magnetic spectrometer with two sets of multiwire proportional chambers located upstream and downstream of the momentum analyzing magnet. Inelastic processes were considerably reduced by the additional detectors surrounding the hydrogen and deuterium targets. The time-of-flight system was applied to identify the detected particles. The new R_dp data are compared with the existing ones, which were obtained below 1GeV, and with the calculations which were made using the phenomenological NN amplitude sets.     

Refined MCHF evaluations of field isotope shift and hyperfine structure in the calcium atom

In the calcium atom, the MCHF method has been applied for evaluating the field-shift electronic parts of both 4s ²-4s4p lines, and the hyperfine-structure electronic effective parameters of the 4s4p ³ P ₂ and¹ P ₁ levels. For the hyperfine structures, the far-configuration mixing corrections have been computed with the assumption that the lower state is itself a two-componentsp+dp state in close-configuration mixing.     

Energies of mass-asymmetric Coulomb systems

It is found that particle-mass-symmetric and particle-mass-asymmetric Coulomb systems are adiabatically similar. Expressions are proposed for the mass dependence of upper and lower bounds on the energies of asymmetric systems, and an expression approximating these energies is given. The energies of the families of mesic molecules that are adiabatically similar to the mesic molecules dpμ, tpμ, and tdμ are investigated with the aid of these expressions.