arXiv subjects

S. Trusov

Publications and source records attributed to S. Trusov.

At least 19 recordsLinked to original sources

arXiv2024

The \pi^+\pi^- Coulomb interaction study and its use in the data processing

In this work the Coulomb effects (Coulomb correlations) in $\pi^+\pi^-$ pairs produced in p + Ni collisions at 24 GeV/$c$, are studied using experimental $\pi^+\pi^-$ pair distributions in $Q$, the relative momentum in the pair center of mass system (c.m.s), and its projections $Q_L$ (longitudinal component) and $Q_t$ (transverse component) relative to the pair direction in the laboratory system (l.s.). The $Q$, $Q_L$, and $Q_t$ distributions of the {\sl Coulomb pairs} in the c.m.s. have been simulated assuming they are described by the phase space modified by the known point-like Coulomb correlation function $A_C(Q)$, corrected for small effects due to the nonpoint-like pair production and the strong two-pion interaction. The same distributions of {\sl non-Coulomb pairs} have been simulated according to the phase space, but without $A_C(Q)$. It is shown that the number of {\sl Coulomb pairs} in all $Q_t$ intervals, including the small $Q_t$ (small opening angles $\theta$ in the l.s.) is calculated with the theoretical precision better than 2\%. The comparison of the simulated and experimental numbers of {\sl Coulomb pairs} at small $Q_t$ allows us to check and correct the detection efficiency for the pairs with small $\theta$ (0.06 mrad and smaller). It is shown that {\sl Coulomb pairs} can be used as a new physical tool to check and correct the quality of the simulated events. The special property of the {\sl Coulomb pairs} is the possibility of checking and correcting the detection efficiency, especially for the pairs with small opening angles.

hep-ph↗

arXiv2022

The Uchuu-SDSS galaxy lightcones: a clustering, RSD and BAO study

We present the data release of the Uchuu-SDSS galaxies: a set of 32 high-fidelity galaxy lightcones constructed from the large Uchuu 2.1 trillion particle $N$-body simulation using Planck cosmology. We adopt subhalo abundance matching to populate the Uchuu-box halo catalogues with SDSS galaxy luminosities. These cubic box galaxy catalogues generated at several redshifts are combined to create the set of lightcones with redshift-evolving galaxy properties. The Uchuu-SDSS galaxy lightcones are built to reproduce the footprint and statistical properties of the SDSS main galaxy survey, along with stellar masses and star formation rates. This facilitates direct comparison of the observed SDSS and simulated Uchuu-SDSS data. Our lightcones reproduce a large number of observational results, such as the distribution of galaxy properties, the galaxy clustering, the stellar mass functions, and the halo occupation distributions. Using the simulated and real data we select samples of bright red galaxies at $z_\mathrm{eff}=0.15$ to explore Redshift Space Distortions and Baryon Acoustic Oscillations (BAO) utilizing a full-shape analytical model of the two-point correlation function. We create a set of 5100 galaxy lightcones using GLAM N-body simulations to compute covariance errors. We report a $\sim 30\%$ precision increase on $fσ_8$, due to our better estimate of the covariance matrix. From our BAO-inferred $α_{\parallel}$ and $α_{\perp}$ parameters, we obtain the first SDSS measurements of the Hubble and angular diameter distances $D_\mathrm{H}(z=0.15) / r_d = 27.9^{+3.1}_{-2.7}$, $D_\mathrm{M}(z=0.15) / r_d = 5.1^{+0.4}_{-0.4}$. Overall, we conclude that the Planck LCDM cosmology nicely explains the observed large-scale structure statistics of SDSS. All data sets are made publicly available.

astro-ph.CO↗

arXiv2022

Investigation of $K^+K^-$ pairs in the effective mass region near $2m_K$

The DIRAC experiment at CERN investigated in the reaction $\rm{p}(24~\rm{GeV}/c) + Ni$ the particle pairs $K^+K^-, π^+ π^-$ and $p \bar{p}$ with relative momentum $Q$ in the pair system less than 100 MeV/c. Because of background influence studies, DIRAC explored three subsamples of $K^+K^-$ pairs, obtained by subtracting -- using time-of-flight (TOF) technique -- background from initial $Q$ distributions with $K^+K^-$ sample fractions more than 70\%, 50\% and 30\%. The corresponding pair distributions in $Q$ and in its longitudinal projection $Q_L$ were analyzed first in a Coulomb model, which takes into account only Coulomb final state interaction (FSI) and assuming point-like pair production. This Coulomb model analysis leads to a $K^+K^-$ yield increase of about four at $Q_L=0.5$ MeV/c compared to 100 MeV/c. In order to study contributions from strong interaction, a second more sophisticated model was applied, considering besides Coulomb FSI also strong FSI via the resonances $f_0(980)$ and $a_0(980)$ and a variable distance $r^*$ between the produced $K$ mesons. This analysis was based on three different parameter sets for the pair production. For the 70\% subsample and with best parameters, $3680\pm 370$ $K^+K^-$ pairs was found to be compared to $3900\pm 410$ $K^+K^-$ extracted by means of the Coulomb model. Knowing the efficiency of the TOF cut for background suppression, the total number of detected $K^+K^-$ pairs was evaluated to be around $40000\pm 10\%$, which agrees with the result from the 30\% subsample. The $K^+K^-$ pair number in the 50\% subsample differs from the two other values by about three standard deviations, confirming -- as discussed in the paper -- that experimental data in this subsample is less reliable.

hep-ex↗

arXiv2018

Resonance-like coherent production of a pion pair in the reaction $pd \rightarrow pdππ$ in the GeV region

The reaction $p + d \rightarrow p + d + X$ was studied at 0.8-2.0 GeV proton beam energies with the ANKE magnetic spectrometer at the COSY synchrotron storage ring. The proton-deuteron pairs emerging with high momenta, 0.6-1.8 GeV/$c$, were detected at small angles with respect to the proton beam. Distribution over the reaction missing mass $M_x$ reveals a local enhancement near the threshold of the pion pair production specific for the so-called ABC effect. The enhancement has a structure of a narrow bump placed above a smooth continuum. The invariant mass of the $dππ$ system in this enhancement region exhibits a resonance-like peak at $M_{dππ} \approx 2.36$ GeV/$c^2$ with the width $Γ\approx 0.10$ GeV/$c^2$. A possible interpretation of these features is discussed.

nucl-ex↗

arXiv2018

First measurement of a long-lived $π^+ π^-$ atom lifetime

The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogen-like $π^+π^-$ atoms, produced by protons hitting a beryllium target. A part of these atoms crossed the gap of 96~mm and got broken up in the 2.1~\textmu{}m thick platinum foil. Analysing the observed number of atomic pairs, $n_A^L= \left.436^{+157}_{-61}\right|_\mathrm{tot}$, the lifetime of the 2$p$ state is found to be ${τ_{2p}=(\left.0.45^{+1.08}_{-0.30}\right|_\mathrm{tot}) \cdot10^{-11}}$s, not contradicting the corresponding QED $2p$ state lifetime ${τ_{2p}^\mathrm{QED}=1.17 \cdot 10^{-11}}$s. This lifetime value is three orders of magnitude larger than our previously measured value of the $π^+π^-$ atom ground state lifetime $τ=(\left.3.15^{+0.28}_{-0.26}\right|_\mathrm{tot})\cdot 10^{-15}$s. Further studies of long-lived $π^+π^-$ atoms will allow to measure energy differences between $p$ and $s$ atomic states and so to determine $ππ$ scattering lengths with the aim to check QCD predictions.

hep-ex↗

arXiv2018

Measurement of the analyzing powers in pd elastic and pn quasi-elastic scattering at small angles

The analyzing powers in proton-deuteron elastic and proton-neutron quasi-elastic scattering have been measured at small angles using a polarized proton beam at the COSY storage ring incident on an unpolarized deuterium target. The data were taken at 796MeV and five higher energies from 1600MeV to 2400MeV. The analyzing power in pd elastic scattering was studied by detecting the low energy recoil deuteron in telescopes placed symmetrically in the COSY plane to the left and right of the beam whereas for pn quasi-elastic scattering a low energy proton was registered in one of the telescopes in coincidence with a fast scattered proton measured in the ANKE magnetic spectrometer. Though the experiment explores new domains, the results are consistent with the limited published information.

nucl-ex↗

arXiv2017

Measurement of the $πK$ atom lifetime and the $πK$ scattering length

After having announced the statistically significant observation (5.6~$σ$) of the new exotic $πK$ atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding atom lifetime, based on the full $πK$ data sample: $τ= (5.5^{+5.0}_{-2.8}) \cdot 10^{-15}s$. By means of a precise relation ($<1\%$) between atom lifetime and scattering length, the following value for the S-wave isospin-odd $πK$ scattering length $a_0^{-}~=~\frac{1}{3}(a_{1/2}-a_{3/2})$ has been derived: $\left|a_0^-\right| = (0.072^{+0.031}_{-0.020}) M_π^{-1}$.

hep-ex↗

arXiv2016

Measurement of spin observables in the quasi-free np-> {pp}_s pi- reaction at 353 MeV

The transverse spin correlations A_{x,x} and A_{y,y} have been measured in the pol{d} pol{p} -> p_spec {pp}_s pi- reaction at COSY-ANKE at 353 MeV per nucleon. Here {pp}_s denotes a proton-proton pair with low excitation energy, which is dominantly in the 1S0 state. By measuring three protons in the final state it was possible to extract events where there was a spectator proton p_spec so that the reaction could be interpreted in terms of quasi-free pol{n} pol{p} -> {pp}_s pi-. The proton analyzing power in this reaction was also deduced from this data set by averaging over the polarization of the deuteron beam. The values of A_y^p were shown to be consistent with a refined analysis of our earlier results obtained with a polarized proton incident on a deuterium target. Taking these data in combination with our earlier measurements of the differential cross sections and analyzing powers in the pol{p} p -> {pp}_s pi^0 reaction, a more robust partial wave decomposition was achieved. Three different acceptable solutions were found and the only way of resolving this ambiguity without further theoretical input would be through a measurement of the mixed spin-correlation parameter A_{x,z}.

nucl-ex↗

arXiv2016

Coherent pion production in proton-deuteron collisions

Values of the proton analysing power in the $pd\to{}^{3}\textrm{He}\,π^0/^{3}\textrm{H}\,π^+$ reactions at 350-360~MeV per nucleon were obtained by using a polarised proton beam incident on a deuterium cluster-jet target and with a polarised deuteron beam incident on a target cell filled with polarised hydrogen. These results have a much larger angular coverage than existing data. First measurements are also presented of the deuteron vector analysing power and the deuteron-proton spin correlations. Data were also obtained on the deuteron-proton spin correlation and proton analysing power at small angles at 600~MeV per nucleon, though the angular coverage at this energy was much more restricted even when using a deuteron beam. By combining the extrapolated values of the spin correlations to the forward or backward directions with published measurements of the deuteron tensor analysing powers, the relative phases between the two non-vanishing amplitudes were evaluated.

nucl-ex↗

arXiv2015

Kaon pair production in proton-nucleus collisions at 2.83 GeV kinetic energy

The production of non-phi K+K- pairs by protons of 2.83 GeV kinetic energy on C, Cu, Ag, and Au targets has been investigated using the COSY-ANKE magnetic spectrometer. The K- momentum dependence of the differential cross section has been measured at small angles over the 0.2--0.9 GeV/c range. The comparison of the data with detailed model calculations indicates an attractive K- -nucleus potential of about -60 MeV at normal nuclear matter density at a mean momentum of 0.5 GeV/c. However, this approach has difficulty in reproducing the smallness of the observed cross sections at low K- momenta.

nucl-ex↗

arXiv2015

Null-test signal for T-invariance violation in $pd$ scattering

The integrated proton-deuteron cross section $\widetildeσ$ for the case of the incident proton vector polarization $p_y^p$ and tensor polarization $P_{xz}$ of the deuteron target provides a null test signal for time-reversal invariance violating but P-parity conserving (TVPC) effects. We study the null-test observable $\widetildeσ$ within the Glauber theory of the double-polarized $pd$ scattering. Full spin dependence of the ordinary strong $pN$ scattering amplitudes and different types of the hypothetical TVPC pN-amplitudes are taken into account. We show that the contribution from the exchange of the lowest-mass meson allowed in the TVPC interaction, i.e. the $ρ$-meson, to the null-test observable $\widetildeσ$ is zero. The axial $h_1$ meson exchange makes a non-zero contribution. We find that inclusion of the Coulomb interaction does not lead to divergence of the cross section $\widetildeσ$ and calculate its energy dependence at the proton beam energy 100-1000 MeV.

nucl-th↗

arXiv2015

Toward polarized antiprotons: Machine development for spin-filtering experiments

The paper describes the commissioning of the experimental equipment and the machine studies required for the first spin-filtering experiment with protons at a beam kinetic energy of $49.3\,$MeV in COSY. The implementation of a low-$β$ insertion made it possible to achieve beam lifetimes of $τ_{\rm{b}}=8000\,$s in the presence of a dense polarized hydrogen storage-cell target of areal density $d_{\rm t}=(5.5\pm 0.2)\times 10^{13}\,\mathrm{atoms/cm^{2}}$. The developed techniques can be directly applied to antiproton machines and allow for the determination of the spin-dependent $\bar{p}p$ cross sections via spin filtering.

physics.acc-ph↗

arXiv2015

Analysing powers and spin correlations in deuteron-proton charge exchange at 726 MeV

The charge exchange of vector polarised deuterons on a polarised hydrogen target has been studied in a high statistics experiment at the COSY-ANKE facility at a deuteron beam energy of Td = 726 MeV. By selecting two fast protons at low relative energy E_{pp}, the measured analysing powers and spin correlations are sensitive to interference terms between specific neutron-proton charge-exchange amplitudes at a neutron kinetic energy of Tn ~ 1/2 Td =363 MeV. An impulse approximation calculation, which takes into account corrections due to the angular distribution in the diproton, describes reasonably the dependence of the data on both E_{pp} and the momentum transfer. This lends broad support to the current neutron-proton partial-wave solution that was used in the estimation.

nucl-ex↗

arXiv2014

Measurement of the analysing power in proton-proton elastic scattering at small angles

The proton analysing power in $\vec{p}p$ elastic scattering has been measured at small angles at COSY-ANKE at 796 MeV and five other beam energies between 1.6 and 2.4 GeV using a polarised proton beam. The asymmetries obtained by detecting the fast proton in the ANKE forward detector or the slow recoil proton in a silicon tracking telescope are completely consistent. Although the analysing power results agree well with the many published data at 796 MeV, and also with the most recent partial wave solution at this energy, the ANKE data at the higher energies lie well above the predictions of this solution at small angles. An updated phase shift analysis that uses the ANKE results together with the World data leads to a much better description of these new measurements.

nucl-ex↗

arXiv2014

Study of the $\vec{p}d \to n\{pp\}_{s}$ charge-exchange reaction using a polarised deuterium target

The vector and tensor analysing powers, $A_y$ and $A_{yy}$, of the $\vec{p}d \to n\{pp\}_{s}$ charge-exchange reaction have been measured at a beam energy of 600 MeV at the COSY-ANKE facility by using an unpolarised proton beam incident on an internal storage cell target filled with polarised deuterium gas. The low energy recoiling protons were measured in a pair of silicon tracking telescopes placed on either side of the target. Putting a cut of 3 MeV on the diproton excitation energy ensured that the two protons were dominantly in the $^{1}S_{0}$ state, here denoted by $\{pp\}_{s}$. The polarisation of the deuterium gas was established through measurements in parallel of proton-deuteron elastic scattering. By analysing events where both protons entered the same telescope, the charge-exchange reaction was measured for momentum transfers $q\geq 160$ MeV/$c$. These data provide a good continuation of the earlier results at $q\leq 140$ MeV/$c$ obtained with a polarised deuteron beam. They are also consistent with impulse approximation predictions with little sign evident for any modifications due to multiple scatterings.

nucl-ex↗

arXiv2014

Absence of spin dependence in the final state interaction of the d(pol) p --> 3He eta reaction

The deuteron tensor analysing power t_{20} of the d(pol) p --> 3He eta reaction has been measured at the COSY-ANKE facility in small steps in excess energy Q up to Q = 11 MeV. Despite the square of the production amplitude varying by over a factor of five through this range, t_{20} shows little or no energy dependence. This is evidence that the final state interaction causing the energy variation is not influenced by the spin configuration in the entrance channel. The weak angular dependence observed for t_{20} provides useful insight into the amplitude structure near threshold.

nucl-ex↗

arXiv2014

First $πK$ atom lifetime and $πK$ scattering length measurements

The results of a search for hydrogen-like atoms consisting of $π^{\mp}K^{\pm}$ mesons are presented. Evidence for $πK$ atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic $πK$ pairs from their breakup in the same target ($178 \pm 49$) and from Coulomb final state interaction ($653 \pm 42$). Using these results the analysis yields a first value for the $πK$ atom lifetime of $τ=(2.5_{-1.8}^{+3.0})$ fs and a first model-independent measurement of the S-wave isospin-odd $πK$ scattering length $\left|a_0^-\right|=\frac{1}{3}\left|a_{1/2}-a_{3/2}\right|= \left(0.11_{-0.04}^{+0.09} \right)M_π^{-1}$ ($a_I$ for isospin $I$).

nucl-ex↗

arXiv2013

First measurements of spin correlations in the np -> d pi^0 reaction

The transverse spin correlations Axx and Ayy in the np-> d pi^0 reaction have been measured for the first time in quasi-free kinematics at the COSY-ANKE facility using a polarised deuteron beam incident on a polarised hydrogen cell target. The results obtained for neutron energies close to 353 MeV and 600 MeV are in good agreement with the partial wave analysis of data on the isospin-related pp-> d pi^+ reaction, though the present results cover also the small-angle region, which was largely absent from these data.

nucl-ex↗