A search for dark matter particle candidates produced in association with a Z boson in proton-proton collisions at the total center-of-mass energy of 13 TeV is presented. The search uses 36.1 inverse ...femtobarn of data collected by the ATLAS experiment at the Large Hadron Collider in 2015 and 2016. Events with large missing transverse momentum and consistent with the decay of a Z boson into oppositely charged electron or muon pairs were selected in the analysis. Background estimates and corresponding systematic uncertainties are shown. Exclusion limits on the dark matter candidate and mediator masses are reported.
We study Landau–Ginzburg orbifolds
with
and
, where
and
is either the maximal group of scalar symmetries of
or the intersection of the maximal diagonal symmetries of
with
. We construct a mirror map ...between the corresponding phase spaces and prove that it is an isomorphism restricted to a certain subspace of the phase space when
is a prime number. When
satisfies the parity condition of Ebeling–Gusein-Zade, this subspace coincides with the full space. We also show that two phase spaces are isomorphic for
.
Differential cross sections for scattering of helium atoms formed at collisions of He
2+
ions with kinetic energies of 1.97, 3.00, and 7.17 keV/a.m.u with Xe atoms in processes with the formation of ...slow xenon ions with charges 2–4 have been measured. The projectiles deflection function is calculated. The probability of all these processes occurring at various values of the impact parameter of colliding particles is determined. The role of the electron shells of the Xe atom 5(
s
,
p
) and 4(
s
,
p
,
d
) for the capture of two electrons is determined depending on the speed of approach of the colliding particles, the impact parameter and the charge of the formed xenon ions.
The single electron capture process from adenine molecules by H
+
,
3
He
+
, N
+
, O
+
, and Ne
+
ions with an energy of 6.3 keV has been studied. It was found that when one electron is captured by ...He
+
and Ne
+
ions, the dissociative capture process is dominant, which is fundamentally different from the processes of capture by singly charged ions of atoms with a lower ionization potential and multiply charged ions, as well as from the process of electron impact ionization. This effect is qualitatively explained within the framework of a quasimolecular model.
In this paper we have studied a mechanism for radiation damage of gas phase molecules of glycine Gly and dipeptide derivatives of glycine, such as diglycine Gly-Gly, cyclo(glycylglycyl) ...cyclo(Gly-Gly) and glycyl-leucine Gly-Leu by the impact of He2+ ions with energy Ep = 4 keV/u. Relative cross sections of different elementary processes occurring in single collisions between dipeptide derivatives of glycine and ions have been measured for the first time. The fragmentation channels of both singly and multiply charged molecular ions have been studied experimentally. It has been shown that in the process of Gly-Gly sublimation, cyclization in the crystalline sample takes place, which results in formation of cyclo(Gly-Gly). Using the DFT method, the geometry of molecules and singly charged ions of glycine dipeptide derivatives has been calculated, as well as energies of different experimentally observed fragmentation channels of these ions.
•The cross sections for the interaction of ions with dipeptides were measured.•The fragmentation of singly and multiply charged dipeptides ions have been studied.•The fragmentation energies of dipeptide ions has been calculated.•Studied the composition of molecular jets formed by sublimation of dipeptides.•Quantum chemical calculations for the geometry of dipeptide ions has been done.
Fast ATLAS Tracking Simulation (Fatras) package was verified on single layer geometry with respect to full simulation with GEANT4. Fatras hadronic interactions and multiple scattering simulation were ...studied in comparison with GEANT4. Disagreement was found in multiple scattering distributions of primary charged particles (μ, π,
e
). A new model for multiple scattering simulation was implemented in Fatras. The model was based on R. Frühwirth’s mixture models. New model was tested on single layer geometry and a good agreement with GEANT4 was achieved. Also a comparison of reconstructed tracks’ parameters was performed for Inner Detector geometry, and Fatras with new multiple scattering model proved to have better agreement with GEANT4. New model of multiple scattering was added as a part of Fatras package in the development release of ATLAS software—ATHENA.
The Fast Simulation Chain for ATLAS Basalaev, A; Marshall, Z
Journal of physics. Conference series,
10/2017, Volume:
898, Issue:
4
Journal Article
Peer reviewed
Open access
In order to generate the huge number of Monte Carlo events that will be required by the ATLAS experiment over the next several runs, a very fast simulation is critical. Fast detector simulation ...alone, however, is insufficient: with very high numbers of simultaneous proton-proton collisions expected in Run 3 and beyond, the digitization (detector response emulation) and event reconstruction time quickly become comparable to the time required for detector simulation. The ATLAS Fast Chain simulation has been developed to solve this problem. Modules are implemented for fast simulation, fast digitization, and fast track reconstruction. The application is sufficiently fast-several orders of magnitude faster than the standard simulation-that the simultaneous proton-proton collisions can be generated during the simulation job, so Pythia8 also runs concurrently with the rest of the algorithms. The Fast Chain has been built to be extremely modular and flexible, so that each sample can be custom-tailored to match the resource and modeling accuracy needs of an analysis. It is ideally suited for analysis templating, systematic uncertainty evaluation, signal parameter space scans, and simulation with alternative detector configurations (e.g. upgrade), among other applications.
The mechanism of radiation damage to 2,5-diketopiperazine (DKP, C
4
H
6
N
2
O
2
) molecules in the gas phase upon interaction with He
2+
ions with an energy
Ep
= 4 keV/u has been investigated. The ...relative cross sections of various elementary processes occurring in single collisions of DKP with ions have been measured for the first time. The channels of fragmentation processes of singly charged ions have been studied experimentally. The DFT method was used to calculate the geometry of molecules and singly charged DKP ions, as well as the energies of the main experimentally observed channels of fragmentation of these ions.
In the framework of this paper, an investigation of the vertical axisymmetric pipe filling with a viscous fluid against the gravity force is implemented. The fluid flow is described by Navier-Stokes ...and continuity equations. On the free surface, the shear stress is equal to zero and the normal stress is equal to the sum of external and capillary pressure. The free surface motion is defined by the kinematic condition. On the solid wall, the velocity is set to zero. At the inlet section, the Poiseuille profile is used. Along the symmetry axis, the symmetry condition is assigned. A numerical solution to the problem is obtained using the control volume method and SIMPLE algorithm. The method of invariants is applied for compliance of the natural boundary conditions on the free surface. The effect of dimensionless criteria on the steady-state shape of the free surface was parametrically studied.
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