Abstract: The early universe consists of element particles such as quarks and gluons after the big bang. Understanding their interactions is crucial for the physics, especially their interaction strength: do they behave like a gas or like water? A lot of experiments and theoretical calculations have been performed in labs, using different particles to study the properties of the early universe. Luckily, scientists can create this state of matter on earth by proton-proton collisions (or nucleus-nucleus collisions). As this matter produced in the particle collisions last only a very short of time ~ fm/c where c is the speed of light. How to probe this medium becomes difficult? This work suggests that people can study the momentum correlations between particles moving in the opposite direction in the hot medium. If the early universe is a STRONGLY coupled medium, then the medium will change both particles’ momentum. After they move out of the hot medium, their momentum angular is NOT pi anymore. In summary, the hot medium random interactions will change the momentum angular between two particles even their initial momentum is in the opposite direction. This work employs the Langevin equation to simulate their evolutions in the hot medium, and get good results.
For each momentum three well distinguished peaks can be observed. As for all used momenta the electrons travel with almost the speed of light their position in the spectrum remains unchanged—see peaks centered around 0 ns value in figure. The speed of pions and muons is strongly momentum dependent. It is also well seen that positions of their peaks are shifted. Relative distance to the electron peak can be verified in calculations us- ing particlemomentum, its mass and the trajectory length. This allows for assigning of the peak either to pions or muons as well as, from integrated peak intensities, determination of relative contribution of specific particle to the total beam intensity-see Table 1 for results. As the peaks are not only well separated but the space in- between is free of background events, the gamma-ray contamination of the beam is relatively low.
In general, our results are in line with earlier studies of two-component gases of fermions in 1D with an at- tractive contact interaction between the components. In particular, we have illustrated the excellent agreement of our results for the ground-state energy with the exact results from the Bethe ansatz. Moreover, we have found very good agreement for the contact parameter calcu- lated differently in a previous study . Even more, our first comparatively crude estimates for the speed of sound are in accordance with the well-known exact results of this quantity [36–38]. Also in accordance with previ- ous studies [32, 38], we find that, in the weakly-coupled regime with γ . 1, the calculated correlation functions, and therefore also the momentum distributions, are still well approximated by the ones of the non-interacting system. The dynamics in this regime still appears to be dominated by the presence of the Fermi points. In the strongly-coupled regime with γ & 1, we then find that the single-particlemomentum distributions start to flatten out and the pair-momentum distribution devel- ops a pronounced maximum at vanishing pair momen- tum relative to the corresponding distribution of the non- interacting system. Our estimates for the sound veloc- ity reveal that the system undergoes a crossover from the weakly-coupled regime, where the sound velocity re- mains close to the Fermi velocity, to a strongly-coupled regime for γ & 2, where the sound velocity drops dras- tically. In detailed analytic studies of the many-body phase diagram [32, 36–38], this behavior was traced back to the fact that the dynamics of the system is governed by Cooper-type pairing in the weak-coupling limit and by the formation of tight bosonic molecules in the strong- coupling limit.
A nesting architecture with XGBoost classifiers for µ identification is proposed as shown in figure 1. We use two classifiers with all the reconstructed information of EMC and MUC as inputs, respectively. The outputs of the two classifiers together with χ 2 dE/dX and χ 2 TOF are submitted to another classifier for combination. Since PID of hadrons only uses dE/dx and TOF information and PID for electrons used dE/dx, TOF and EMC, user can easily choose which subdetectors to use with the architecture shown in figure 1. In this proceeding, the classifier in trained on a full simulation of µ and π sample uniformly distributed with momentum from 0.1 to 1.4 GeV, cosθ (polar angle) from -0.8 to 0.8. Figure 2 (a) shows the result of ROC curve and figure 2 (b) shows the AUC values varying with particlemomentum (one of the input variables of the classifier). The comparisons indicate the new approach with ML has a better performance than the default muon identification used in BESIII. The performance drops around 0.4 GeV because there is a cut-off of the MUC for those low momentum particles cannot reach the muon counter.
point in the analysis of the tracks is determination of the particle mass that is performed by measuring the particlemomentum p (via measuring a curvature of the trajectory in a known magnetic ﬁeld) and the particle kinetic energy T (via measuring range of the particle in propane). Because of ﬂuctuations in the energy losses in substance measurement of T is the most delicate part of the whole procedure of reconstruction of the mass. Nevertheless V.A. Nikitin successfully demonstrated that it works quite well in the case of known tracks of electrons and muons.
It is important to perform the same femtoscopic studies as for the heavy ion collisions with the system created in very high energy pp collisions at LHC energies. Event multiplicities reached in 7 TeV pp collisions at the LHC are comparable with those measured in peripheral A+A collisions at RHIC, making the study of the particlemomentum and the particle transverse mass dependencies of the correlation radii an important test of the collectivity in pp collisions.
An elementary particle is defined, or should be defined, as one which is not composite. So, all we want to know about an elementary particle is its static properties, mass, charge, spin, etc. When, almost exactly 100 years ago, Rutherford discovered the nucleus, we had just two elementary particles, the electron, and the proton, and there was no question of their constituents. While the electron has remained elementary, we know today that nucleons, proton and neutron, are not. The nucleons are composite of three light, spin 1/2 (m<10 MeV each, charge +2/3 and -1/3) up and down quarks, which are bound by massless spin 1 gluons. Mesons are simpler, being composite of a quark and an antiquark, with the quarks being up, down, and strange.
Particle levitation. Dry silica microspheres of 5 µm in diameter (Thermo Scientific) are preloaded onto a circu- lar glass coverslip (Harvard Apparatus, 150 µm in thick- ness) that is used as the vacuum chamber window for the trapping beam through the MO. A piezo electric trans- ducer (APC International) affixed to the chamber is op- erated at 140 kHz to detach microspheres from the lower glass window to load particles into the optical trap. Sin- gle silica spheres are trapped with a linearly polarised light field at an optical power of 81.6 mW (measured at the back aperture of the MO). Once a single sphere is trapped at atmospheric pressure, the chamber pressure is gradually reduced to ∼ 10 kPa.
correlation function from jet fragmentation is studied, and a new method for constraining its contributions to the measured correlations is described. The measured source sizes are substantially larger in more central collisions and are observed to decrease with increasing pair k T . A correlation with the local single-particle multiplicity dN ch /dy is demonstrated.
Today, CERN’s mission is to use their particle accelerator technologies for research in fundamental physics while uniting people from around the globe . Figure 1 shows the CERN Globe of innovation, a publicly accessible science outreach installation. CERN is at the forefront of scientific discovery and accelerator technology. CERN hosts and operates the Large Hadron Collider (LHC), the world’s largest particle accelerator. The 17-mile-long tunnel sits 50-100 meters below the ground and spans two countries: France and Switzerland. It is also the coldest machine on the planet. The large magnets used to accelerate and steer particles along the ring are cooled to temperatures of nearly 2 K, or -456˚F, which enables them to superconduct electricity to reach the needed magnetic field strength. Ironically, the behemoth machine is also emptier than the vacuum of space. Inside the accelerator is an ultra-high vacuum of 10 -13 atmospheres, so the speeding particles don’t collide with any gas molecules. The LHC accelerates primarily two types of beams: proton-proton (p-p) and lead-lead (Pb-Pb), but also proton-lead (p-Pb) beams. During the latest run, Run II which lasted from 2015-2018, p-p collisions were conducted at 13 TeV center-of-mass energy and 5.5 TeV for Pb-Pb collisions.
A two-dimensional transport modeling applicable to a whole tokamak plasma is proposed. The model is de- rived from the multi-fluid equations and Maxwell’s equations and the moment approach of neoclassical transport is employed as fluid closures. The multi-fluid equations consist of the equations for particle density, momen- tum, energy and total heat flux transport for each plasma species. The expressions of the parallel viscosity and heat viscosity are extended in order to be applicable to both inside and outside of the last closed flux surface. It is confirmed that our neoclassical transport model is consistent with the ordinary flux-surface-averaged one- dimensional neoclassical transport model. Our transport equations are coupled with the electromagnetic equa- tions in order to describe the time evolution of tokamak plasmas. The procedure for coupling a transport solver based on our transport model with an equilibrium solver is also briefly described.
energies, the kinetic energy of the center of mass is zero before, and hence after, the collision. Either way, as the exciting particle leaves the range of the interaction force, the center of mass velocity is constant, so this point can serve as the origin of an inertial reference frame. All particles, composing the system, move in the same inertial frame, hence any transformations of radius vector and time coordinate or energy and momentum of given particle between different inertial systems are not necessary. Both the nonrelativistic and modified relativistic (introduced in ) internal Hamiltonians are invariant with respect to translations. The energy of a stationary state is defined precisely, hence the energy and momentum conservation law (2) is senseless in a fixed reference frame defined for a quantum system by its internal Hamiltonian. Moreover, at a precisely defined energy the time coordinate is completely uncertain, therefore it is not necessary as argument of wave function. At the same time in formalisms, operating with one particle coordinates, all inertial systems have to be equivalent and invariance of formalism with respect to Lorentz transformations is necessary. The space-time interval, defined by scalar product of four-dimensional vectors and invariant with respect to transformations between different inertial frames, requires every particle to have different spatial and time variables. The problems of wave functions presented this way are well known (lattice QCD; for a review, see ). In our formalism we don’t have to worry about interval and mass invariance in different inertial reference systems. Instead, we just modify the internal Hamiltonian of a quantum system by introducing the relativistic kinetic energy operator instead of the nonrelativistic one for every internal spatial coordinate.
at x, t where these four states have been assigned to the particles to keep the track of correlation in the trajecto- ries as they move between lattice sites such that the state- 1 and state-3 correspond to the particle moving to the right and state-2 and state-4 correspond to the left mov-
DOI: 10.4236/jmp.2018.99110 1771 Journal of Modern Physics and/or quadruples as we have seen in this paper. The electrons move no longer on approximately circular orbits, but a cloud of highly excited electrons per- forms a breathing motion caused by diffraction of an electron wave from a po- tential ridge. The breathing is an entirely novel and unexpected electron motion in an atom. In the spectral range near a threshold of multiple escape a resonance would be located due to the long-range Coulomb interaction in an infinity of one-electron continua. The Fano resonance theory  does not apply to that crucial situation. Actually the embedding into a huge number of continua pro- duces the new kind of motion as described here. The main result of the present study has been that quite generally the particle wave diffraction from a potential ridge induces a fictitious force between the constituents of the system under consideration. Moreover, that force may be attractive or repulsive depending on the mode of motion. A few-electron atom is perhaps one of the simplest exam- ples for that situation. We believe that potential surfaces of big molecules show multidimensional ridge structures leading to similar surprising effects.
In relativistic quantum mechanics, elementary particles are described by irreducible unitary representations of the Poin- caré group. The same applies to the center-of-mass kinematics of a multi-particle system that is not subject to external forces. As shown in a previous article, for spin-1/2 particles, irreducibility leads to a correlation between the particles that has the structure of the electromagnetic interaction, as described by the perturbation algorithm of quantum electro- dynamics. The present article examines the consequences of irreducibility for a multi-particle system of spinless parti- cles. In this case, irreducibility causes a gravitational force, which in the classical limit is described by the field equa- tions of conformal gravity. The strength of this force has the same order of magnitude as the strength of the empirical gravitational force.
There is a restriction on the possible states because the electrons we are dealing with are still fermions and are subject to the Pauli exclusion principle. The angular momentum and spin configurations must be antisymmetric under particle exchange, leading to spin and spatial functions having opposite par- ity. With L even symmetric, L odd antisymmetric, S even antisymmetric, and S odd
Abstract. Twisted or vortex particles are a new powerful tool to study atomic and molecular processes as well as phenomena that occur at the level of nano-objects. The main feature of such particles is that they carry a non-zero projection of orbital angular momentum along the beam propagation direction. The process of twisted electron scattering from diatomic molecule targets has been studied in this paper for the first time. The Yukawa potential is selected as a model potential. Numerical calculations are carried out for the case of scattering from a hydrogen molecule H 2 .
with a 0.7 Tm field integral, and other forward detectors for triggering and centrality selection. The ALICE central barrel subdetectors have specific unique capabilities for measuring the production of strange and light-flavour hadrons over a wide range of transverse momentum, from pp and p–Pb interactions up to the highest multiplicity environment of the central Pb–Pb collisions. Tracking and vertexing are performed using the Inner Tracking System (ITS), consisting of six layers of silicon detectors, and the Time Projection Chamber (TPC). The two innermost layers of the ITS and the VZERO detector (scintillation hodoscopes placed on either side of the interaction region) are used for triggering. The VZERO also provides the centrality (multiplicity) class definition in Pb–Pb (pp, p–Pb) collisions, while the ITS and the TPC provide particle identification in the low and intermediate p T region, respectively. The Time Of Flight detector (TOF) and the ring imaging Cherenkov detector
Abstract. A Monte Carlo simulation of real detector eﬀects with as many details as pos- sible has been carried out instead of a simpliﬁed Geant point smearing approach during the study of the detector performance. Some results of realistic simulation of the MPD TPC (Time Projection Chamber) including digitization in central Au+Au collisions have been obtained. Particle identiﬁcation (PID) has been tuned to account for modiﬁcations in the track reconstruction. Some results on hadron identiﬁcation in the TPC and TOF (Time Of Flight) detectors with realistically simulated response have been also obtained.
The same procedure cannot be applied to the decom- position of the toroidal momentum ﬂux. Here the situation is made more involved by the fact that in the local limit, due to symmetry properties satisﬁed by the gyrokinetic equation [4, 22–25], the radial ﬂux of toroidal momentum is zero unless the symmetry is broken by the presence of additional terms in the equation. The identiﬁcation of sym- metry breaking mechanisms provides a physical way to de- compose the radial ﬂux of toroidal momentum. Three main mechanisms can be identiﬁed which break the symmetry and deliver ﬁnite toroidal momentum ﬂux. The ﬁrst is con- nected with the presence of an equilibrium toroidal ﬂow and/or its gradient. The gradient produces the diagonal term, whereas the ﬂow itself is responsible for the turbulent convective term (in addition to and not to be confused with the regular convection which is produced by the presence of a particle ﬂux). As already mentioned, in addition to di- agonal and convective terms, the toroidal momentum ﬂux has residual components of the Reynolds stress. These can be produced by two types of mechanisms. The most obvi- ous one is associated with an up-down asymmetry of the magnetic equilibrium conﬁguration. The other is related to the presence of any eﬀect which leads to the development of ﬁnite average parallel and radial wave numbers, like for instance an equilibrium E × B sheared ﬂow or several other mechanisms which can be identiﬁed when higher orders in the normalized ion Larmor radius parameter ρ ∗ are con- sidered. In conclusion, a physical decomposition of the momentum ﬂux can be obtained in this form [4, 5, 25]