Charm Particles Research Articles

Spectra and angle distributions of the atmospheric neutrinos and muons from the charm particle decays

A new calculation of the prompt component of atmospheric leptons — muon neutrinos and muons from the decays of charmed particles is performed for the same hadron cascade model that was used in calculating the characteristics of atmospheric leptons from the decays of π- and K-mesons. Spectral zenith-angular distributions of prompt and (π, K)-leptons are obtained. The cross-energy intervals are found for which the prompt lepton fluxes contribution comparably to the fluxes of (π, K)-muons and neutrinos. The possibility is shown of the prompt neutrinos detecting at energies much lower of the cross-energy.

Spectra and Angle Distributions of Atmospheric Neutrinos and Muons from the Decay of Charm Particles

Spectra and Angle Distributions of Atmospheric Neutrinos and Muons from the Decay of Charm Particles

A high-resolution pixel silicon Vertex Detector for open charm measurements with the NA61/SHINE spectrometer at the CERN SPS

The study of open charm meson production provides an efficient tool for the investigation of the properties of hot and dense matter formed in nucleus–nucleus collisions. The interpretation of the existing di-muon data from the CERN SPS suffers from a lack of knowledge on the mechanism and properties of the open charm particle production. Due to this, the heavy-ion programme of the NA61/SHINE experiment at the CERN SPS has been extended by precise measurements of charm hadrons with short lifetimes. A new Vertex Detector for measurements of the rare processes of open charm production in nucleus–nucleus collisions was designed to meet the challenges of track registration and high resolution in primary and secondary vertex reconstruction. A small-acceptance version of the vertex detector was installed in 2016 and tested with Pb + Pb collisions at 150A,text{ GeV }!/!c. It was also operating during the physics data taking on Xe + La and Pb + Pb collisions at 150A,text{ GeV }!/!c conducted in 2017 and 2018. This paper presents the detector design and construction, data calibration, event reconstruction, and analysis procedure.

Optimizing the zenith angle dependence of cosmic ray muons from Charm particles in the knee region: simulation study

The muonic component of air showers is one of the most abundant component of charged particles arriving at the Earth’s surface, and able to penetrate deeply underground, and is very sensitive to the primary mass and energy of the initial cosmic particle. Atmospheric muons are produced in the propagation of different components of extensive air showers. Therefore, variations in the muon ratio, defined as the number of positive over negative charged muons, must be well understood. In this paper, we study the variation of the muon charge ratio of cosmic muons at different zenith angles, and we study the contribution of charm particles in producing atmospheric muons using Monte Carlo showers initiated by two cosmic primaries, proton and iron, with four energies [10 PeV, 100 PeV, 1 EeV, 10 EeV], in the zenith range of [0° to 60°].

Track and vertex reconstruction using moving emulsion blocks and a silicon pixel tracker for particles induced by 400 GeV/c protons on a thick target

The SHiP-charm experiment is designed to measure the charm production cross section, including cascade production, of 400 GeV/c protons hitting a thick, SHiP-like target. For the detection of production and decay of heavy charmed particles, emulsion films are employed in a multilayered moving target, forming an emulsion cloud chamber. While the emulsion films provide excellent spatial resolution they do not provide timing information, integrate all events, and quickly get saturated. For the charm measurement the emulsion target is thus moving at a constant speed during data-taking. A first optimization run at the CERN SPS has been performed in 2018, with the purpose to develop the required analysis tools and to fine-tune the detector layout. We report on the experiment design, track reconstruction in the pixel tracker and the track matching with the moving emulsion detector.

Multipomeron Model with Collective Effects for High-Energy Hadron Collisions

We propose the generalized multipomeron exchange model for multiparticle production in high-energy proton–proton, proton–nucleus and heavy-ion collisions. For all of these systems, we consider collectivity effects based on the quark–gluon string fusion concept, where new types of particle-emitting sources—strings with higher tension—are produced. We obtained the model parameters using the data on the multiplicity dependence of the mean transverse momentum of charged particles in pp and pp¯ collisions over a wide energy range (from ISR to LHC). We calculated the yields of strange, multi-strange and charm particles as a function of multiplicity for pp, p-Pb and Pb-Pb collisions at the LHC energy and compared the results with the experimental data.

A Vector Finder Toolkit for Track Reconstruction in MPD ITS

As a part of the future upgrade program of the Multi-Purpose Detector (MPD) experiment at the Nuclotron-Based Ion Collider Facility (NICA) complex, an Inner Tracking System (ITS) made of Monolitic Active Pixel Sensors (MAPSs) is proposed between the beam pipe and the Time Projection Chamber (TPC). It is expected that the new detector will enhance the experimental potential for the reconstruction of short-lived particles—in particular, those containing the open charm particle. To study the detector performance and select its best configuration, a track reconstruction approach based on a constrained combinatorial search was developed and implemented as a software toolkit called Vector Finder. This paper describes the proposed approach and demonstrates its characteristics for primary and secondary track finding in ITS, ITS-to-TPC track matching and hyperon reconstruction within the MPD software framework. The results were obtained on a set of simulated central gold–gold collision events at sNN=9 GeV with an average multiplicity of ∼1000 charged particles in the detector acceptance produced with the Ultra-Relativistic Quantum Molecular Dynamics (UrQMD) generator.

First observation of a tau neutrino charged current interaction with charm production in the OPERA experiment

An event topology with two secondary vertices compatible with the decay of short-lived particles was found in the analysis of neutrino interactions in the OPERA target. The observed topology is compatible with tau neutrino charged current (CC) interactions with charm production and neutrino neutral current (NC) interactions with coverline{c} pair production. However, other processes can mimic this topology. A dedicated analysis was implemented to identify the underlying process. A Monte Carlo simulation was developed and complementary procedures were introduced in the kinematic reconstruction. A multivariate analysis technique was used to achieve an optimal separation of signal from background. Most likely, this event is a nu _{tau } CC interaction with charm production, the tau and charm particle decaying into 1 prong and 2 prongs, respectively. The significance of this observation is evaluated.

Investigation of abnormal absorption of cosmic-ray hadrons in lead calorimeters

A phenomenon of abnormally weak absorption of very high energy cosmic ray hadrons in thick lead blocks is discussed. This phenomenon was first observed in a Tien Shan high altitude experiment to study hadronic cores of extensive air showers (EAS) with a deep ionization calorimeter and encouraged researchers to introduce the hypothesis of the so-called long-flying or penetrating cosmic ray component. A similar effect was detected later with deep uniform lead X-ray emulsion chambers (XREC) at the Pamirs, which we discuss in detail. To establish the nature of the phenomenon we are have carried out dedicated experiments at the Tien Shan and at the Pamirs by exposing two-storey XRECs with large air gaps. According to detailed simulation of the chamber response, these experiments are very sensitive to the production of charmed hadrons in the forward kinematic region and can prove a hypothesis that the phenomenon under study can be explained on the assumption of very high values of charm particle production cross section at 〈ELab〉 ~ 75 TeV in the forward kinematic region at xLab≳ 0.1 which are near the upper limit of recent results of collider experiments, i.e., σpp→c¯c~ 8 mb. The same factor makes it possible to fit all the features of the experimental hadron absorption curve observed by means of deep uniform lead XRECs, including its bending at a depth of ~ 70 c.u.

Open charm measurements with the NA61/SHINE experiment at the CERN SPS

The strong interactions programme of the NA61/SHINE experiment at the CERN SPS has been extended through the use of new silicon Vertex Detector, which allows for reconstructing open charm particles. The detector was designed to identify those particles by means of a precise reconstruction of their primary and secondary vertices.An initial version of the Vertex Detector, called SAVD (Small Acceptance Vertex Detector), was installed end of 2016. It was operated in a Pb+Pb calibration beam time in 2016, and with Xe+La in 2017. A further Pb+Pb beam time is scheduled for late 2018. The first indications of a D0 peak were observed in the data obtained from the 2016 Pb+Pb run.This work introduces the physics motivation behind the open charm measurements, and the status of the analysis of the collected data on open charm production. Moreover, the plans of future open charm measurements in NA61/SHINE experiment and the related to upgrades of the vertex detector will be discussed.

Status of the vertex detector program of the CBM experiment at FAIR

The Compressed Baryonic Matter Experiment (CBM) is one of the core experiments of the future FAIR facility (Darmstadt/Germany). The fixed-target experiment will explore the phase diagram of strongly interacting matter in the regime of high net baryon densities with numerous rare probes. The Micro Vertex Detector (MVD) will determine the secondary decay vertex of open charm particles with $\sim 50~\rm \mu m$ precision, contribute to the background rejection in dielectron spectroscopy, and help to reconstruct neutral decay products of strange particles by means of missing mass identification. The MVD comprises four stations with 0.3 and $0.5\%~x/X_0$, which are placed between $5$ and $20~\rm cm$ downstream the target and inside vacuum. It will host highly-granular, next-generation Monolithic Active Pixel Sensors, with a spatial precision of $5\rm~\mu m$, a time resolution of $5 ~\rm \mu s$, and a peak rate capability of $\sim 700~\rm kHz/mm^2$. Moreover, a tolerance to $3\cdot10^{13}~\rm n_{eq}/cm^{2}$ and $\gtrsim 3~\rm Mrad$ are required. In this document, we summarize the status of sensor development, station prototyping, and the detector slow control.

The Small Acceptance Vertex Detector of NA61/SHINE

Charmonium production in heavy ion collisions is considered as an important diagnostic probe for studying the phase diagram of strongly interacting matter for potential phase transitions. The interpretation of existing data from the CERN SPS is hampered by a lack of knowledge on the properties of open charm particle production in the fireball. Moreover, open charm production in heavy ion collisions by itself is poorly understood. To overcome this obstacle, the NA61/SHINE was equipped with a Small Acceptance Vertex Detector (SAVD), which is predicted to make the experiment sensitive to open charm mesons produced in A-A collisions at the SPS top energy. This paper will introduce the concept and the hardware of the SAVD. Moreover, first running experience as obtained in a commissioning run with a 150 AGeV/c Pb+Pb collision system will be reported.

The Small Acceptance Vertex Detector of NA61/SHINE

Charmonium production in heavy ion collisions is considered as an important diagnostic probe for studying the phase diagram of strongly interacting matter for potential phase transitions. The interpretation of existing data from the CERN SPS is hampered by a lack of knowledge on the properties of open charm particle production in the fireball. Moreover, open charm production in heavy ion collisions by itself is poorly understood. To overcome this obstacle, the NA61/SHINE was equipped with a Small Acceptance Vertex Detector (SAVD), which is predicted to make the experiment sensitive to open charm mesons produced in A-A collisions at the SPS top energy. This paper will introduce the concept and the hardware of the SAVD. Moreover, first running experience as obtained in a commissioning run with a 150 AGeV/c Pb+Pb collision system will be reported.

Open Charm Production in Central Pb+Pb Collisions at the CERN SPS: Statistical Model Estimates

Charm particle production in nucleus-nucleus collisions at the CERN SPS energies is considered within a statistical approach. Namely, the Statistical Model of the Early Stage is used to calculate mean multiplicity of charm particles in central Pb+Pb collisions. A small number of produced charm particles necessitates the use of the exact charm conservation law. The model predicts a rapid increase of mean charm multiplicity as a function of collision energy. The mean multiplicity calculated for central Pb+Pb collisions at the center of mass energy per nucleon pair $\sqrt{s_{NN}}=17.3$ GeV exceeds significantly the experimental upper limit. Thus, in order to describe open charm production model parameters and/or assumptions should be revised.

A brief review of measurements of electroweak bosons at the LHCb experiment in LHC Run 1

The LHCb experiment is one of four major experiments at the large hadron collider (LHC). Despite being designed for the study of beauty and charm particles, it has made important contributions in other areas, such as the production and decay of W and Z bosons. Such measurements can be used to study and constrain parton distribution functions (PDFs), as well as to test perturbative quantum chromodynamics (QCD) in hard scattering processes. The angular structure of Z boson decays to leptons can also be studied and used to measure the weak mixing angle. The phase–space probed by LHCb is particularly sensitive to this quantity, and the LHCb measurement using the dimuon final state is currently the most precise determination of [Formula: see text] at the LHC. LHCb measurements made using data collected during the first period of LHC operations (LHC Run 1) are discussed in this review. The paper also considers the potential impact of related future measurements.

Charm contribution to the atmospheric neutrino flux

We revisit the estimate of the charm particle contribution to the atmospheric neutrino flux that is expected to dominate at high energies because long-lived high-energy pions and kaons interact in the atmosphere before decaying into neutrinos. We focus on the production of forward charm particles which carry a large fraction of the momentum of the incident proton. In the case of strange particles, such a component is familiar from the abundant production of $K^{+} \Lambda$ pairs. These forward charm particles can dominate the high-energy atmospheric neutrino flux in underground experiments. Modern collider experiments have no coverage in the very large rapidity region where charm forward pair production dominates. Using archival accelerator data as well as IceCube measurements of atmospheric electron and muon neutrino fluxes, we obtain an upper limit on forward $\bar{D}^0 \Lambda_c$ pair production and on the associated flux of high-energy atmospheric neutrinos. We conclude that the prompt flux may dominate the much-studied central component and represent a significant contribution to the TeV atmospheric neutrino flux. Importantly, it cannot accommodate the PeV flux of high-energy cosmic neutrinos, nor the excess of events observed by IceCube in the 30--200 TeV energy range indicating either structure in the flux of cosmic accelerators, or a presence of more than one component in the cosmic flux observed.

The PANDA Barrel DIRC

The PANDA detector at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR) addresses fundamental questions of hadron physics. Experiments concerning charmonium spectroscopy, the search for hybrids and glueballs and the interaction of hidden and open charm particles with nucleons and nuclei will be performed with antiproton beams impinging on hydrogen or nuclear targets. Cooled beams allow the precision scan of resonances in formation experiments. The momentum range of the antiproton beam between 1.5 GeV/c and 15 GeV/c tests predictions by perturbation theory and will reveal deviations originating from strong QCD . An excellent hadronic particle identification will be accomplished by DIRC (Detection of Internally Reflected Cherenkov light) counters. The design for the barrel region is based on the successful BaBar DIRC with several key improvements, such as fast photon timing and a compact imaging region. DIRC designs based on different radiator geometries with several focusing options were studied in simulation. The performance of each design was characterized in terms of photon yield and single photon Cherenkov angle resolution. Selected design options were implemented in prototypes and tested with hadronic particle beams at GSI and CERN.

Tracking parameter simulation for the Turkish accelerator center particle factory tracker system

The silicon tracker part of the Turkish Accelerator Center super charm particle factory detector was designed for effectively tracking charged particles with momentum values up to 2.0GeV/c. In this work, the FLUKA simulation code has been used to estimate the track parameters and their resolutions in the designed tracker system. These results have been compared with those obtained by the tkLayout software package. The simulated track parameter resolutions are compatible with the physics goals of the tracking detector.

Constraints on atmospheric charmed-meson production from IceCube

At very-high energies (100 TeV - 1 PeV), the small value of Bjorken-x ($\le10^{-3}-10^{-7}$) at which the parton distribution functions are evaluated makes the calculation of charm quark production very difficult. The charm quark has mass ($\sim$1.5$\pm$0.2 GeV) significantly above the $\Lambda$$_{QCD}$ scale ($\sim$200 MeV), and therefore its production is perturbatively calculable. However, the uncertainty in the data and the calculations cannot exclude some smaller non-perturbative contribution. To evaluate the prompt neutrino flux, one needs to know the charm production cross-section in pN -> c$\bar{c}$ X, and hadronization of charm particles. This contribution briefly discusses computation of prompt neutrino flux and presents the strongest limit on prompt neutrino flux from IceCube.

High-energy behavior of photon, neutrino, and proton cross sections

By combining the color dipole model of the nucleon with the assumption that cross sections behave asymptotically as $\ln^2(s)$, we are able to describe the data for photon, neutrino and hadron interactions with protons at all energies, $s$ is the center-of-mass energy of the interacting particles. Specifically, we extrapolate the perturbative QCD calculations into the regime of small fractional parton momenta $x$ using a color dipole description of the proton target that guarantees an asymptotic $\ln^2(s)$ behavior of all cross sections. The ambiguity of introducing a parametrization associated with the dipole approximation is mitigated by the requirement that the saturation of the small-$x$ structure functions produces $\ln^2(s)$-behaved asymptotic cross sections, in agreement with the data. The same formalism allows us to calculate the cross section for the hadronic pair production of charm particles. The results, in particular those for the high-energy neutrino and charm cross sections, are relevant for evaluating the sensitivity as well as the background in neutrino telescopes.