Search

The Scattering and Neutrino Detector at the LHC (SND@LHC) started taking data at the beginning of Run 3 of the LHC. The experiment is designed to perform measurements with neutrinos produced in proton-proton collisions at the LHC in an energy range between 100 GeV and 1 TeV. It covers a previously unexplored pseudo-rapidity range of 7.2 < η < 8.4 . The detector is located 480 m downstream of the ATLAS interaction point in the TI18 tunnel. It comprises a veto system, a target consisting of tungsten plates interleaved with nuclear emulsion and scintillating fiber (SciFi) trackers, followed by a muon detector (UpStream, US and DownStream, DS). In this article we report the measurement of the muon flux in three subdetectors: the emulsion, the SciFi trackers and the DownStream Muon detector. The muon flux per integrated luminosity through an 18 × 18 cm 2 area in the emulsion is: 1.5 ± 0.1 (stat) × 10 4 fb/cm 2. The muon flux per integrated luminosity through a 31 × 31 cm 2 area in the centre of the SciFi is: 2.06 ± 0.01 (stat) ± 0.12 (sys) × 10 4 fb/cm 2 The muon flux per integrated luminosity through a 52 × 52 cm 2 area in the centre of the downstream muon system is: 2.35 ± 0.01 (stat) ± 0.10 (sys) × 10 4 fb/cm 2 The total relative uncertainty of the measurements by the electronic detectors is 6 % for the SciFi and 4 % for the DS measurement. The Monte Carlo simulation prediction of these fluxes is 20–25 % lower than the measured values. [ABSTRACT FROM AUTHOR]

Abstract The transcriptome needs to be tightly regulated by mechanisms that include transcription factors, enhancers, and repressors as well as non‐coding RNAs. Besides this dynamic regulation, a large part of phenotypic variability of eukaryotes is expressed through changes in gene transcription caused by genetic variation. In this study, we evaluate genome‐wide structural genomic variants (SVs) and their association with gene expression in the human heart. We detected 3,898 individual SVs affecting all classes of gene transcripts (e.g., mRNA, miRNA, lncRNA) and regulatory genomic regions (e.g., enhancer or TFBS). In a cohort of patients (n = 50) with dilated cardiomyopathy (DCM), 80,635 non‐protein‐coding elements of the genome are deleted or duplicated by SVs, containing 3,758 long non‐coding RNAs and 1,756 protein‐coding transcripts. 65.3% of the SV‐eQTLs do not harbor a significant SNV‐eQTL, and for the regions with both classes of association, we find similar effect sizes. In case of deleted protein‐coding exons, we find downregulation of the associated transcripts, duplication events, however, do not show significant changes over all events. In summary, we are first to describe the genomic variability associated with SVs in heart failure due to DCM and dissect their impact on the transcriptome. Overall, SVs explain up to 7.5% of the variation of cardiac gene expression, underlining the importance to study human myocardial gene expression in the context of the individual genome. This has immediate implications for studies on basic mechanisms of cardiac maladaptation, biomarkers, and (gene) therapeutic studies alike.

High-precision measurements of flow coefficients v n ( n = 1 - 4 ) for protons, deuterons and tritons relative to the first-order spectator plane have been performed in Au+Au collisions at s NN = 2.4 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at the SIS18/GSI. Flow coefficients are studied as a function of transverse momentum p t and rapidity y cm over a large region of phase-space and for several classes of collision centrality. A clear mass hierarchy, as expected by relativistic hydrodynamics, is found for the slope of v 1 , d v 1 / d y ′ | y ′ = 0 where y ′ is the scaled rapidity, and for v 2 at mid-rapidity. Scaling with the number of nucleons is observed for the p t dependence of v 2 and v 4 at mid-rapidity, which is indicative for nuclear coalescence as the main process responsible for light nuclei formation. v 2 is found to scale with the initial eccentricity ⟨ ϵ 2 ⟩ , while v 4 scales with ⟨ ϵ 2 ⟩ 2 and ⟨ ϵ 4 ⟩ . The multi-differential high-precision data on v 1 , v 2 , v 3 , and v 4 provides important constraints on the equation-of-state of compressed baryonic matter. [ABSTRACT FROM AUTHOR]

In nuclear collisions the incident protons generate a Coulomb field which acts on produced charged particles. The impact of these interactions on charged-pion transverse-mass and rapidity spectra, as well as on pion–pion momentum correlations is investigated in Au + Au collisions at s NN = 2.4 GeV. We show that the low- m t region ( m t < 0.2 GeV/ c 2 ) can be well described with a Coulomb-modified Boltzmann distribution that also takes changes of the Coulomb field during the expansion of the fireball into account. The observed centrality dependence of the fitted mean Coulomb potential energy deviates strongly from a A part 2 / 3 scaling, indicating that, next to the fireball, the non-interacting charged spectators have to be taken into account. For the most central collisions, the Coulomb modifications of the HBT source radii are found to be consistent with the potential extracted from the single-pion transverse-mass distributions. This finding suggests that the region of homogeneity obtained from two-pion correlations coincides with the region in which the pions freeze-out. Using the inferred mean-square radius of the charge distribution at freeze-out, we have deduced a baryon density, in fair agreement with values obtained from statistical hadronization model fits to the particle yields. [ABSTRACT FROM AUTHOR]

We present high-statistic data on charged-pion emission from Au + Au collisions at s NN = 2.4 GeV (corresponding to E beam = 1.23 A GeV ) in four centrality classes in the range 0–40% of the most central collisions. The data are analyzed as a function of transverse momentum, transverse mass, rapidity, and polar angle. Pion multiplicity per participating nucleon decreases moderately with increasing centrality. The polar angular distributions are found to be non-isotropic even for the most central event class. Our results on pion multiplicity fit well into the general trend of the available world data, but undershoot by 2.5 σ data from the FOPI experiment measured at slightly lower beam energy. We compare our data to state-of-the-art transport model calculations (PHSD, IQMD, PHQMD, GiBUU and SMASH) and find substantial differences between the measurement and the results of these calculations. [ABSTRACT FROM AUTHOR]

High-statistics π - π - and π + π + femtoscopy data are presented for Au + Au collisions at s NN = 2.4 GeV , measured with HADES at SIS18/GSI. The experimental correlation functions allow the determination of the space-time extent of the corresponding emission sources via a comparison to models. The emission source, parametrized as three-dimensional Gaussian distribution, is studied in dependence on pair transverse momentum, azimuthal emission angle with respect to the reaction plane, collision centrality and beam energy. For all centralities and transverse momenta, a geometrical distribution of ellipsoidal shape is found in the plane perpendicular to the beam direction with the larger extension perpendicular to the reaction plane. For large transverse momenta, the corresponding eccentricity approaches the initial eccentricity. The eccentricity is smallest for most central collisions, where the shape is almost circular. The magnitude of the tilt angle of the emission ellipsoid in the reaction plane decreases with increasing centrality and increasing transverse momentum. All source radii increase with centrality, largely exhibiting a linear rise with the cube root of the number of participants. A substantial charge-sign difference of the source radii is found, appearing most pronounced at low transverse momentum. The extracted source parameters are consistent with the extrapolation of their energy dependence down from higher energies. [ABSTRACT FROM AUTHOR]

The combination of a production target for secondary beams, an optimized ion optical beam line setting, in-beam detectors for minimum ionizing particles with high rate capability, and an efficient large acceptance spectrometer around the reaction target constitutes an experimental opportunity to study in detail hadronic interactions utilizing pion beams impinging on nucleons and nuclei. For the 0.4-2.0GeV/c pion momentum regime such a facility is located at the heavy ion synchrotron accelerator SIS18 in Darmstadt (Germany). The layout of the apparatus, performance of its components and encouraging results from a first commissioning run are presented. [ABSTRACT FROM AUTHOR]

We report on the investigation of dielectron production in tagged quasi-free neutron-proton collisions by using a deuteron beam of kinetic energy 1.25GeV/u impinging on a liquid hydrogen target. Our measurements with HADES confirm a significant excess of $e^{+}e^{-}$ pairs above the $\pi^{0}$ mass in the exclusive channel $dp \rightarrow npe^{+}e^{-}(p_{spect})$ as compared to the exclusive channel $ ppe^{+}e^{-}$ measured in proton-proton collisions at the same energy. That excess points to different bremsstrahlung production mechanisms. Two models were evaluated for the role of the charged pion exchange between nucleons and double- $\Delta$ excitation combined with intermediate $\rho$ -meson production. Differential cross sections as a function of the $e^{+}e^{-}$ invariant mass and of the angles of the virtual photon, proton and electrons provide valuable constraints and encourage further investigations on both experimental and theoretical sides. [ABSTRACT FROM AUTHOR]

Large samples of Λ, Σ(1385) and Ξ(1321) hyperons produced in the deep-inelastic muon scattering off a 6LiD target were collected with the COMPASS experimental setup at CERN. The relative yields of Σ(1385) +, Σ(1385) −, $\bar{\varSigma}(1385)^{-}$ , $\bar{\varSigma}(1385)^{+}$ , Ξ(1321) −, and $\bar{\varXi}(1321)^{+}$ hyperons decaying into $\varLambda(\bar{\varLambda})\pi$ were measured. The ratios of heavy-hyperon to Λ and heavy-antihyperon to $\bar{\varLambda}$ were found to be in the range 3.8 % to 5.6 % with a relative uncertainty of about 10 %. They were used to tune the parameters relevant for strange particle production of the LEPTO Monte Carlo generator. [ABSTRACT FROM AUTHOR]

zimuthal asymmetries in semi-inclusive production of positive ( h) and negative hadrons ( h) have been measured by scattering 160 GeV muons off longitudinally polarised deuterons at CERN. The asymmetries were decomposed in several terms according to their expected modulation in the azimuthal angle φ of the outgoing hadron. Each term receives contributions from one or several spin and transverse-momentum-dependent parton distribution and fragmentation functions. The amplitudes of all φ-modulation terms of the hadron asymmetries integrated over the kinematic variables are found to be consistent with zero within statistical errors, while the constant terms are nonzero and equal for h and h within the statistical errors. The dependencies of the φ-modulated terms versus the Bjorken momentum fraction x, the hadron fractional momentum z, and the hadron transverse momentum $p_{h}^{T}$ were studied. The x dependence of the constant terms for both positive and negative hadrons is in agreement with the longitudinal double-spin hadron asymmetries, measured in semi-inclusive deep-inelastic scattering. The x dependence of the sin φ-modulation term is less pronounced than that in the corresponding HERMES data. All other dependencies of the φ-modulation amplitudes are consistent with zero within the statistical errors. [ABSTRACT FROM AUTHOR]

The J/ ψ azimuthal distribution relative to the reaction plane has been measured by the NA50 experiment in Pb-Pb collisions at 158 GeV/nucleon. Various physical mechanisms related to charmonium dissociation in the medium created in the heavy ion collision are expected to introduce an anisotropy in the azimuthal distribution of the observed J/ ψ mesons at SPS energies. Hence, the measurement of J/ ψ elliptic anisotropy, quantified by the Fourier coefficient v2 of the J/ ψ azimuthal distribution relative to the reaction plane, is an important tool to constrain theoretical models aimed at explaining the anomalous J/ ψ suppression observed in Pb-Pb collisions. We present the measured J/ ψ yields in different bins of azimuthal angle relative to the reaction plane, as well as the resulting values of the Fourier coefficient v2 as a function of the collision centrality and of the J/ ψ transverse momentum. The reaction plane has been estimated from the azimuthal distribution of the neutral transverse energy detected in an electromagnetic calorimeter. The analysis has been performed on a data sample of about 100 000 events, distributed in five centrality or pT sub-samples. The extracted v2 values are significantly larger than zero for non-central collisions and are seen to increase with pT. [ABSTRACT FROM AUTHOR]

The longitudinal double spin asymmetry A1 ρ for exclusive leptoproduction of ρ0 mesons, μ+N→μ+N+ρ, is studied using the COMPASS 2002 and 2003 data. The measured reaction is incoherent exclusive ρ0 production on polarised deuterons. The Q2 and x dependence of A1 ρ is presented in a wide kinematical range, 3×10-32< 7 (GeV/ c)2 and 5×10-51 ρ at small Q2 (Q2< 0.1 (GeV/ c)2) and small x (x<3×10-3). The asymmetry is in general compatible with zero in the whole kinematical range. [ABSTRACT FROM AUTHOR]

ψ′ production is studied in Pb–Pb collisions at 158 GeV/c per nucleon incident momentum. Absolute cross-sections are measured and production rates are investigated as a function of the centrality of the collision. The results are compared with those obtained for lighter colliding systems and also for the J/ψ meson produced under identical conditions. [ABSTRACT FROM AUTHOR]

We report a new measurement of J/ψ, ψ′ and Drell–Yan cross-sections, in the kinematical domain -0.425cm<0.575 and -0.5CS<0.5, performed at the CERN-SPS using 400 GeV/c incident protons on Be, Al, Cu, Ag, W and Pb targets. The dependence of the charmonia production cross-sections on the size of the target nucleus allows to quantify the so-called normal nuclear absorption. In the framework of the Glauber model, this new measurement is combined with results previously obtained with the same apparatus, under different experimental conditions, and leads to a precise determination of the J/ψ and ψ′ absorption cross-sections in the surrounding nuclear matter. [ABSTRACT FROM AUTHOR]

We present a new measurement ofproduction in Pb-Pb collisions at 158 GeV/nucleon, from the data sample collected in year 2000 by the NA50 Collaboration, under improved experimental conditions with respect to previous years. With the target system placed in vacuum, the setup was better adapted to study, in particular, the most peripheral nuclear collisions with unprecedented accuracy. The analysis of this data sample shows that thecross-sections ratio measured in the most peripheral Pb-Pb interactions is in good agreement with the nuclear absorption pattern extrapolated from the studies of proton-nucleus collisions. Furthermore, this new measurement confirms our previous observation that thecross-sections ratio departs from the normal nuclear absorption pattern for semi-central Pb-Pb collisions and that this ratio persistently decreases up to the most central collisions. [ABSTRACT FROM AUTHOR]

The NA50 experiment at CERN SPS has studied charmonium production in Pb−Pb collisions at 158 GeV/c per nucleon. According to the theoretical predictions the observation of the suppression of the J/ψ production yield is expected to be an unambiguous probe for a phase transition from ordinary nuclear matter towards a state in which quarks and gluons are deconfined. [ABSTRACT FROM AUTHOR]

The production of J/Ψand &Psi′ charmonium states in proton-nucleus interactions has been investigated by the NA50 experiment, at the CERN SPS. High statistics data sets were collected with collisions induced by 450 GeV protons incident on Be, Al, Cu, Ag and W targets. The J/ψand ψ production cross-sections have been determined for each p-A system and their dependences on the nucleus size have been studied, leading to the so-called normal nuclear absorption. Comparing the two patterns we see that the nuclear absorption is stronger for the &Psi′ than for the J/Ψ. Given the high statistics of the data samples, the xF (or rapidity) differential cross-sections of the J/Ψ and &Psi′ states have also been studied, for each of the target nuclei. [ABSTRACT FROM AUTHOR]

The NA50 experiment at CERN SPS has been equipped with a quartz Cherenkov detector to measure the charge of projectile-like fragments emitted in interactions of the lead beam of 158 AGeV with a lead target. A fission peak has been observed in the light output distribution of the fragment detector. The information provided by the NA50 zero-degree calorimeter indicates that fission occurs in extremely peripheral collisions, compatible (within the resolution of the detector) with electromagnetic interaction. The expected yield of Coulomb fission events in our experimental condition has been evaluated and turns out to be about 40% smaller than the observed one. [ABSTRACT FROM AUTHOR]

Meson production in proton, oxygen and sulphur interactions with uranium targets at 200 GeV/nucleon is studied. We measure the inclusive meson cross-section d σ/d P and its evolution from p+U to S+U. The cross-section fitted with an exponential gives an inverse slope P of the order of 210 MeV/c. As a function of the neutral transverse energy, P values show a slight rise followed by a plateau. The normalized difference (σ−σ)/σ between positive and negative meson cross-sections is found to increase with E. [ABSTRACT FROM AUTHOR]

We present a study of $$B\bar B$$ meson pair production in π interactions at 140, 194 and 286 GeV incident pion energy. At 286 GeV, where we have the best statistics, we find a model-dependent $$B\bar B$$ production cross-section $$\sigma _{BB} = 14_{ - 6}^{ + 7} nb/nucleon$$ . [ABSTRACT FROM AUTHOR]

The dimuon production in 200 GeV/nucleon oxygen-uranium interactions is studied by the NA 38 Collaboration. The production of J/ψ, correlated with the transverse energy ET, is investigated and compared to the continuum, as a function of the dimuon mass M and transverse momentum PT. A value of 0.64±0.06 is found for the ratio (ψ/Continuum at high ET)/(ψ/Continuum at low ET), from which the J/ψ relative suppression can be extracted. This suppression is enhanced at low PT. [ABSTRACT FROM AUTHOR]

The like-sign dimuons copiously recorded in the NA 38 experiment both in p-U and O−U reactions at 200 GeV/nucleon are interpreted as resulting from decays of π and K mesons in comparable proportions. The ++/−− ratio is large (≃1.7) and ascribed to the K being more copiously produced than the K. Both the average transverse momentum and the ++/−− ratio are comparable for p-U and O−U reactions, and both increase only slightly with the transverse energy E. [ABSTRACT FROM AUTHOR]

We present the angular distributions of high-mass muon pairs produced in a high-statistics experiment by 140 and 194 GeV/c π beams impinging on a tungsten target, and by 286 GeV/c π beam on deuterium and tungsten targets. We find no evidence for a center-of-mass energy dependence or a nuclear dependence of the angular distribution parameters. The two parameters λ and μ are found to be essentially independent of any kinematical variable. In contrast, the parameter v increase with the dimuon transverse momentum P, at variance with recent perturbative QCD predictions. Our statistics at large x are insufficient to substantiate the highertwist prediction. [ABSTRACT FROM AUTHOR]

We present the angular distributions of muon pairs obtained in a high-statistics experiment using a 194-GeV/c π impinging on a tungsten target. Our results are based on the analysis of 145,000 events with positive Feynman x and mass above 4.07 GeV/c, excluding the ϒ region. Simple first-order QCD relations allow us to determine the ratio of annihilation with hard-gluon emission to the sum of annihilation with hard-gluon emission and hard-gluon Compton scattering, which is found to be about 58% to 75%. We determine the parton square intrinsic transverse momenta to be of the order of 0.6 (GeV/c), and about 30% larger in the pion than in the nucleon. At large x, our data agree with the higher-twist hypothesis, and support the interpretation of the relevant scale parameter as the dimuon square transverse momentum. [ABSTRACT FROM AUTHOR]

We present a measurement of the production of muon pairs in 194 GeV/c π-tungsten interactions. A sample of 155,000 events with mass higher than 4.07 GeV/c has been used to determine the differential cross-section as a function of the scaling variables $$\sqrt \tau $$ and x. [ABSTRACT FROM AUTHOR]

The differential cross-section for dimuon production by 194 GeV/c π on W, as measured by the NA10 Collaboration, is compared with theoretical models. The wide kinematical range of the data, extending well above the ϒ resonances, provides the opportunity of a comparison with 'realistic' Drell-Yan models, i.e. with those allowing for scaling violation in the hadronic structure functions. The data in fact clearly indicate the failure of the 'naïve' Drell-Yan model, while the available 'realistic' versions (leading logarithm approximation and next-to-leading logarithm approximation in first order QCD), although giving a better description of the data, still disagree in the x and $$\sqrt \tau $$ dependences of the cross-section at high dimuon masses. This disagreement is referred to here as 'anomalous' scaling violation. The dependence of the results on external inputs (nucleon and pion-sea structure functions) is analysed; it is shown that in the next-to-leading logarithm approximation the value 〈 K〉=1.03±0.03 (stat.) can be obtained for the ratio experimental/theoretical cross-section. [ABSTRACT FROM AUTHOR]

The production of low mass dimuons has been measured in d-C, d-U and S-U collisions at 200 GeV per nucleon, and in Pb-Pb collisions at 160 GeV per nucleon. The ϕ, ρ and ω productions in S-U collision [1, 2] are extracted from a new set of data with increased statistic, and are through ϕ/(ω+ρ) ratio compared to first results on deuteron induced production. These new analyses are presented in the limited M domain of recent Pb-Pb measurement whose preliminary results are also presented. [ABSTRACT FROM AUTHOR]

The centrality determination for Au + Au collisions at 1.23A GeV, as measured with HADES at the GSI-SIS18, is described. In order to extract collision geometry related quantities, such as the average impact parameter or number of participating nucleons, a Glauber Monte Carlo approach is employed. For the application of this model to collisions at this relatively low centre-of-mass energy of s NN =2.42 GeV special investigations were performed. As a result a well defined procedure to determine centrality classes for ongoing analyses of heavy-ion data is established. [ABSTRACT FROM AUTHOR]