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Slides of the lectures proposed during the pre-conference school, which took place on Sunday afternoon.
Inferences About the Equation of State from Gravitational Waves and NICER
First results from Belle II
Dilepton production in heavy-ion collisions
...
Run 1 and Run 2 of the Large Hadron Collider (LHC) at CERN produced huge volumes of data whose analysis will continue to deliver large numbers of physics results. To make this possible, the LHC experiments have been relying on services of the Worldwide LHC Computing Grid (WLCG).
At present, the LHC experiments are preparing for Run 3 of the LHC which will bring significantly higher luminosity and therefore yet higher volumes of data, which will even be exceeded in the era of the High Luminosity LHC (HL-LHC), starting with Run 4.
While during Run 1 and Run 2 the LHC experiments were the only ones to produce and analyze scientific data at a scale of hundreds of petabytes, the situation is gradually changing. Projects like DUNE in the USA, Belle II in Japan and SKA in Australia and South Africa will also be producing huge volumes of data and plan to make significant use of WLCG services to store and process their data. The LHC experiments will not necessarily remain the biggest scientific data producers in the future.
In this contribution we will present an overview of trends and strategies used by the LHC experiments to adapt their data processing models to future compute and storage resources available within WLCG and to the use of commercial clouds and High Performance Computing (HPC) facilities, while at the same time building collaborations with related big-data projects in order to share and evolve WLCG services together.
Heavy-ion collisions covering a wide range of collision energies provide a vast amount of observables characterizing the properties of strongly-interacting matter. In particular collisions towards the high baryon-density regime of the QCD phase diagram have become of interest to study the phase transition between hadronic and partonic matter and to locate a possible critical end point. To correctly interpret the obtained experimental results, accurate theoretical models are essential. In this talk, a novel hybrid model is presented, which applies the SMASH transport approach for the description of hadronic matter in the initial and final state and the 3+1D vHLLE viscous hydrodynamics code for the description of the equilibrated fireball. The hydrodynamic evolution is initialized dynamically from the transport evolution and the resulting source terms are consistently taken into consideration.
As a first step, the particle production for different collision energies is compared to experimental data and the implications for electromagnetic oberservables are discussed. In addition, phase transition observables are explored for varying equations of state.
Past experiments have revealed discrepancies in the consistency of the data from neutron form factor measurements, suffering from systematic uncertainty of the neutron detection. Measurements of the neutron's magnetic form factor $G^n_M$ suffer from insufficient detection efficiency whereas measurements of the neutron's electric form factor $G^n_E$ suffer from large backgrounds and low statistics. To overcome these shortcomings, a high rate neutron polarimeter has been developed by the A1 collaboration at the Institute for Nuclear Physics in Mainz, Germany extending their three-spectrometer apparatus at MAMI. It will measure $G^n_E$ over a large range of momentum transfers of $0.2 < Q^2 < 1.6 \text{ GeV}^2$ with consistent settings via double-polarized electron-deuterium quasi-elastic scattering. To reach an unprecedented statistical accuracy and high detection efficiency, the polarimeter must cope with several Mcps of background while providing precise timing of significantly less than 500 ps for position measurements as well as neutron time-of-flight measurements to deduce their momentum. In combination with a high resolution magnetic spectrometer analyzing the momentum of the scattered electrons, the reaction's kinematics can be precisely reconstructed. To meet the high rate capability and timing precision requirements, the signals of the plastic scintillators are discriminated by custom-made front-end electronics based on the ultrafast multi-channel NINO ASIC, encoding the signal time-over-threshold into the output signal width. Digitization is performed by TRB3 boards with multi-hit capability covering a total of 574 channels. Their FPGA-based high precision TDCs measure leading as well as trailing edges of the NINO output signals with negligible dead time and hardware resources compared with conventional ADCs or sampling ASICs. The precise time-over-threshold information allows walk corrections and background suppression by reconstructing the signal amplitudes to deduce the related energy deposits. In April 2019, the first pilot experiment at a momentum transfer of $0.6 \text{ GeV}^2$ has been performed. Preliminary results will be discussed in January 2020 at the 58th International Winter Meeting on Nuclear Physics in Bormio, Italy.
The idea of adding an Electromagnetic CALorimeter to the HADES spectrometer came from an interest in photon measurement and consequentially the detection of neutral mesons and resonances via their decay in photon pairs. Another advantage of having ECAL in the system is a significant improvement of electron-pion separation at high momenta. The detector is based on lead-glass modules with a PMT read-out. The lead-glass acts both as the active volume for Cherenkov light generation and also as the medium for the development of the electromagnetic shower. As in any new detection system, the commissioning brought some unexpected challenges. The challenges were connected both with readout electronics and with the assembly of magnetic shielding and PMT. This talk will mainly focus on the commissioning in general and on a solution to the troubles with PMT and magnetic shielding. The symptoms will be shown and the reason and solution will be discussed in detail.
Cold-matter and hot-medium effects in p-Pb collisions at LHC energies - Hung
The high collision energies reached at the LHC lead to significant production
yields of light (anti-)nuclei in proton-proton and, in
particular, Pb-Pb collisions. The excellent particle identification capabilities
of the ALICE Time Projection Chamber using the measurement of the specific energy
loss (dE/dx) and the time of flight allow for the
detection of these rarely produced particles.
Recent results on (anti-)triton and (anti-)4He production in Pb-Pb collisions at sqrt(s_NN)=5.02 TeV will be presented and compared to coalescence and statistical hadronization models to provide insight into their production mechanism in heavy-ion collisions.
The recently developed renormalization group improved optimized perturbation theory (RGOPT) is applied to QCD at zero temperatures and finite densities. The pressure for cold and dense quark matter is calculated as a first application of this technique to QCD in the presence of a control parameter. At leading order a non-perturbative and completely scale invariant result is found. At next-to leading order the RGOPT shows a very good agreement with the state of the art higher order perturbative results. Also, at this two loop order the RGOPT results are less sensitive to the variations of the renormalization scale than the ones obtained with perturbative QCD. Our results indicate that this non perturbative approximation is a robust alternative to treat QCD in the regime of high baryonic densities, which is currently unavailable to lattice simulations.
Investigations of few-nucleon systems provide suitable testing ground for different models of the nucleon-nucleon interaction. In three-nucleon systems, at intermediate energy, below the pion production threshold, the effects of three-nucleon forces (3NF) are generally small and hard for experimental study. To take a step forward into larger system, a four-nucleon (4N) were studied, where sensitivity to the 3NF effects becomes higher. Recently, the development of the 4N system calculations became a hot topic in theoretical nuclear physics. The Vilnus-Lisbon group calculates observables for multichannel reactions, also above the breakup threshold, and with the Coulomb force included [1].
Experiment devoted to studies of deuteron breakup reactions were carried out at KVI in Groningen (The Netherlands) with the use of the BINA detector and 160 MeV deuteron beam on deuteron target. The experiment is a continuation of previous very successful few-nucleon reaction studies [2, 3]. The aim of this analysis was to study two kinds of reaction, three-body 2H(d,dp)n deuteron breakup and the transfer reaction 2H(d,3He)n. The differential cross section of breakup reaction can be confronted with the newest calculation for the deuteron-deuteron system based on so-called Single-Scattering-Approximation (SSA). Recently developed techniques allows us to identify the neutrons in the BINA detection systems. This gives us possibility to study also the breakup reaction in a channel with direct neutron detection. Having determine the differential cross sections for both,2H(d,dp)n and 2H(d,dn)p three-body breakup channels one can compare it at the same kinematic conditions and directly study the Coulomb effects and possible charge symmetry breaking, like it was suggested in [5].
In this contribution I will show the results of the study of the deuteron-deuteron system with the use of BINA setup at 160 MeV. A set of data for differential cross section of the 2H(d,dp)n breakup [6] and 2H(d,3He)n transfer [7] reaction will be presented. In addition the preliminary results of the neutron detection method and the differential cross section of the 2H(d,dn)p will be outlined.
References
[1] A. Deltuva, A. C. Fonseca, Phys. Rev. C 95 (2017) 024003
[2] S. Kistryn, E. Stephan, J. Phys. G 40, (2013) 063101.
[3] I. Ciepal et al., Few-Body Syst. 56 (2015) 665
[4] G. Khatri et al., Acta Phys. Pol., B 47 (2016) 411
[5] C. R. Howell et al., Phys. Rev. C 48 (1993) 2855.
[6] I. Ciepal et al., Phys. Rev. C 99, (2019) 014620.
[7] I. Ciepal et al., Phys. Rev. C 100, (2019) 024003.
Exotic decays of atomic nuclei
Recent results of the LHC experiments ATLAS and CMS
Hyperon-nuclear interactions and strangeness in neutron stars
New physics with coherent neutrino-nucleus scattering
The KM3NeT project: status and future perspectives
A series of frontier experiments will be presented based on high sensitivity X-ray spectroscopy,aiming on one side to measure low-lying orbits transitions in exotic kaonic atoms at accelerators, on the other to unveil eventual signal from Pauli-violating atoms, predicted to be formed in theories beyond the Standard Model.
The first part of the talk will be dedicated to kaonic atoms studies in the framework of the SIDDHARTA experiment at the DAFNE Collider of LNF-INFN, Frascati (Roma) laboratory. The low energy kaon beam delivered by the DANE collider, combined with new experimental techniques, based on fast and high-resolution Silicon Drift Detectors (SDD), allowed unprecedented measurements on kaonic hydrogen and helium. Presently, a major upgrade of the setup, SIDDHARTA-2 is being realized to perform in the coming year(s) the first ever measurement of kaonic deuterium.Such experimental infomation is essential in the low-energy QCD in the sector ofthe strange quark, responsible for a delicate interplay among the spontaneous and explicit breaking of Chiral Symmetry.
In the second part of the talk the VIP-2 experiment will be presented. The SDDs based experimental apparatus is operated in the extremely low-background environment of the underground LNGS laboratory and aims to disclose eventual signal of non-Paulian Kalpha transitions in Copper atoms. The spin-statistics connection can be only demonstrated within Quantum Field Theory, on the basis of few assumptions which are intimately related to the same structure of space and time. Experimental evidence of evena tiny violation of the Pauli Exclusion Principle would be an indication of physics beyond the Standard Model.
The production of particles in heavy ion collisions is of great importance to inspect the properties and dynamics of hadronic matter. As part of the HADES experiment at GSI Ag+Ag collisions at beam energies of 1.58A GeV have been performed in spring 2019. In the light of these experimental studies this work provides a theoretical prediction of the expected results. The hadronic transport approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is applied in order to predict the production of particles (protons, pions, kaons) and their respective distributions in phase space. A special focus is given to the production rates of $\phi$ mesons and $\Xi^-$ baryons and their agreement with recent HADES data.
In addition to the analysis of multiplicities and rapidity spectra, the mean transverse masses for different centrality classes are explored. In this context the hadronic spectra are confronted with earlier HADES results for Au+Au and C+C collisions in order to study the system size dependence. Furthermore, predictions for the invariant mass spectra of dielectron emission are provided.
The production of light (anti-)(hyper-)nuclei in heavy-ion collisions at the LHC is considered in the framework of the Saha equation, making use of the analogy between the evolution of the early universe after the Big Bang and that of "Little Bangs" created in the lab. Assuming that disintegration and regeneration reactions involving light nuclei proceed in relative chemical equilibrium after the chemical freeze-out of hadrons, their abundances are determined through the famous cosmological Saha equation of primordial nucleosynthesis and show no exponential dependence on the temperature typical for the thermal model. A quantitative analysis, performed using the hadron resonance gas model in partial chemical equilibrium, shows agreement with experimental data of the ALICE collaboration on d, 3He, 3ΛH, and 4He yields for a very broad range of temperatures at T≲155 MeV. The presented picture is supported by the observed suppression of resonance yields in central Pb-Pb collisions at the LHC.
The new experiment PADME is located in the Beam Test Facility of the INFN Laboratori Nazionali di Frascati and its main goal its to search for a light boson A′ (usually called dark photon) associated to a broken U(1) gauge symmetry holding in a secluded sector and acting as a portal between the visible and the dark sector.
PADME has collected a first set of commissioning data in 2018/2019 which are used to establish its performance, to refine the reconstruction algorithms and to tune the simulation software by using standard model processes.
The main physics processes are positron-electron annihilation in two photons and the positron bremsstrahlung. The first process can be reconstructed from events with two back-to-back photons in time inside the main electromagnetic calorimeter acceptance, and the second process with a photon, inside the small-angle calorimeter, in time with a positron hitting the positron veto after bending in a dipole magnetic field. A crucial outcome of these studies is to establish the beam induced background not predicted by the experiment simulations for example due to the beam non-gaussian tails hitting the transport line or the target support structure.
The study of hadronic resonances by the ALICE experiment is of special importance in order to disentangle the hadronic final-state effects in relativistic heavy-ion collisions at the LHC. Short-lived hadronic resonances are sensitive probes of the dynamics and properties of the medium formed after hadronisation. Due to their short lifetimes, they decay when the system is still dense and the decay products scatter in the hadron gas. Possible interaction mechanisms inside the hadronic medium involve the competing processes of hadron re-scattering and re-generation, which can have a strong influence on the shapes of the $p_{\rm T}$ spectra and on the re-constructible total yields.
The ALICE experiment has measured the production of a rich set of hadronic resonances such as $\rho(770)^{0}$, $K^{\ast}(892)$, $\phi(1020)$, $\Sigma(1385)^{\pm}$, $\Lambda(1520)$ and $\Xi(1530)^{0}$, in pp, p-Pb and Pb-Pb collisions at various energies at the LHC. A comprehensive overview of the latest results will be presented. Transverse momentum spectra, mean transverse momenta and total yield production ratios to stable particles will be presented as a function of charged particle multiplicity/centrality and collision energies. Comparisons with the predictions from various statistical hadronisation models, Monte Carlo event generators like EPOS3 with UrQMD as an afterburner will also be discussed.
The light-cone definition of Parton Distribution Functions (PDFs) does not allow for a direct ab initio determination employing methods of Lattice QCD simulations that naturally take place in Euclidean spacetime. In this presentation we focus on pseudo-PDFs where the starting point is the equal time hadronic matrix element with the quark and anti-quark fields separated by a finite distance. We focus on Ioffe-time distributions, which are functions of the Ioffe-time ν, and can be understood as the Fourier transforms of parton distribution functions with respect to the momentum fraction variable x. We present lattice results for the case of the nucleon and the pion and we also perform a comparison with the pertinent phenomenological determinations.
Multi-messenger astronomy with high-energy neutrinos
Hadron polarizability measurements.
Status of the B-meson flavor anomalies
Scattering experiments have been one of the main sources of information on hadron-hadron interactions. They provide a large amount of data on nucleon-nucleon potentials but a limited amount for hyperon-nucleon and hyperon-hyperon pairs.
The understanding of interactions amongst baryon and anti-baryons as well rely on an even smaller set of data involving mostly nucleon-antinucleon sector.
Hypernuclei data, in the hyperon-nucleon sector, and exotic atoms, as for kaonic hydrogen or protonium, can provide constraints on the strong interaction but only at the production threshold.
The need for more data, in particular at low momenta, demands a new experimental observable sensitive to the underlying strong interaction. At the moment only the femtoscopy technique is able to fulfill both requirements.
Femtoscopy is a method to study correlations between particles with low rest-frame relative momentum $\mathrm{k}^*$, which can be related to the emission source and interaction potential.
Recently, ALICE femtoscopic measurements in pp and p-Pb collisions proved to be able to access the short-range strong interaction among hadron pairs that are otherwise not easily accessible with ordinary scattering experiments.
With High-Multiplicity events in pp collisions at 13 TeV, more precise measurements on several pairs interaction and on the emitting source have been performed and will be shown in this talk.
In particular, we will show results from the analysis of the p-p correlation function which allows us to build a consistent treatment of the emitting source for all hadron pairs based on $m_T$ scaling and by accounting for strongly decaying resonance contributions. The first measurements of the p-$\Sigma_0$ and p-$\Omega$ strong interaction will be presented along with a comparison to available theoretical models based on Lattice and effective Lagrangian calculations. Finally, results from baryon-antibaryon pairs (p-$\bar{p}$, p-$\bar{\Lambda}$ and $\Lambda$-$\bar{\Lambda} will be shown for the first time.
For 20 years the Pierre Auger Observatory is measuring ultra-high energy cosmic rays. Among the early discoveries was the confirmation of a strong suppression of the flux of cosmic rays at energies beyond 10EeV. If cosmic rays were mostly protons of extragalactic origin, as it was supposed, such a suppression is expected from the absorption of cosmic rays in the CMB. However, subsequent measurements of the mass of cosmic rays revealed the presence of heavy nuclei in the flux. While a flux purely composed of protons is ruled out, studies of the arrival directions have recently delivered strong evidence for the extragalactic origin and some evidence for a correlation with star-burst-galaxies. The picture that is emerging is thus of a complex and nuanced universe at the highest energies. But what if ... ?
What if the interpretation of the mass measurements is askew because we fail to account for a new aspect in the interactions of the cosmic rays with the atmosphere? After all the energy scale of ultra-high energy cosmic rays is an order of magnitude larger than the energies probed at the LHC. Indeed, measurements of the average muon content of air showers induced by ultra-high energy cosmic rays, a quantity that is closely linked to the hadronic activity in the shower, reveal a curious discrepancy when comparing to expectations from theory. Could this muon excess be the telltale sign of new physics? Does the picture of ultra-high energy cosmic rays have to be revised yet again?
In this presentation the measurements by the Pierre Auger Observatory that led to the current picture of ultra-high energy cosmic rays will be introduced. Particular focus is put on measurements of muons in air showers and how these fit in the current picture and why the scenario of new physics is disfavored.
Low-energy cosmic anti-deuterons are unique probe for search of exotic processes in the Universe such as Dark Matter annihilation, since the production rate of these ions through secondary processes in interstellar medium is very low. However, the lack of experimental data at low energies hampers precise predictions of the expected anti-deuteron fluxes near Earth, with both anti-deuteron nuclear inelastic cross-section with matter and anti-deuteron production cross-section being known very poorly by today.
In ultra-relativistic collisions of protons and lead ions at the CERN's Large Hadron Collider matter and anti-matter is produced in almost equal abundances. This allows us not only to study the production cross-sections of (anti-)deuterons with high precision, but also to quantify the absorption of produced (anti-)deuterons in the detector material. The latter can be investigated via comparison of raw reconstructed yields of particles and anti-particles in experimental data and in Monte Carlo simulations.
In this talk we present the first results on the anti-deuteron absorption cross-section in the ALICE detector material using p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The reconstructed anti-deuteron to deuteron ratio is compared to the results from detailed simulations of the ALICE detector based on different versions of the GEANT toolkit for particle propagation and interaction with matter. First experimental constraints on the anti-deuteron nuclear inelastic cross-section are extracted in the momentum range between 0.3 and 4.0 GeV/$c$. Finally, we discuss the perspectives for future measurements using high-statistics data from proton-proton collisions at $\sqrt{s}$ = 13 TeV.
The PUMA project (antiProton Unstable Matter Annihilation) aims at using low energy antiprotons to probe the tail of the radial density of short-lived nuclei. With PUMA, the ratio of proton and neutron annihilations after capture will be determined, giving access to a new observable to quantify the ratio of proton to neutron densities at the nuclear periphery. PUMA aims at transporting one billion low-energy antiprotons (produced at CERN/ELENA) to the CERN/ISOLDE facility where short-lived nuclei are produced. In the talk, an overview of the project and its current status will be given. In particular, the foreseen concept for extreme high vacuum for antiproton storage and the analysis method to determine the proton to neutron annihilation ratio will be detailed.
The momentum distribution in the final state of ion collisions is explained by the collective evolution of the initial energy density in a heavy-ion experiment. Due to the low statistic in a single event, this model is tested by studying many events. Consequently, the observation is convoluted by statistical fluctuation which contains information about the statistical properties of the initial state as well. After surprising observation of flow-like features in small systems, it has been turned out that, at least apparently, the collective picture is applicable for proton-proton and proton-ion collisions. In this talk, we first study the potential information encoded in statistical studies of flow fluctuations. Specifically, we introduce the generalized symmetric cumulants which probe the genuine multi-harmonic correlation. Regarding the flow-like observation in small systems, we study the applicability of hydrodynamics in a different range of system size by employing Gubser flow. After that, we introduce a simple and rather generic model for fluctuations in proton-proton collisions in order to explain the experimentally observed flow harmonics in small systems.
Based on:
[1] C. Mordasini, A. Bilandzic, D. Karakoç, S. F. Taghavi, "Higher order Symmetric Cumulants", [arXiv:1901.06968v2 [nucl-ex]]
[2] S. F. Taghavi, "Smallest QCD Droplet for Hydrodynamic Response and Multiparticle Correlations in pp Collisions", [arXiv:1907.12140v1 [nucl-th]]
The Belle II experiment at SuperKEKB, an asymmetric $e^+e^-$ collider, has a rich program of Standard Model and Beyond the Standard Model physics.
The collider, a next generation B factory, started operation in 2016 and successfully commissioned with first collisions in April 2018. In 2019 a first physics run with the full Belle II detector has taken place. Ultimately
SuperKEKB will reach a world-record luminosity of 8x10$^{35}$ cm$^{-2}$s$^{-1}$ and aims to record a database of 50 ab$^{-1}$.
In the area of tau physics, this will enable new and/or more precise measurement of Standard Model processes as well as Beyond the Standard Model searches.
Because of its well understood electroweak production and decay mechanisms and its high mass of above 1.7 GeV the tau lepton is an excellent probe for physics beyond the standard model, and provides clean samples for studying QCD at the 1 GeV energy level.
This contribution will give a compact overview over the tau physics programme at Belle II, with a particular emphasis on first results and decay modes with significant potential in the near future.
Neutron-rich matter in heaven and on Earth
Probing the EOS in Heavy ion Collisions
Astrophysics studies with stores exotic nuclei
"Selected results of the LHCb experiment on heavy ion collisions studied in the collider and fixed-target modes will be presented. The clear evidence of the impact of the production mechanism (prompt/delayed, p-p or p-Pb systems) on the transverse momentum and rapidity distributions for 𝐽/𝜓, 𝐷0 and ϒ(𝑛𝑠) species is demonstrated. The interpretation of the observations in frames of theoretical models is briefly discussed."
Recent Flavour results from LHCb
Reaching new precision frontiers in nuclear physics brings up new experimental challenges as well as the demand for more sophisticated theoretical calculations. Especially in parity-violation electron scattering experiments the contribution from higher order processes, such as two-photon exchange, is comparable in size with the observed asymmetry $A_{PV}$. Hence, a precise knowledge of this contribution is mandatory to determine the systematic uncertainties.
Beam-normal single-spin asymmetries $A_{n}$ (or so-called transverse asymmetries) are a direct probe of the imaginary part of the two-photon exchange amplitude in the elastic scattering of transversely polarized electrons from unpolarized nucleons. Up to now, there is significant disagreement between experiment and theory for $^{208}$Pb, which motivates more measurements to study the $Q^{2}$ and $Z$ dependence. During a successful campaign at the MAinz MIcrotron (MAMI), using the spectrometer setup of the A1 collaboration, the $Q^{2}$ dependence of $A_{n}$ for $^{12}$C was measured. The follow-up experiments on $^{28}$Si and $^{90}$Zr investigate the charge dependence of the transverse asymmetry at one $Q^{2}$ point, thus benchmarking the theoretical calculations in the heavier mass regime
The HADES spectrometer is located at the SIS18 accelerator at the GSI Helmholtzzentrum für Schwerionenforschung GmbH in Darmstadt. Recently an electromagnetic calorimeter (ECAL) detector was added to the set-up. The ECAL read-out system is based on the PaDiWa-AMPS Charge-to-Time-over-Threshold front-end board for the Trigger and Read-out Board (TRB) platform. The required discriminators, the high precision Time-to-Digital-Converters and the data acquisition functionality are implemented with the help of Field Programmable Gate Arrays. In this contribution the ECAL read-out system will be introduced and its performance will be shown. The possibility to use the TRB-platform for beam monitoring purposes will be addressed. Special emphasis will be put on new developments utilizing Ultra Fast Silicon Detectors for beam monitoring and T0 determination in HADES.
In heavy nuclei, the distribution of neutrons extends out further than the proton distribution forming a so-called “neutron skin”. An accurate experimental determination of the neutron skin thickness of heavy nuclei would provide a unique constraint on the symmetry energy of the nuclear Equation Of State which strongly depends on poorly constrained three-body forces. Photons have an advantage over other nuclear probes for this purpose since they can interact with the whole volume of the nucleus without any Coulomb scattering effects.
Coherent neutral pion photoproduction on nuclei (γ + A → π_0 + A, where A is a nucleus in its ground state) is an attractive approach to obtain information on the distribution of neutrons. The spin-zero nuclei are of special interest since in this case protons and neutrons contribute with the same amplitude to the coherent photoproduction in the incident photon energy range from threshold to 350 MeV. Therefore, the reaction is sensitive to the distribution of nucleons and the measured cross section is proportional to the nuclear mass form-factor [1]. Information on the neutron distribution can be extracted by comparing the diffraction pattern of the measured cross section with theoretical calculations. Recently, the skin thickness in 208Pb was measured in this way by the A2 collaboration at MAMI [2].
The method of coherent pion photoproduction provides an efficient tool to study the neutron skin however requires a reliable theoretical model. Because the cross section is strongly affected by final-state interactions of the pion on the way out of the nucleus, this effect has to be accounted for in the model calculations [2].
In this work, we develop a new coherent pion photoproduction reaction code in the framework of the distorted wave impulse approximation in the momentum space. To reliably account for the pion-nucleus final-state interaction we devise a second-order pion-nucleus optical potential which involves analysis of pion-nucleus elastic scattering as a solution of the Lippmann-Schwinger equation. The optical potential is constructed on the base of the individual pion-nucleon scattering amplitudes extracted from SAID [3] and the harmonic oscillator shell model is used to develop its second-order part. Finally, we estimate optimal energy-independent parameters of the optical potential by a global fit of pion-carbon total, reaction and differential elastic cross sections.
[1] D. Drechsel et al., Nucl. Phys. A 660, 423 (1999).
[2] C. M. Tarbert et al., Phys. Rev. Lett. 112, 242502 (2014).
[3] R. L. Workman et al., Phys. Rev. C 86, 035202 (2012).
We investigate the complex spectrum of the massive Dirac operator in 2+1-flavor QCD, at nonzero temperature and isospin chemical potential, using the extension of the Banks-Casher relation to the case of Complex Dirac eigenvalues (derived for the zero-temperature, high-density limits of QCD at nonzero isospin chemical potential), as a prescription to obtain information on the BCS gap from the 2d density of the complex Dirac eigenvalues.
Such study is motivated by the prediction, from perturbation theory, of a superfluid state of $u$ and $\bar{d}$ Cooper pairs (BCS phase) at asymptotically high isospin densities, plausibly connected via an analytical crossover to the a phase with Bose-Einstein condensation of charged pions at $\mu_I>=m_\pi/2$.
Further motivation comes from recent lattice observations (renormalized Polyakov loop measurements) that indicate a decrease of the deconfinement transition temperature as a function of \mu_I, suggesting that the deconfinement crossover smoothly penetrates into the pion condensation phase and thus favoring a scenario where the deconfinement transition connects continuously to the BEC-BCS crossover in the $(T,\mu_I)$ phase diagram.
The efficient production of cold antihydrogen atoms, at CERN's Antiproton Decelerator, has opened up the possibility to perform a direct measurement of the Earth's gravitational acceleration g on a purely antimatter system. Indeed, from the experimental point of view, very little is known about the gravitational interaction between matter and antimatter. In particular, the Weak Equivalence Principle (WEP), which is of paramount importance for the General Relativity, has not been directly probed with antimatter yet. This is the primary goal of the AEgIS experiment at CERN: to test the WEP on antimatter, by means of a direct measurement of g on antihydrogen atoms. The idea is to measure the vertical displacement of a pulsed antihydrogen beam passing through a moirè deflectometer, coupled to a position sensitive detector. The milestones achieved so far by AEgIS, on the way to perform this first direct measurement of g on antimatter, are presented.
In recent years, interest in charmonium spectroscopy has been renewed by
the unexpected discovery of multiple states that seemingly do not fit a conventional
charmonium (ccbar) assigment, the so-called XYZ states. Although there are strong
indications that these states are in fact exotic, there is no consensus on their
exact nature. Therefore, it is of high importance to gather as much information
as possible on the production and decays of the XYZ states.
The BESIII experiment at the Beijing Electron Positron Collider (BEPCII)
collected large dataset in the energy range 4.0 GeV- 4.60 GeV
dedicated to the study of these potentially exotic states in the charm
sector. Vector states, like the Y(4260), can be directly produced in e+e- annihilation
at BESIII; whereas other exotic candidates like the X(3872) and
the Zc(3900) are produced through processes of the type e+e- ->gamma X(3872)
and e+e- ->pi Zc(3900), respectively. Consequently, BESIII is in a unique
position to perform detailed studies on exotic hadrons in the charm
sector.
An overview of recent highlights of the BESIII program on XYZ states
will be given as well as an outlook on future perspectives with an upgraded
BEPCII allowing for higher center-of-mass energies.
Measuring Vorticity in the Quark Gluon Plasma
Recent Progress in Core-Collapse Supernovae Simulations
Deep Underground Neutrino Experiment
Search for Light Dark Matter at accelerators
We study the nuclear abundances produced by neutrino process during supernova (SN) explosion. In this presentation, we show the elements of $^{7}$Li, $^{11}$B, $^{92}$Nb, $^{98}$Tc, and $^{138}$La, which are mainly produced by neutrino reactions. To describe the neutrino-induced reaction rates, we consider the neutrino scattering with electron background and neutrinos themselves near the neutrino sphere. As a SN model, we use the SN1987A model for 16.2 $M_\odot$ progenitor with 6 $M_\odot$ He core. Also we consider the time dependent neutrino luminosities and averaged energies adopting 6 averaged SN simulation data. The changed neutrino spectra by this oscillation directly affect the $\nu$-nucleus reaction rate. As a result, the abundances of $^{92}$Nb, $^{98}$Tc, and $^{138}$La are decreased by factor of 1.5-2, while $^{7}$Li and $^{11}$B abundances depends on neutrino mass hierarchy.
We investigate the electron screening effect on the stellar nucleosynthesis. The dense electron gases in the stellar environments screen the Coulomb interaction between reacting nuclei. In particular, the role of screening effects becomes important in the massive star since it consists of dense ions. In addition, most stellar objects have a magnetic field, which affects the electric screening potential for nuclear reactions. In this presentation, by using the Poisson-Boltzmann equation with the magnetic field, we show nuclear abundances synthesized in the massive star. We also discuss the possibility whether the distribution of ions in the screening effect can be changed by the kinetic theory.
The Belle II experiment at the SuperKEKB energy-asymmetric $e^+ e^-$ collider is a substantial upgrade of the B factory facility at the Japanese KEK laboratory.
Exploiting the improved collider, Belle II will play an important role in the Lepton Flavour Violation (LFV) field by collecting a huge amount of statistics (50 ab$^{-1}$ expected by 2028) which allows to probe new physics scenario with best precision. Several LFV measurement can be performed by investigating $\tau$ physics and Belle II, thanks to SuperKEKB, is going to contribute by providing a large $\tau$ sample with ``background free'' environment. This kind of analysis are very promising, in fact also many LHC groups are trying to get new results in this direction.\
This talk will review the state of the LFV searches at Belle II and it will focus on the analysis strategy of the decay $\tau \rightarrow \mu \mu \mu$ where a preforming muon identification algorithm is crucial.
Due to their large masses, heavy quarks are produced in the
early stages of the relativistic heavy-ion collisions via initial hard
scatterings. Therefore, they are considered as effective probes of the
hot and dense QCD medium formed in such collisions since they
witness its full evolution. In pp collisions, the measurement of heavy-
flavour hadron production cross-sections can be used to test our
understanding of the Quantum ChromoDynamics (QCD) in the
perturbative regime. In addition, pp collisions provide a crucial
reference for the corresponding measurements in larger systems. In
p-Pb and Pb-Pb collisions, the measurement of the nuclear
modification factor ($R_{\rm AA}$) of electrons from beauty hadron decays
shed light on the mass dependence of energy loss of quarks inside
the cold and hot nuclear matter by comparing the ($R_{\rm AA}$) of charm
hadrons with the one of beauty hadrons and pions. Along with this,
more differential measurements such as their production as a
function of the charge-particle multiplicity provide insight into the
role of Multiple Parton Interactions (MPI) and the interplay between
the hard and soft production mechanisms of the particles.
In this contribution, the results from ALICE at the LHC are
reported on the different measurements of leptons (electrons and
muons) from heavy-flavour hadron decays in pp, p-Pb and Pb-Pb
collisions at different center of mass energies. The results include the
differential production cross section, nuclear modification factors and
multiplicity dependence at mid rapidity. Comparisons of the results
with model calculations including the interaction of heavy quarks
with the QGP medium, as well as implementing mass-dependent
energy loss, will be shown.