Search

In recent years, interest in charmonium spectroscopy has been renewed by the unexpected discovery of multiple states that seemingly do not fit a conventional C C ¯ assigment. The BESIII experiment located at the BEPCII e+e− collider is at the forefront of investigations into these so-called XYZ states. With roughly 12 fb−1 of e+e− annihilation data above s = 3.8 GeV , BESIII both has direct access to exotic states with JPC = 1−− (Y-states) and can study X- and Z-states through radiative or mesonic transitions. Within the presentation, recent contributions of the BESIII experiment to the ongoing studies of XYZ states were highlighted and an outlook into future perspectives with BESIII was given. [ABSTRACT FROM AUTHOR]

Belle II at the electron-positron collider SuperKEKB is the successor to the Belle experiment. Its design luminosity is 8 · 1035/(cm2s), 40 times the record achieved at KEKB/Belle, at the same center of mass energy in the bottomonium region. Over the next years it is expected to accumulate an integrated luminosity of 50 ab−1, collecting by far the largest sample of B-mesons at electron-positron colliders, together with large numbers of bottomonium and lighter particles. After a commissioning run in 2018 the detector started routine data taking in March 2019. In these proceedings the current status of the detector, current and future running conditions and further prospects for the future are discussed. [ABSTRACT FROM AUTHOR]

The large data sample accumulated by the Belle experiment at KEKB asymmetric energy e+e− collider provides opportunities to study charmonia (bottomonia) and charmonium-like (bottomonium-like) exotic particles. In this review, we report recent results on these topics from Belle, including searches for B → hcK, B → Y (4260)K, B → X (3872/3915)(→χc1π0)K, B0 → X (3872)γ, e+e− → γχcJ and a new measurement of the e+e− → ϒ(nS)π+π−(n = 1, 2, 3) cross sections at energies from 10.52 to 11.02 GeV. [ABSTRACT FROM AUTHOR]

The possible importance of threshold effects in heavy quarkonium spectroscopy is discussed. The starting point is the calculation of the spectrum of heavy quarkonium-like states with self-energy/threshold corrections. Two different approaches are compared: I) The Unquenched Quark Model (UQM); II) A novel coupled-channel model, based on the UQM formalism. The latter provides a possible solution to the long-standing problem of convergence in UQM calculations; it also makes it possible to distinguish between states which are almost pure quarkonia and exotic states, characterized by non-negligible threshold (or continuum) components in their wave functions. The UQM-based coupled-channel model is used to study the χc(2P) and χb(3P) multiplets: χc(2P)'s are described as charmonium-like states with non-negligible molecular-type components in their wave functions, χb(3P)'s as almost pure bottomonia. Other possible applications of the UQM and the UQM-based coupled-channel model formalisms to the calculation of other observables, like the strong decay amplitudes, are also discussed. [ABSTRACT FROM AUTHOR]

Understanding the nature of the baryon spectrum will provide useful insight in the non-perturbative regime of quantum chromodynamics. Significant progress has been made in the N* regime, but little is known about doubly-strange hyperons. Most knowledge of the Cascade baryons stems from kaon-nucleon experiments from the 1960s and 1970s or the more recent CLAS experiment at Jefferson Lab. This research studies doubly-strange baryons via photoproduction using the GlueX experiment at Jefferson Lab. The Cascade octet ground state Ξ− can be studied in exclusive t-channel production in the reaction γp → KY* → K+(Ξ−K+) with the subsequent decay of the Ξ− into Λπ−. The production model suggests the intermediate hyperon Y* is broad and possibly consists of overlapping states. With GlueX Phase-I data taking concluded, preliminary total cross section results of the Cascade ground state Ξ−(1320) are presented. An exploration into the reaction Ξ−* → K−Λ is also shown. [ABSTRACT FROM AUTHOR]

The Ξ excited states are not well understood because of less experimental study. In this presentation, we report on the studies of Ξ(1620)0 and Ξ(1690)0 via the Ξ c + → Ξ − π + π + decays by using a data sample collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. We observe the Ξ(1620)0 in the Ξπ decay mode and measure its mass and width. We find an evidence of the Ξ(1690)0 in the Ξπ decay mode. [ABSTRACT FROM AUTHOR]

The Karlsruhe Tritium Neutrino (KATRIN) experiment aims to make a precision measurement of the effective neutrino mass by leveraging the kinematics of tritium beta decay, with a sensitivity of 0.2eV (90% C.L.). Recent run campaigns, both in standard mode (using molecular Tritium) and calibration mode (using 83mKr) operation, have provided a wealth of data. The models which we use to fit these data include information about the decay physics, and is convolved with a response function, which encodes details of the experimental setup into the model. In order to achieve the design sensitivity levels, our understanding of systematics must be under control. To this end, we explore KATRIN systematics and their effects on certain model fit parameters. A summary of preliminary results will be given here, as well as an outlook to both the immediate and extended future. [ABSTRACT FROM AUTHOR]

Deeply Virtual Compton Scattering (DVCS) is the simplest exclusive process to access Generalized Parton Distributions (GPDs). GPDs encode the correlation between the spatial distribution of partons inside the nucleon and their momentum. An upcoming DVCS experiment in Hall C at Jefferson Lab (Virginia, U.S.A.) will provide the highest precision data in a vast Q2-xB region accessible by an 11 GeV electron beam. It will further test the leading-twist dominance of the observables and get more precise data in the lower xB region needed for the full mapping of GPDs. A Neutral Particle Spectrometer (NPS) is being developed for this experiment. It consists of an electromagnetic calorimeter made of 1080 PbWO4 crystals and a sweeping magnet. This document will present the status of the detector R&D and construction, as well as simulation results of its performance. [ABSTRACT FROM AUTHOR]

The unquenched quark model for meson is explored in the present work. The quark-pair creation operator, which mix the two-quark and four-quark components, from 3P0 model is modified by considering effects of the created quark pair's energy and the separation between the created quark pair and the valence quark pair. All the wave functions needed are obtained by solving the corresponding Schrödinger equation with the help of the Gaussian expansion method. The results show that the unquenched quark model is convergent and some exotic states, for example X (3872) can be described well in the unquenched quark model. [ABSTRACT FROM AUTHOR]

The BESIII experiment at the Beijing Electron Positron Collider (BEPCII) has collected the world's largest data sample of J/ψ events (10 billion), which offers a unique opportunity to study hadron spectroscopy and search for light exotic states. In 2003, BESIII reported the first observation of a p p ¯ mass threshold enhancement X (p p ¯) in J/ψ → γp p ¯. In addition, a structure was observed in J/ψ → γη′π+π− and J/ψ → γKsKsη in 2005 and 2015 called X(1835). Both were determined to have spin-parity JP = 0−. While the masses of the X(p p ¯) and X(1835) are in agreement with each other, their widths are significantly different. Additionally, detailed studies of J/ψ → γη′π+π− show a significant abrupt change in slope of the X(1835) η′π+π− line shape at the p p ¯ mass threshold. An overview of recent developments of the mentioned observations as well as approaches to understand the line shape was given during the conference. [ABSTRACT FROM AUTHOR]

The large data sample accumulated by the Belle experiment at KEKB asymmetric energy e+e− collider provides opportunities to study hyperons and charmed baryons. We report recent measurements on these topics from Belle, including observations of new excited Ω− and Ξc, and first measurements of absolute branching fractions for ground states, Ξ c 0 and Ξ c + . [ABSTRACT FROM AUTHOR]

We report current status of the LEPS2 solenoid spectrometer for photoproduction experiments at SPring-8. A large solenoid LEPS2 spectrometer consists of a time projection chamber (TPC), drift chambers, resistive plate chambers and Pb/scintillator sampling calorimeters for photoproduction of hadrons in the energy range from 1.4 to 2.9 GeV. We have developed a new, network-distributed data acquisition system based on DAQ-middleware framework. The DAQ middleware components include gatherers collecting data from detector sub-systems, mergers integrating data from gatherers, and an event builder in the data acquisition software. Over ten thousand pad signals from the TPC are digitized with 40 MS 12-bit flash ADCs and then sent to a TPC gatherer through Space-Wire protocol. During the beam commissioning, Compton-backscattered photon beam was incident on a CH2 target in the energy region from 1.4 GeV to 2.4 GeV. We report on the performance test results of the new DAQ system with beam commissioning of the LEPS2 spectrometer as well. [ABSTRACT FROM AUTHOR]

Electromagnetic baryon form factors are excellent tools to investigate the hadronic structure. Many unexpected features have recently been found by BESIII and other experiments concerning e + e − → N N ¯ as well as e + e − → B B ¯ close to their thresholds, such as oscillations in the proton time-like effective form factor as a function of the energy and steep steps in the cross section at threshold followed by a plateau in e + e − → p p ¯ , and similar behaviour in e + e − → Λ c Λ ¯ c or in other e + e − → B B ¯ cross sections. Recent unxpected results for e + e − → Λ Λ ¯ are reported as well. [ABSTRACT FROM AUTHOR]

The formalism devoted to the production of two pseudoscalar mesons with a linearly polarized photon beam has been detailed and illustrated in arXiv:1906.04841. This document reports the necessary formulas, without proof, to perform an analysis of the angular distribution of two mesons photoproduction. The relations to extract moments of the angular distribution are provided, as well as the relations between the moments and the partial waves for a system involving S-, P- and D-waves. The expressions of the integrated beam asymmetry and the beam asymmetry along the y axis in term of moments are mentioned. [ABSTRACT FROM AUTHOR]

The paper is devoted to four-body Faddeev-type AGS equations, written down for the K ¯ NNN system, which is a system consisting of an antikaon and three nucleons. The aim is to find possible quasi-bound state in the system and calculate its properties. [ABSTRACT FROM AUTHOR]

Investigating few-body systems with identical particles in a hyperspherical basis yields the problem of obtaining symmetrized hyperspherical functions from functions with arbitrary quantum numbers. This article solves the problem of hyperspherical basis symmetrization for four-, five-, and six- body systems using Parentage Scheme of Symmetrization. Parentage coefficients and transformation coefficients corresponding to the [4], [31], [22], [211], representations of S4 groups with specific quantum numbers are obtained, and relationship between parentage coefficients and transformation coefficients between different sets of Jacobi coordinates for six-body systems are derived. Young operators, acting on N = 4, 5, 6 body hyperspherical functions symmetrized with respect to (N-1) particles, are derived. The symmetrized N = 4, 5, 6 body hyperspherical functions are obtained with different values of quantum numbers. The connection between the transformation coefficients for the identical particle systems and the parentage coefficients is demonstrated and the corresponding formulas are introduced. [ABSTRACT FROM AUTHOR]

We present a new method to determine the electromagnetic form factors by combining ingredients from dispersion theory with the standard chiral calculations. We show that with this approach one can determine the electromagnetic form factors of the nucleon up to energies of Q2 ≤ 2 GeV2. The results can be applied to determine que proton charge radius from the current low Q2 data (Q2 ≤ 0.5 GeV2) without the need of any extrapolation to Q2 = 0. The extracted value, r E p = 0.844 (7) fm , is in good agreement with the muonic hydrogen spectroscopy result. [ABSTRACT FROM AUTHOR]

The E12-09007 experiment in CLAS12 of Hall B at Jefferson lab proposed to measure multiplicities and longitudinal double spin asymmetries for pions (π+, π, π0) and kaons (K+, K, K0s) in Semi-Inclusive Deep Inelastic Scattering (SIDIS) from both hydrogen and deuterium. The data will be used to measure the x-dependence of the strange parton distribution function (PDF) and will help constrain the global fits used to obtain the fragmentation functions (FF). In addition this data will allow the extraction of the individual contributions of quarks and anti-quarks to the nucleon spin. The experiment is scheduled in two parts: the first involves unpolarized beam and targets for multiplicity and strange PDF measurements, the second uses both polarized beam and targets for the spin flavor decomposition. The measurements will cover the x-range from 0.05 to 0.7. Part of the unpolarized measurements was achieved in winter and data taking will continue at the end of this year. The polarized part of the experiment will run in a few years. The experiment requires the use of a Ring Imaging Cherenkov (RICH) detector for a successful charged kaon identification in the 3 to 8 GeV/c momentum range. One full RICH detector was recently built and is functional; a second one is under construction. [ABSTRACT FROM AUTHOR]

Polarizabilities are fundamental properties related to the internal structure and dynamics of the nucleon. They play a crucial role not only in our understanding of the nucleon, but also in other areas such as atomic physics. The A2@MAMI Collaboration has undertaken a comprehensive program of real Compton scattering experiments in order to accurately determine these parameters at the Mainz Microtron (MAMI), using the Crystal Ball/TAPS setup. A new high quality data-set has been collected both on the differential cross section and on the beam asymmetry Σ3 below the pion production threshold using a polarized photon beam and an unpolarized liquid hydrogen target. This measurement will allow an extraction of the proton scalar polarizabilities αE1 and βM1 with a significant improvement to the large uncertainties of the present values. Moreover, the use of linearly and circularly polarized photon beams in conjunction with polarized targets will also allow an extraction of the different proton spin polarizabilities, which at the moment have only been determined in various linear combinations. To study these, the asymmetries Σ2x, Σ2z and Σ3 were measured above the pion production threshold. [ABSTRACT FROM AUTHOR]

The study of anisotropic flow provides strong constrains to the evolution of the medium produced in heavy ion collisions and its event-by-event geometry fluctuations. The strength and predominance of these observables have long been related to collective behaviour in the formed medium. Recent results in small systems both at the Relativistic Heavy Ion Collider RHIC and the Large Hadron Collider LHC provide strong arguments for the formation of such medium at those scales. PHENIX has measured the v2 and v3 anisotropic flow coefficients for p+Au, d+Au, and 3He+Au collisions at 200 GeV as well as d+Au at various lower energies. We find that the flow coefficients match the ordering from the initial geometry. Moreover we show that the flow coefficients in all systems are very well described by the predictions from hydrodynamic models [1]. [ABSTRACT FROM AUTHOR]

The GlueX facility, featuring a linearly polarized 9 GeV real photon beam delivered to a large-acceptance detector system, has recently completed its first phase of running, and analysis efforts of this dataset are well underway. It has been suggested that at GlueX energies, quark systems beyond the three quark and quark-antiquark systems of baryons and mesons, such as hybrid mesons, tetraquarks and glueballs, should exist, and studies of these systems could shed new light on how quarks combine under the strong force, particularly the role played by gluons. GlueX data encompasses final states at energies where photoproduction of light scalar mesons, such as a0(980) and f0(980), can provide discriminatory evidence between various models, manifested in experimental observables such as the cross section and beam asymmetry, however many of these analyses comprise multi-particle final states, which can arise from numerous intermediate resonances formed via different production mechanisms. The work presented showcases efforts to measure the beam asymmetry of the reaction γp → pηπ, with a particular interest in future studies of the a0(980) meson, and discusses the application of longitudinal phase space plots, originally introduced by van Hove fifty years ago, as a means of optimizing event selection. This technique has found traction in several multi-particle final state analyses in GlueX, and provides an effective additional means of separately visualising meson and baryon production events with the same final state. [ABSTRACT FROM AUTHOR]

Zc(4430) discovered in B ¯ 0 → ψ (2 S) K − π + , Zc(4200) found in B ¯ 0 → J / ψ K − π + , and Z1(4050) and Z2(4250) observed in B ¯ 0 → χ c 1 K − π + are candidates of charged charmonium-like states. All surviving theoretical models interpreted these candidates as four-quark states, until we recently identified a compelling alternative. We discuss that kinematical singularities in triangle loop diagrams induce a resonance-like behavior that can consistently explain the properties (such as spin-parity, mass, width, and Argand plot) of Zc(4430), Zc(4200), Z1(4050) and Z2(4250) from experiments. In terms of the triangle singularities, we can also naturally understand interesting experimental findings such as the appearance (absence) of Zc(4200)(Zc(4430))-like contribution in Λ b 0 → J / ψ p π − , and the highly asymmetric shape of the spectrum bump for Z1(4050); the other theoretical models have not successfully addressed these points. Although Pakhlov et al. proposed another triangle diagram to generate a Zc(4430)-like bump, we argue that this scenario is very unlikely. [ABSTRACT FROM AUTHOR]

The GlueX experiment at Jefferson Lab aims to study the light meson spectrum with an emphasis on the search for hybrid mesons. To this end, a linearly-polarized 9 GeV photon beam impinges on a hydrogen target contained within a detector with near-complete neutral- and charged-particle coverage. In 2018, the experiment completed its first phase of data taking in its design configuration and the quantity of analyzed data already exceed that of previous experiments for polarized photoproduction in this energy regime by orders of magnitude. Polarization observables such as spin-density matrix elements provide valuable input for the theoretical description of the production mechanism, which will be essential for the interpretation of possible exotic-meson signals. We present results for the photoproduction of vector mesons, focusing on the unprecedented statistical precision of the spin-density matrix elements for the ρ(770) meson. [ABSTRACT FROM AUTHOR]

The study of the spectrum and structure of excited nucleon states employing the electroproduction of exclusive reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. The CLAS detector in Hall B has provided the dominant part of the available world data on most relevant meson electroproduction channels off the nucleon in the resonance region for Q2 up to 5 GeV2. Analyses of CLAS data for the exclusive channels πN, ηN, and π+π−p on a proton target have provided the only results available on the Q2 evolution of the electro-excitation amplitudes for the transitions from the initial photon-proton to the final N* states in the mass range up to W =1.8 GeV. These electrocouplings allow for exploration of the internal structure of the produced excited nucleon states. This work has made it clear that consistent results from independent analyses of several exclusive channels with different resonance hadronic decay parameters and non-resonant backgrounds but the same N* electro-excitation amplitudes, is essential to have confidence in the extracted results. Starting in early 2018, a program to study the spectrum and structure of N* states in various exclusive electroproduction channels using the new CLAS12 spectrometer commenced. These studies will probe the structure of N* states in the mass range up to W =3 GeV and for Q2 as low as 0.05 GeV2 and as high as 10-12 GeV2, thus providing a means to access N* structure information spanning a broad range of distance scales. Quasi-real photoproduction studies are also planned to search for additional N* states, the so-called hybrid baryons, for which the glue serves as an active structural component. In this talk the N* programs from both CLAS and CLAS12 will be reviewed. [ABSTRACT FROM AUTHOR]

The NA62 experiment at CERN Super Proton Synchrotron was designed to measure BR(K+ → π+ν v ¯) with an in-fight technique, never used before for this measurement. This decay is characterised by a very precise prediction in the Standard Model. Its branching ratio, which is expected to be less than 10−10, is one of the best candidates to indicate indirect effects of new physics beyond SM at the highest mass scales. NA62 result on K+ → π+ν v ¯ from the full 2016 data set is described. Also a search for an invisible dark photon A′ has been performed, exploiting the efficient photon-veto capability and high resolution tracking of the NA62. The signal stems from the chain K+ → π+π0 followed by π0 → A′γ. No significant statistical excess has been identified. Upper limits on the dark photon coupling to the ordinary photon as a function of the dark photon mass have been set, improving on the previous limits over the mass range 60 - 110 MeV/c2. [ABSTRACT FROM AUTHOR]

Recent developments in studying the φ meson in nuclear matter are summarized and reviewed from a theoretical point of view. Special emphasis is laid on the most recent results dealing with the momentum dependence of the φ meson properties in medium and a first attempt at simulating the pA reactions employed in experimental studies of the φ meson in nuclear matter, making use of a transport model approach. [ABSTRACT FROM AUTHOR]

Recent progress in deciphering few-body light hypernuclear systems, reported at MENU-2019, Pittsburgh PA, June 2019, is summarized on the following issues: (i) resolving the Λ 5 He overbinding problem in single-Λ hypernuclei; (ii) arguing that the onset of binding double-Λ hypernuclei occurs at A = 5; and (iii) revisiting the loosely bound Λ 3 H lifetime evaluation, given recent claims from relativistic heavy ion experiments that τ( Λ 3 H) is shorter than the free-Λ lifetime τΛ by as much as 30-40%. [ABSTRACT FROM AUTHOR]

The observation of a non zero electric dipole moment of a fundamental particle would represent a clear sign of New Physics beyond the Standard Model. An experimental program is presently pursued by the JEDI Collaboration at the COSY storage ring of the Forschungszentrum Jülich (Germany) to provide the first ever measurement of the electric dipole moment of the deuteron. The gained experienced and developed technologies result important in perspective of the design and realization of a future dedicated storage ring. [ABSTRACT FROM AUTHOR]

Exotic quarkonia are candidates to new types of hadrons including four quarks or gluonic degrees of freedom as constituents, the latter being a unique feature of QCD. We review recent developments in nonrelativistic EFTs to describe exotic quarkonia and in particular recent results on the spectrum of heavy hybrids including spin-dependent contributions up to 1 / m Q 2 -terms in the heavy-quark-mass expansion. We determine the nonperturbative contributions to the matching coefficients of the EFT by fitting our results to lattice-QCD determinations of the charmonium hybrid spectrum and extrapolate the results to the bottomonium hybrid sector where lattice-QCD determinations are still challenging. We also report on a recent new approach to quarkonium hadronic transitions that does not use the twist expansion and uses the hybrid spectrum as the intermediate octet states. [ABSTRACT FROM AUTHOR]

Lattice QCD calculations of resonant meson-meson scattering amplitudes have improved significantly due to algorithmic and computational advances. However, progress in meson-nucleon scattering has been slower due to difficulties in computing the necessary correlation functions, the exponential signal-to-noise problem, and the finite-volume treatment of scattering with fermions. Nonetheless, first benchmark calculations have now been performed. The status of lattice QCD calculations of meson-nucleon scattering amplitudes is reviewed together with comments on future prospects. [ABSTRACT FROM AUTHOR]

KLOE-2 has recorded 5.5 fb−1 of e+e− collisions at 1.019 GeV. A status report of the experiment plans and current analyses is given, including recent results in the KS sector that at the φ-factory is uniquely tagged by KL identification. Our attempt to exploit the lepton-tagging technique to identify virtual γγ processes in the high-luminosity environment of the φ-factory, the progress on the searches in the dark sector and in the analysis of the η → π0γγ decays are presented. [ABSTRACT FROM AUTHOR]

One of the most striking phenomenon of quantum chromodynamics (QCD) is the formation of the nucleon out of massless gluons and almost massless quarks. This system of confined quarks and gluons serves as the basic constituent of ordinary baryonic matter and exhibits the characteristic spectra of excited states, which are sensitive to the details of quark confinement. Complementary to nucleon structure studies in deep inelastic scattering experiments, nucleon excitations provide the unique opportunity to explore the many aspects of non-perturbative QCD. The last few years have seen significant progress toward the mapping of the nucleon spectrum. The rapidly growing database of high-quality experimental results on exclusive meson photo- and elec- troproduction on the nucleon from experimental facilities around the world now allows the hadron spectroscopy community to determine the scattering amplitudes of the underlying reactions more accurately and to identify nucleon resonance contributions with minimal model dependence. At Jefferson Laboratory (JLab), the excited baryon program now continues in the 12-GeV era with the successful data-taking of the GlueX experiment. Part of the GlueX scientific program is to search for and study the poorly-known multi-strange baryons which will provide an important missing link between the light- and the heavy-flavor baryons. [ABSTRACT FROM AUTHOR]

I overview our recent activity with the Argonne-Osaka dynamical coupled-channels (DCC) approach that provides a unified description of various electroweak meson productions on single nucleon and nucleus. First I discuss the DCC model of a single nucleon. The DCC model has been developed through a comprehensive analysis of πN, γN → πN, ηN, KΛ, KΣ reaction data. The model has been further extended to finite Q2 region by analyzing pion electroproduction data, and to neutrino-induced reactions using the PCAC relation. Next I discuss applications of the DCC model to electroweak meson productions on the deuteron. We consider impulse mechanism supplemented by final state interactions (FSI) due to NN and meson-nucleon rescatterings. Using this model, I discuss FSI corrections needed to extract γ-neutron reaction observables from γd → πNN, and a novel method to extract ηN scattering length from γd → ηpn. I also discuss FSI corrections on the existing neutrino-nucleon pion production data that had been extracted from neutrino-deuteron data. [ABSTRACT FROM AUTHOR]

The search for hybrid mesons and the detailed study of their spectrum is the primary goal of the GlueX Experiment in Hall D at Jefferson Lab. The identification and study of hybrid mesons promises to provide unique insight into gluonic degrees of freedom in QCD and the nature of confinement. The experiment combines an intense photon beam with linear polarization peaking around 9 GeV incident on a liquid hydrogen target with a nearly hermetic spectrometer, enabling the comprehensive study of charged and neutral particle final states. The first phase of the experiment has recently concluded, yielding a photoproduction data set of unprecedented size and quality. We report on the status of the analysis of this data, including measurements of polarization observables, progress in spectroscopic measurements of light mesons, and the measurement of the photoproduction of J/ψ near threshold, which is providing critical insight into the nature of the LHCb closed-charm pentaquark candidates. [ABSTRACT FROM AUTHOR]

We present measurements of the photon beam asymmetry Σ for the reaction γp → K+Σ0(1193) using the GlueX experiment in Jefferson Lab's Hall D. Data were collected using a linearly polarized photon beam with energy range 8.2-8.8 GeV incident on a liquid hydrogen target. Asymmetries are measured as functions of Mandelstam variables −t and −u. These are the first fully exclusive measurements of the photon beam asymmetry Σ in this reaction at high energies with detection of all final state particles. In the t-channel, results show that the reaction is dominated by the natural-parity exchange of presumably the K*(892) meson, as predicted by theoretical models. Results obtained for the u-channel are consistent with an intermediate baryon exchange mechanism predicted by theoretical models. [ABSTRACT FROM AUTHOR]

The "Physics Beyond Colliders (PBC)" study explores fundamental physics opportunities at the CERN accelerator complex complementary to collider experiments. Three new collaborations aim to exploit the M2 beamline in the North Area with existing high-intensity muon and hadron beams, but also aspire to go beyond the current M2 capabilities with a RF-separated, high-intensity hadron beam, under study. The AMBER/COMPASS++ collaboration proposes an ambitious program with a measurement of the proton radius with muon beams, as well as QCD-related studies from pion PDFs / Drell-Yan to cross section measurements for dark sector searches. Assuming feasibility of the RF-separated beam, the spectrum of strange mesons would enter a high precision era while kaon PDFs as well as nucleon TMDs would be accessible via Drell-Yan reactions. The NA64µ collaboration proposes to search for dark sector mediators such as a dark scalar A′ or a hypothetical Zµ using the M2 muon beam and complementing their on-going A′ searches with electron beams. The MuonE collaboration intends to assess the hadronic component of the vacuum polarization via elastic µ − e scattering, the dominant uncertainty in the determination of gµ − 2. An overview of the three new experimental programs will be presented together with implications for the M2 beamline and the experimental area EHN2, based on the studies of the PBC "Conventional Beams" Working Group. [ABSTRACT FROM AUTHOR]