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At least 1,369 records · Page 76

Open Heavy Flavor and Quarkonia Results at RHIC

RHIC experiments carry out a comprehensive physics program which studies open heavy flavor and quarkonium production in relativistic heavy-ion collisions. The discovery at RHIC of large high-pT suppression and flow of electrons from heavy quarks flavors have altered our view of the hot and dense matter formed in central Au + Au collisions at √S NN = 200 GeV. These results suggest a large energy loss and flow of heavy quarks in the hot, dense matter. In recent years, the RHIC experiments upgraded the detectors; (1) PHENIX Collaboration installed silicon vertex tracker (VTX) at mid-rapidity region and forward silicon vertex tracker (FVTX) at the forward rapidity region, and (2) STAR Collaboration installed the heavy flavor tracker (HFT) and the muon telescope detector (MTD) both at the mid-rapidity region. With these new upgrades, both experiments have collected large data samples. These new detectors enhance the capability of heavy flavor measurements via precision tracking. The PHENIX experiments established measurements of ψ(1S) and ψ(2S) production as a function of system size, p + p, p + Al, p + Au, and 3He + Au collisions at √S NN = 200 GeV. In p/ 3 He + A collisions at forward rapidity, we observe no difference in the ψ(2S)/ψ(1S) ratio relative to p + p collisions. At backward rapidity, where the comoving particle density is higher, we find that the ψ(2S) is preferentially suppressed by a factor of two. STAR Collaboration presents the first J/ψ and Υ measurements in the di-muon decay channel in Au + Au collisions at GeV at mid-rapidity at RHIC. Here, we observe clear J/ψ RAA suppression and qualitatively well described by transport models simultaneously accounting for dissociation and regeneration processes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Flavor tagged time-dependent angular analysis of the B s 0 → J / ψ ϕ decay and extraction of Δ Γ s and the weak phase ϕ s in ATLAS

A measurement of the B$ ^0_s $ →J/ψφ decay parameters, updated to include flavor tagging is reported using 4.9 fb -1 of integrated luminosity collected by the ATLAS detector from $ \sqrt{s} $=7 TeV pp collisions recorded in 2011 at the LHC. The values measured for the physical parameters are ϕ s =0.12±0.25(stat)±0.05(syst)rad ΔΓ s =0.053±0.021(stat)±0.010(syst)ps -1 Γ s =0.677±0.007(stat)±0.004(syst)ps -1 |A (0)| 2 =0.220±0.008(stat)±0.009(syst) |A0(0)| 2 =0.529±0.006(stat)±0.012(syst) δ ⊥ =3.89±0.47(stat)±0.11(syst)rad where the parameter ΔΓ s is constrained to be positive. The S-wave contribution was measured and found to be compatible with zero. Results for ϕ s and ΔΓ s are also presented as 68% and 95% likelihood contours, which show agreement with the Standard Model expectations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Sensitivity of D meson azimuthal anisotropies to system size and nuclear structure

Recent experimental data at the Large Hadron Collider (LHC) confirmed that the soft sector azimuthal anisotropies in central XeXe collisions are sensitive to deformations in the wave function of the Xenon nucleus. Additionally, the CMS experiment found that D meson flow is slightly suppressed compared to other particle species when considering quark number scaling in small systems of pPb compared to PbPb. In this talk we used the D and B Mesons Modular (DAB-MOD) code coupled to Trento+v-USPhydro to calculate the R AA and v n ’s of D mesons using different energy loss models and Langevin techniques. Comparing D mesons R AA and v n in PbPb to XeXe collisions it is found that in central collisions D meson azimuthal anisotropies are sensitive to details in the nuclear structure wave function of Xenon. Additionally, we find that in mid-central collisions the smaller system size of XeXe suppresses D meson flow.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Neutron Valence Structure from Nuclear Deep Inelastic Scattering

Mechanisms of spin-flavor SU(6) symmetry breaking in Quantum Chromodynamics (QCD) are studied via an extraction of the free neutron structure function from a global analysis of deep inelastic scattering (DIS) data on the proton and on nuclei from $A = 2$ (deuterium) to 208 (lead). Modification of the structure function of nucleons bound in atomic nuclei (known as the EMC effect) are consistently accounted for within the framework of a universal modification of nucleons in short-range correlated (SRC) pairs. Our extracted neutron-to-proton structure function ratio $F_2^n/F_2^p$ becomes constant for $x_B \ge 0.6$, equalling $0.47 \pm 0.04$ as $x_B \rightarrow 1$, in agreement with theoretical predictions of perturbative QCD and the Dyson Schwinger equation, and in disagreement with predictions of the Scalar Diquark dominance model. Finally, we also predict $F_2^{^3\mathrm{He}}/F_2^{^3\mathrm{H}}$, recently measured, yet unpublished, by the MARATHON collaboration, the nuclear correction function that is needed to extract $F_2^n/F_2^p$ from $F_2^{^3\mathrm{He}}/F_2^{^3\mathrm{H}}$, and the theoretical uncertainty associated with this extraction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Beam-Based Target Alignment for Mu2e

The Mu2e Experiment is a precision experiment at Fermi National Accelerator Laboratory, searching for charged lepton flavor violation (CLFV) in the conversion of a muon to an electron in the presence of an atomic nucleus. In order to achieve the expected single-event sensitivity of $3\times 10^{-17}$ , Mu2e will require an intense muon beam, generated via pion decay. These pions are the product of a proton beam striking a radiatively-cooled tungsten target. In order to maximize pion production and prevent target failure, the beam will have to be aligned with the target center to within 0.5 mm. The production target monitor (PTM) will ensure this alignment. The PTM consists of a series of proportional wire chambers (PWC’s) upstream and downstream of the production target. In this dissertation, I explain the requirements of this detector system and derive the decisions about which detector model to use and how they should be arranged from these requirements. After this, I describe my e xperience building the detectors and show an early use for them in the Mu2e proton beam. I also performed a study of the sensitivity and time resolution of this model of PWC and its electronics, and give the results here. I then describe a series of simulation campaigns which shed light on the interactions between the beam and the target, and how these interactions manifest on the downstream detectors. Finally, I give the target scanning procedure to be used to align the beam and target during experiment start up.

43 PARTICLE ACCELERATORS↗

A diagnosis system using object-oriented fault tree models

Spaceborne computing systems must provide reliable, continuous operation for extended periods. Due to weight, power, and volume constraints, these systems must manage resources very effectively. A fault diagnosis algorithm is described which enables fast and flexible diagnoses in the dynamic distributed computing environments planned for future space missions. The algorithm uses a knowledge base that is easily changed and updated to reflect current system status. Augmented fault trees represented in an object-oriented form provide deep system knowledge that is easy to access and revise as a system changes. Given such a fault tree, a set of failure events that have occurred, and a set of failure events that have not occurred, this diagnosis system uses forward and backward chaining to propagate causal and temporal information about other failure events in the system being diagnosed. Once the system has established temporal and causal constraints, it reasons backward from heuristically selected failure events to find a set of basic failure events which are a likely cause of the occurrence of the top failure event in the fault tree. The diagnosis system has been implemented in common LISP using Flavors.

Iverson, David L.↗

Carving out the end of the world or (superconformal bootstrap in six dimensions)

We bootstrap N=(1,0) superconformal field theories in six dimensions, by analyzing the four-point function of flavor current multiplets. By assuming E 8 flavor group, we present universal bounds on the central charge C T and the flavor central charge C J . Based on the numerical data, we conjecture that the rank-one E-string theory saturates the universal lower bound on C J , and numerically determine the spectrum of long multiplets in the rank-one E-string theory. We comment on the possibility of solving the higher-rank E-string theories by bootstrap and thereby probing M-theory on AdS 7 ×S 4 /Z 2 .

79 ASTRONOMY AND ASTROPHYSICS↗

A minimal supersymmetric SU(5) missing-partner model

We explore a missing-partner model based on the minimal SU(5) gauge group with 75, 50 and 50¯ Higgs representations, assuming a super-GUT CMSSM scenario in which soft supersymmetry-breaking parameters are universal at some high scale Min above the GUT scale MGUT. We identify regions of parameter space that are consistent with the cosmological dark matter density, the measured Higgs mass and the experimental lower limit on τ(p → K + ν). These constraints can be satisfied simultaneously along stop coannihilation strips in the super-GUT CMSSM with tanβ ~ 3.5–5 where the input gaugino mass m 1/2 ~15–25 TeV, corresponding after strong renormalization by the large GUT Higgs representations between M in and M GUT to m LSP ,m t ~ 1 ~ 2.5–5 TeV and m g ~ ~ 13–20 TeV, with the light-flavor squarks significantly heavier. We find that τ(p → K + ν) ≲ 3 × 10 34 years throughout the allowed range of parameter space, within the range of the next generation of searches with the JUNO, DUNE and Hyper-Kamiokande experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Gluon moment and parton distribution function of the pion from 𝑁 𝑓 = 2 +1 +1 lattice QCD

We present the first calculation of the pion gluon moment from lattice QCD in the continuum-physical limit. The calculation is done using clover fermions for the valence action with three pion masses, 220, 310 and 690 MeV, and three lattice spacings, 0.09, 0.12, and 0.15 fm, using ensembles generated by MILC Collaboration with 2+1+1 flavors of highly improved staggered quarks (HISQ). On the lattice, we nonperturbatively renormalize the gluon operator in RI/MOM scheme using the cluster-decomposition error reduction (CDER) technique to enhance the signal-to-noise ratio of the renormalization constant. We extrapolate the pion gluon moment to the continuum-physical limit and obtain ⟨𝑥⟩ 𝑔 = 0.394⁢(58) stat+NPR ⁢(39) mixing in the $\overline{MS}$ scheme at 2 GeV, with first error being the statistical error and uncertainties in nonperturbative renormalization, and the second being a systematic uncertainty estimating the effect of ignoring quark mixing. Our pion gluon momentum fraction has a central value lower than two recent single-ensemble lattice-QCD results near physical pion mass but is consistent with the recent global fits by JAM and xFitter and with most QCD-model estimates.

Astronomy & Astrophysics↗

Search for baryon junctions in e+A collisions at the electron ion collider

Constituent quarks in a nucleon are the essential elements in the standard “quark model” associated with the electric charge, spin, mass, and baryon number of a nucleon. Quantum chromodynamics (QCD) describes nucleon as a composite object containing current quarks (valence quarks and sea (anti-)quarks) and gluons. These subatomic elements and their interactions are known to contribute in complex ways to the overall nucleon spin and mass. In the early development of QCD theory in the 1970s, an alternative hypothesis postulated that the baryon number might manifest itself through a non-perturbative configuration of gluon fields forming a Y-shaped topology known as the gluon junction. In this work, we propose to test such hypothesis by measuring (i) the Regge intercept of the net-baryon distributions for e+(p)Au collisions, (ii) baryon and charge transport in the isobaric ratio between e+Ru and e+Zr collisions, and (iii) target flavor dependence of proton and antiproton yields at large rapidity, transported from the hydrogen and deuterium targets in e+p(d) collisions. Our study indicates that these measurements at the EIC can help determine what carries the baryon number.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Search for flavor-changing neutral-current couplings between the top quark and the Z boson with proton-proton collisions at s = 13 TeV with the ATLAS detector

A search for flavor-changing neutral-current couplings between a top quark, an up or charm quark, and a $Z$ boson is presented, using proton-proton collision data at $\sqrt{s}$ = 13 TeV collected by the ATLAS detector at the Large Hadron Collider. The analyzed data set corresponds to an integrated luminosity of 139 fb -1 . The search targets both single-top-quark events produced as $gq$ → $tZ$ (with $q$ = $u, c$) and top-quark-pair events, with one top quark decaying through the $t$ → $Zq$ channel. The analysis considers events with three leptons (electrons or muons), a $b$-tagged jet, possible additional jets, and missing transverse momentum. The data are found to be consistent with the background-only hypothesis and 95% confidence-level limits on the $t$ → $Zq$ branching ratios, assuming only tensor operators of the Standard Model effective field theory framework contribute to the $tZq$ vertices. These are 6.2 x 10 -5 (13 x 10 -5 ) for $t$ → $Zu$ ($t$ → $Zc$) for a left-handed $tZq$ coupling, and 6.6 x 10 -5 (12 x 10 -5 ) in the case of a right-handed coupling. These results are interpreted as 95% CL upper limits on the strength of the corresponding couplings, yielding limits for |${C}^{(13)*}_{uW}$| and |${C}^{(13)*}_{uB}$| (|${C}^{(31)}_{uW}$| and |${C}^{(31)}_{uB}$|) of 0.15 (0.16), and limits for |${C}^{(23)*}_{uW}$| and |${C}^{(23)*}_{uB}$| (|${C}^{(32)}_{uW}$| and |${C}^{(32)}_{uB}$|) of 0.22 (0.21), assuming a new-physics energy scale Λ NP of 1 TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Single-top-quark production in the t-channel at NNLO

We present a calculation of t-channel single-top-quark production and decay in the five-flavor scheme at NNLO. Our results resolve a disagreement between two previous calculations of this process that found a difference in the inclusive cross section at the level of the NNLO coefficient itself. We compare in detail with the previous calculations at the inclusive, differential and fiducial level including b-quark tagging at a fixed scale μ = m t . In addition, we advocate the use of double deep inelastic scattering (DDIS) scales ( μ 2 = Q 2 for the light-quark line and μ 2 = Q 2 + m t 2 for the heavy-quark line) that maximize perturbative stability and allow for robust scale uncertainties. All NNLO and NLOⓍNLO contributions for production and decay are included in the on-shell and vertex-function approximation. We present fiducial and differential results for a variety of observables used in Standard Model and Beyond Standard Model analyses, and find an important difference between the NLO and NNLO predictions of exclusive t + n-jet cross sections. Overall we find that NNLO corrections are crucial for a precise identification of the t-channel process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Strange Mesons and Gluonic Excitations

In the standard model of particle physics, the interactions between the fundamental constituents of nuclear matter, quarks and gluons, are governed by the theory of Quantum Chromodynamics (QCD). A central goal of nuclear physics is to understand how hadrons, such as protons and neutrons, are formed from these underlying quark and gluon degrees of freedom. A hadron is primarily constructed from three quarks or a quark-antiquark pair; however, the theory of QCD allows for much more exotic configurations. One of the predicted exotic configurations is known as a hybrid meson, which contains an excited gluonic field in addition to the usual quark-antiquark pair. This project aims to search for and study these gluonic excitations using the Gluonic Excitation (GlueX) experiment at Jefferson Lab in Newport News, VA. The discovery potential of the experiment will be significantly extended by studying the quark flavor composition of the meson spectrum through the completion and use of an enhanced detector to identify mesons containing strange quarks. The unprecedented statistical precision of the data collected at GlueX will allow us to search for a pattern of light-quark hybrid mesons, providing new insight into the interactions that bind the fundamental quarks and gluons into the hadrons we observe in nature.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Dark showers from Z-dark Z′ mixing

Abstract We discuss dark shower signals at the LHC from a dark QCD sector, containing GeV-scale dark pions. The portal with the Standard Model is given by the mixing of theZboson with a darkZ′ coupled to the dark quarks. Both mass and kinetic mixings are included, but the mass mixing is the essential ingredient, as it is the one mediating visible decays of the long-lived dark pions. We focus especially on the possibility that the darkZ′ islighterthan theZ. Indirect constraints are dominated by electroweak precision tests, which we thoroughly discuss, showing that bothZ-pole and low-energy observables are important. We then recast CMS and LHCb searches for displaced dimuon resonances to dark shower signals initiated by the production of on-shellZorZ′, where the visible signature is left by a dark pion decaying toμ + μ − . We demonstrate how dark shower topologies have already tested new parameter space in Run 2, reaching better sensitivity on a light darkZ′ compared to the flavor-changing decays ofBmesons, which can produce a single dark pion at a time, and the electroweak precision tests.

Physics↗

Experimental Highlights: Heavy Quark Physics in Heavy-Ion Collisions at RHIC

The discovery at RHIC of large high-p T suppression and flow of electrons from heavy quarks flavors have altered our view of the hot and dense matter formed in central Au + Au collisions at √s NN = 200 GeV. These results suggest a large energy loss and flow of heavy quarks in the hot, dense matter. In recent years, the RHIC experiments upgraded the detectors; (1) PHENIX Collaboration installed silicon vertex tracker (VTX) at midrapidity region and forward silicon vertex tracker (FVTX) at the forward rapidity region, and (2) STAR Collaboration installed the heavy flavor tracker (HFT) and the muon telescope detector (MTD) both at the mid-rapidity region. The PHENIX experiments established measurements of ψ (1S ) and ψ (2S ) production as a function of system size, p + p, p + Al, p + Au, and 3 He + Au collisions at √s NN = 200 GeV. In p/ 3 He + A collisions at forward rapidity, we observe no difference in the ψ (2S )/ψ (1S ) ratio relative to p + p collisions. At backward rapidity, where the comoving particle density is higher, we find that the ψ (2S ) is preferentially suppressed by a factor of two. STAR Collaboration presents the first J/ ψ measurements in the di-muon decay channel in Au + Au at √s NN = 200 GeV at mid-rapidity. In conclusion, we observe a clear J/ψ R AA suppression and qualitatively well described by transport models, including dissociation and regeneration simultaneously.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Antineutrino Oscillations and a Search for Non-standard Interactions with the MINOS

MINOS searches for neutrino oscillations using the disappearance of muon neutrinos from the NuMI beam at Fermilab between two detectors. The Near Detector, located near the source, measures the beam composition before flavor change occurs. The energy spectrum is measured again at the Far Detector after neutrinos travel a distance. The mixing angle and mass splitting between the second and third mass states are extracted from the energy dependent difference between the spectra at the two detectors. NuMI is able to produce an antineutrino-enhanced beam as well as a neutrino-enhanced beam. Collecting data in antineutrino-mode allows the direct measurement of antineutrino oscillation parameters. From the analysis of the antineutrino mode data we measure $|\Delta\bar{m}^{2}_{\text{atm}}| = 2.62^{+0.31}_{-0.28}\times10^{-3}\text{eV}^{2}$ and $\sin^{2}(2\bar{\theta})_{23} = 0.95^{+0.10}_{-0.11}$, which is the most precise measurement of antineutrino oscillation parameters to date. A difference between neutrino and antineutrino oscillation parameters may indicate new physics involving interactions that are not part of the Standard Model, called non-standard interactions, that alter the apparent disappearance probability. Collecting data in neutrino and antineutrino mode independently allows a direct search for non-standard interactions. In this dissertation non-standard interactions are constrained by a combined analysis of neutrino and antineutrino datasets and no evidence of such interactions is found.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Nucleon Structure Studies at Jefferson Lab and the Electron Ion Collider

The research programs of Thomas Jefferson Laboratory (JLab) and the future Electron- Ion Collider (EIC) focus on one of the main goals of strong interaction studies : understanding the structure of nucleons in terms of the quarks and gluons composing them. Their structure is encoded in functions such as Generalized Parton Distributions (GPDs), which describe how quarks and gluons’ transverse position and longitudinal momentum are distributed inside nucleons. GPDs allow to obtain three-dimensional pictures of nucleons and to understand some of their fundamental properties, such as their internal pressure or the emergence of their spin from the dynamics of the partons composing them. At JLab and the EIC, electron beams are used to probe nucleons. Measurement of reactions such as Deeply Virtual Compton Scattering (DVCS) allows access to GPDs. The first longitudinally polarized-target experiment of the CLAS12 program at Jlab took place in 2022-2023. Combining polarized electron beams and nucleon targets, this experiment offers unique access to observables that allow the measurement of different types of GPDs. In particular, the DVCS beam- and target-spin asymmetries for protons and neutrons in deuterium will be measured for the first time. They give access to kinds of GPDs that are still poorly known, and the comparison between proton and neutron data will allow the extraction of the flavor dependence of the structure of nucleons. Specific analysis methods have been implemented to work with a polarized nuclear target and are presented in this thesis. These methods allow to obtain preliminary results for the asymmetries, waiting for the complete statistics to be available. In the long term, the experimental program for the EIC has been established with a strong emphasis on the measurement of the structure of nucleons at high energy. Measurements of reactions such as DVCS impose strict requirements on the electromagnetic calorimeter that will allow to measure the energy of the scattered electrons and photons. This calorimeter, which is under development, will be based on scintillating crystals read by Silicon Photomultipliers (SiPMs). A new type of glass-based scintillating material was tested, evaluating the possibilities to meet the technical requirements concerning their light yield and resistance to radiation damage in particular. Several models of SiPMs have been characterized, demonstrating they can operate over the vast energy range necessary to address the physics case at the EIC and providing guidelines for developing their readout electronics.

Pilleux, Noemie↗