arXiv subjects

Collaboration

Publications and source records attributed to Collaboration.

15 recordsLinked to original sources

arXiv2026

Measurement of the $^3$He Spin Structure Functions and Their Moments at Low Q$^2$

We report measurements of spin-dependent electron scattering from a polarized $^3$He target, $\vec{^3\textrm{He}}(\vec{e},e')X$, performed at the Thomas Jefferson National Accelerator Facility (Jefferson Lab). The $^3$He spin-dependent virtual-photoabsorption cross sections $\sigma_{TT}$ and $\sigma_{LT}$, or equivalently the spin structure functions $g_1$ and $g_2$, and their moments were extracted for $0.032 \leq Q^2 \leq 0.23$~GeV$^2$, with coverage from the two-body breakup threshold through the nucleon-resonance region. The moment $I_1(Q^2)$ reaches a plateau below $Q^2 \simeq 0.1$~GeV$^2$, consistent with the Gerasimov--Drell--Hearn (GDH) expectation, while the moment $I_{TT}(Q^2)$, still dominated by the finite-virtuality breakup response, peaks at $Q^2 \simeq 0.1$~GeV$^2$ and turns toward the expected GDH value. Together, the two moments constitute the first observation of a nucleus approaching its GDH sum-rule value at the real-photon point. The moments $I_2(Q^2)$ and $I_{LT}(Q^2)$ yield, respectively, the lowest-$Q^2$ nuclear test of the Burkhardt--Cottingham sum rule and the first nuclear test of the Schwinger sum rule. Besides testing fundamental sum rules, these data provide stringent benchmarks for ab initio calculations of the spin structure of light nuclei.

nucl-ex↗

arXiv2025

A multi-modal infant-based metric for choosing the best supernova

We present a comparative study of 22 core-collapse supernovae (SNe), selected to explore a novel, multidimensional ranking scheme aimed at identifying the best supernova. Each SN is evaluated based on three principal criteria: (1) inferred explosion energy derived from light curve modeling and spectroscopic indicators; (2) an aesthetic score assigned to the SN host galaxy following transformation into a human face using a generative visual model (Midjourney v5); and (3) final ranking by Claud.IA, a 6-month-old infant trained to select the best SN via repeated exposure to curated SN images. We define and normalize all criteria to ensure statistical consistency across the sample, with particular attention paid to the biases inherent in infant-based classification models. The top five SNe exhibit both high explosion energies (E > 1e51 erg) and extremely cool host galaxies (post transformation), with Claud.IA showing strong preferences toward galaxies exhibiting symmetric facial morphology and prominent spiral arms. Final application of Claud.IA identified the best supernova in our sample as SN 2022joj. Our study demonstrates the feasibility of incorporating human-machine hybrid aesthetic judgment and early developmental cognition into astrophysical classification, and raises intriguing questions about the nature of bestness in cosmic explosions. Additional follow-up is encouraged.

astro-ph.HE↗

arXiv2024

International comparison of optical frequencies with transportable optical lattice clocks

Optical clocks have improved their frequency stability and estimated accuracy by more than two orders of magnitude over the best caesium microwave clocks that realise the SI second. Accordingly, an optical redefinition of the second has been widely discussed, prompting a need for the consistency of optical clocks to be verified worldwide. While satellite frequency links are sufficient to compare microwave clocks, a suitable method for comparing high-performance optical clocks over intercontinental distances is missing. Furthermore, remote comparisons over frequency links face fractional uncertainties of a few $10^{-18}$ due to imprecise knowledge of each clock's relativistic redshift, which stems from uncertainty in the geopotential determined at each distant location. Here, we report a landmark campaign towards the era of optical clocks, where, for the first time, state-of-the-art transportable optical clocks from Japan and Europe are brought together to demonstrate international comparisons that require neither a high-performance frequency link nor information on the geopotential difference between remote sites. Conversely, the reproducibility of the clocks after being transported between countries was sufficient to determine geopotential height offsets at the level of 4 cm. Our campaign paves the way for redefining the SI second and has a significant impact on various applications, including tests of general relativity, geodetic sensing for geosciences, precise navigation, and future timing networks.

physics.atom-ph↗

arXiv2024

Helicity-dependent parton distribution functions at next-to-next-to-leading order accuracy from inclusive and semi-inclusive deep-inelastic scattering data

We present MAPPDFpol1.0, a new determination of the helicity-dependent parton distribution functions (PDFs) of the proton from a set of longitudinally polarised inclusive and semi-inclusive deep-inelastic scattering data. The determination includes, for the first time, next-to-next-to-leading order QCD corrections to both processes, and is carried out in a framework that combines a neural-network parametrisation of PDFs with a Monte Carlo representation of their uncertainties. We discuss the quality of the determination, in particular its dependence on higher-order corrections, on the choice of data set, and on theoretical constraints.

hep-ph↗

arXiv2021

Projected sensitivity of the LUX-ZEPLIN (LZ) experiment to the two-neutrino and neutrinoless double beta decays of $^{134}$Xe

The projected sensitivity of the LUX-ZEPLIN (LZ) experiment to two-neutrino and neutrinoless double beta decay of $^{134}$Xe is presented. LZ is a 10-tonne xenon time projection chamber optimized for the detection of dark matter particles, that is expected to start operating in 2021 at Sanford Underground Research Facility, USA. Its large mass of natural xenon provides an exceptional opportunity to search for the double beta decay of $^{134}$Xe, for which xenon detectors enriched in $^{136}$Xe are less effective. For the two-neutrino decay mode, LZ is predicted to exclude values of the half-life up to 1.7$\times$10$^{24}$ years at 90% confidence level (CL), and has a three-sigma observation potential of 8.7$\times$10$^{23}$ years, approaching the predictions of nuclear models. For the neutrinoless decay mode LZ, is projected to exclude values of the half-life up to 7.3$\times$10$^{24}$ years at 90% CL.

physics.ins-det↗

arXiv2020

Frequency Ratio Measurements with 18-digit Accuracy Using a Network of Optical Clocks

Atomic clocks occupy a unique position in measurement science, exhibiting higher accuracy than any other measurement standard and underpinning six out of seven base units in the SI system. By exploiting higher resonance frequencies, optical atomic clocks now achieve greater stability and lower frequency uncertainty than existing primary standards. Here, we report frequency ratios of the $^{27}$Al$^+$, $^{171}$Yb and $^{87}$Sr optical clocks in Boulder, Colorado, measured across an optical network spanned by both fiber and free-space links. These ratios have been evaluated with measurement uncertainties between $6\times10^{-18}$ and $8\times10^{-18}$, making them the most accurate reported measurements of frequency ratios to date. This represents a critical step towards redefinition of the SI second and future applications such as relativistic geodesy and tests of fundamental physics.

physics.atom-ph↗

arXiv2019

A Roadmap for Astrophysics and Cosmology with High-Redshift 21 cm Intensity Mapping

In this white paper, we lay out a US roadmap for high-redshift 21 cm cosmology (30 < z < 6) in the 2020s. Beginning with the currently-funded HERA and MWA Phase II projects and advancing through the decade with a coordinated program of small-scale instrumentation, software, and analysis projects targeting technology development, this roadmap incorporates our current best understanding of the systematics confronting 21 cm cosmology into a plan for overcoming them, enabling next-generation, mid-scale 21 cm arrays to be proposed late in the decade. Submitted for consideration by the Astro2020 Decadal Survey Program Panel for Radio, Millimeter, and Submillimeter Observations from the Ground as a Medium-Sized Project.

astro-ph.IM↗

arXiv2019

Estimating the sample mean and standard deviation from commonly reported quantiles in meta-analysis

Researchers increasingly use meta-analysis to synthesize the results of several studies in order to estimate a common effect. When the outcome variable is continuous, standard meta-analytic approaches assume that the primary studies report the sample mean and standard deviation of the outcome. However, when the outcome is skewed, authors sometimes summarize the data by reporting the sample median and one or both of (i) the minimum and maximum values and (ii) the first and third quartiles, but do not report the mean or standard deviation. To include these studies in meta-analysis, several methods have been developed to estimate the sample mean and standard deviation from the reported summary data. A major limitation of these widely used methods is that they assume that the outcome distribution is normal, which is unlikely to be tenable for studies reporting medians. We propose two novel approaches to estimate the sample mean and standard deviation when data are suspected to be non-normal. Our simulation results and empirical assessments show that the proposed methods often perform better than the existing methods when applied to non-normal data.

stat.ME↗

arXiv2018

Nonperturbative investigations of SU(3) gauge theory with eight dynamical flavors

We present our lattice studies of SU(3) gauge theory with $N_f$ = 8 degenerate fermions in the fundamental representation. Using nHYP-smeared staggered fermions we study finite-temperature transitions on lattice volumes as large as $L^3 \times N_t = 48^3 \times 24$, and the zero-temperature composite spectrum on lattice volumes up to $64^3 \times 128$. The spectrum indirectly indicates spontaneous chiral symmetry breaking, but finite-temperature transitions with fixed $N_t \leq 24$ enter a strongly coupled lattice phase as the fermion mass decreases, which prevents a direct confirmation of spontaneous chiral symmetry breaking in the chiral limit. In addition to the connected spectrum we focus on the lightest flavor-singlet scalar particle. We find it to be degenerate with the pseudo-Goldstone states down to the lightest masses reached so far by non-perturbative lattice calculations. Using the same lattice approach, we study the behavior of the composite spectrum when the number of light fermions is changed from eight to four. A heavy flavor-singlet scalar in the 4-flavor theory affirms the contrast between QCD-like dynamics and the low-energy behavior of the 8-flavor theory.

hep-lat↗

arXiv2012

Mu2e Conceptual Design Report

Mu2e at Fermilab will search for charged lepton flavor violation via the coherent conversion process mu- N --> e- N with a sensitivity approximately four orders of magnitude better than the current world's best limits for this process. The experiment's sensitivity offers discovery potential over a wide array of new physics models and probes mass scales well beyond the reach of the LHC. We describe herein the conceptual design of the proposed Mu2e experiment. This document was created in partial fulfillment of the requirements necessary to obtain DOE CD-1 approval, which was granted July 11, 2012.

physics.ins-det↗

arXiv2009

Status of the NA61 (SHINE) experiment at CERN

A precise measurement of the hadron production from interactions of 30 GeV protons on carbon target is performed by NA61 (SHINE) experiment at the CERN SPS. The inclusive spectra of pions and kaons on the carbon target obtained from NA61 measurements constrain the neutrino flux in the T2K long baseline neutrino oscillation experiment at J-PARC, Japan. The article presents description of the NA61 apparatus together with the preliminary results from the pilot 2007 run.

hep-ex↗

arXiv2006

A U-band survey of brown dwarfs in the Taurus Molecular Cloud with the XMM-Newton Optical/UV Monitor

We aim to characterize the U-band variability of young brown dwarfs in the Taurus Molecular Cloud and discuss its origin. We used the XMM-Newton Extended Survey of the Taurus Molecular Cloud, where a sample of 11 young bona fide brown dwarfs (spectral type later than M6) were observed simultaneously in X-rays with XMM-Newton and in the U-band with the XMM-Newton Optical/UV Monitor (OM). We obtained upper limits to the U-band emission of 10 brown dwarfs (U>19.6-20.6 mag), whereas 2MASSJ04141188+2811535 was detected in the U-band. Remarkably, the magnitude of this brown dwarf increased regularly from U~19.5 mag at the beginning of the observation, peaked 6h later at U~18.4 mag, and then decreased to U~18.65 mag in the next 2h. The first OM U-band measurement is consistent with the quiescent level observed about one year later thanks to ground follow-up observations. This brown dwarf was not detected in X-rays by XMM-Newton during the OM observation. We discuss the possible sources of U-band variability for this young brown dwarf, namely a magnetic flare, non-steady accretion onto the substellar surface, and rotational modulation of a hot spot. We conclude that this event is related to accretion from a circumsubstellar disk, where the mass accretion rate was about a factor of 3 higher than during the quiescent level.

astro-ph↗

arXiv2006

Final Report of the Muon E821 Anomalous Magnetic Moment Measurement at BNL

We present the final report from a series of precision measurements of the muon anomalous magnetic moment, a_mu = (g-2)/2. The details of the experimental method, apparatus, data taking, and analysis are summarized. Data obtained at Brookhaven National Laboratory, using nearly equal samples of positive and negative muons, were used to deduce a_mu(Expt) = 11 659 208.0(5.4)(3.3) x 10^-10, where the statistical and systematic uncertainties are given, respectively. The combined uncertainty of 0.54 ppm represents a 14-fold improvement compared to previous measurements at CERN. The standard model value for a_mu includes contributions from virtual QED, weak, and hadronic processes. While the QED processes account for most of the anomaly, the largest theoretical uncertainty, ~0.55 ppm, is associated with first-order hadronic vacuum polarization. Present standard model evaluations, based on e+e- hadronic cross sections, lie 2.2 - 2.7 standard deviations below the experimental result.

hep-ex↗

arXiv2005

Measurement of Pressure Dependent Fluorescence Yield of Air: Calibration Factor for UHECR Detectors

In a test experiment at the Final Focus Test Beam of the Stanford Linear Accelerator Center, the fluorescence yield of 28.5 GeV electrons in air and nitrogen was measured. The measured photon yields between 300 and 400 nm at 1 atm and 29 deg C are Y(760 Torr, air) = 4.42 +/- 0.73 and Y(760 Torr, nitrogen) = 29.2 +/- 4.8 photons per electron per meter. Assuming that the fluorescence yield is proportional to the energy deposition of a charged particle traveling through air, good agreement with measurements at lower particle energies is observed.

astro-ph↗

arXiv1997

Inclusive Dielectron Cross Sections in p+p and p+d Interactions at Beam Energies from 1.04 to 4.88 GeV

Measurements of dielectron production in p+p and p+d collisions with beam kinetic energies from 1.04 to 4.88 GeV are presented. The differential cross section is presented as a function of invariant pair mass, transverse momentum, and rapidity. The shapes of the mass spectra and their evolution with beam energy provide information about the relative importance of the various dielectron production mechanisms in this energy regime. The p+d to p+p ratio of the dielectron yield is also presented as a function of invariant pair mass, transverse momentum, and rapidity. The shapes of the transverse momentum and rapidity spectra from the p+d and p+p systems are found to be similar to one another for each of the beam energies studied. The beam energy dependence of the integrated cross sections is also presented.

nucl-ex↗