Fermi National Laboratory Research Articles

Minimal dark matter model for muon g−2 with scalar lepton partners up to the TeV scale

The E989 experiment at the Fermi National Laboratory reported a $4.2\ensuremath{\sigma}$ discrepancy between the measured magnetic dipole moment of the muon, and its prediction in the Standard Model (SM). In this study, we address the anomaly by considering a minimal and generic extension to the SM which also provides for a dark matter (DM) candidate. The extra states in this framework are: a SM singlet Majorana fermion, referred to as the Bino, playing the role of DM; and muonic scalars, referred to as sleptons. The couplings between the sleptons, SM muons and the Bino can account for the muon $g\ensuremath{-}2$ anomaly if the scalar muon partners, or smuons, mix chirality. On the other hand, the DM relic density is satisfied primarily through coannihilation effects involving the Bino and the lighter sleptons. The viable parameter space of our model includes regions with relatively light coannihilating particles, similar to what has been found in previous scans of the Minimal Supersymmetric Standard Model (MSSM). Relaxing the assumption of minimal flavor violation typically assumed in the MSSM, we see that scenarios with sizable smuon mixing and large mass splittings between the smuons can satisfy both the muon $g\ensuremath{-}2$ anomaly and the DM relic density for coannihilating particle masses up to and beyond the TeV scale. When we specify the origin of the left-right smuon mixing to be trilinear couplings between the smuons and the SM Higgs boson, the constraints on these scenarios arising from perturbative unitarity and electroweak vacuum stability confine the coannihilating particle masses to be $\ensuremath{\lesssim}1\text{ }\text{ }\mathrm{TeV}$. We demonstrate that next generation direct detection experiments are only marginally sensitive to the viable parameter space of our model, and, thus, a future lepton collider could be the essential probe necessary to distinguish our model from other solutions to the muon $g\ensuremath{-}2$ anomaly which involve extra states beyond the SM.

Recent three-flavor neutrino oscillation results from the NOvA experiment

NOvA is a long-baseline experiment studying primarily neutrino oscillations in the NuMI beam from Fermi National Laboratory (FNAL), USA. It consists of two functionally identical, finely granulated detectors which are separated by 810 km and situated 14.6 mrad off the NuMI beam axis from FNAL. By measuring the transition probabilities P(vμ → ve ) and P(vμ → vμ ), NOvA is able to probe the following parameters: , the mixing angle θ 23, the CP violating phase δCP and the neutrino mass hierarchy. This document is devoted to the latest NOvA measurements of the neutrino oscillation parameters using neutrino and antineutrino disappearance and appearance obtained in 2020.

HEPCloud, an Elastic Hybrid HEP Facility using an Intelligent Decision Support System

HEPCloud is rapidly becoming the primary system for provisioning compute resources for all Fermilab-affiliated experiments. In order to reliably meet the peak demands of the next generation of High Energy Physics experiments, Fermilab must plan to elastically expand its computational capabilities to cover the forecasted need. Commercial cloud and allocation-based High Performance Computing (HPC) resources both have explicit and implicit costs that must be considered when deciding when to provision these resources, and at which scale. In order to support such provisioning in a manner consistent with organizational business rules and budget constraints, we have developed a modular intelligent decision support system (IDSS) to aid in the automatic provisioning of resources spanning multiple cloud providers, multiple HPC centers, and grid computing federations. In this paper, we discuss the goals and architecture of the HEPCloud Facility, the architecture of the IDSS, and our early experience in using the IDSS for automated facility expansion both at Fermi and Brookhaven National Laboratory.

N-Doped Surfaces of Superconducting Niobium Cavities as a Disordered Composite

The Q-factor of superconducting accelerating cavities can be substantially improved by a special heat treatment under N2 atmosphere (N-doping). Recent experiments at Fermi National Laboratory investigated the dependence of Q on the RF frequency and showed, unexpectedly, both an increase and a decrease with the RF field amplitude. This paper shall explain this finding by extending a previously proposed model founded on the two fluid model of RF losses, percolation and the proximity effect in a disordered composite.

Cosmic ray topography

Cosmic ray muons are produced when high energy particles interact with nuclei in Earth's atmosphere. Muons make up the majority of charged particles that reach sea level and are the only particles (apart from neutrinos) that can penetrate to significant depths underground. The muon flux underground decreases approximately exponentially as a function of depth. We use a cosmic ray detector developed by the QuarkNet Program at Fermi National Laboratory to map the topography of the mountain above an abandoned Pennsylvania Turnpike tunnel by analyzing muon flux at different rock overburdens. Cosmic ray muons have been used in this capacity before to search for hidden chambers in pyramids and for mapping volcanoes. This study provides a unique field experience to learn about particle physics and particle detectors, which could be of interest to students and teachers in physics.

Design and Manufacture of the Conduction Cooled Torus Coils for The Jefferson Laboratory 12-GeV Upgrade

The design of the 12-GeV torus required the construction of six superconducting coils with a unique geometry required for the experimental needs of Jefferson Laboratory Hall B. Each of these coils consists of 234 turns of copper-stabilized superconducting cable conduction cooled by 4.6 K helium gas. The finished coils are each roughly 2 × 4 × 0.05 m and supported in an aluminum coil case. Because of its geometry, new tooling and manufacturing methods had to be developed for each stage of construction. The tooling was designed and developed while producing a practice coil at Fermi National Laboratory. This paper describes the tooling and manufacturing techniques required to produce the six production coils and two spare coils required by the project. Project status and future plans are also presented.

Large size GEM for Super Bigbite Spectrometer (SBS) polarimeter for Hall A 12 GeV program at JLab

We report on the R&D effort in the design and construction of a large size Gas Electron Multiplier (GEM) for the Proton Polarimeter Back Tracker (BT) of the Super Bigbite Spectrometer (SBS) in Hall A at Thomas Jefferson National Laboratory (JLab). The SBS BT GEM trackers consist of two sets of five large GEM chambers of size 60×200cm2. The GEM chamber is a vertical stack of four GEM modules, each with an active area of 60×50cm2. We have built and tested several prototypes and the construction of GEM modules for SBS BT is ongoing. We describe in this paper the design and construction of the GEM module prototype as well as the preliminary results on performance from tests carried out in our detector lab and during test beam at Fermi National Laboratory (Fermilab).

G - 2 AT FNAL

The g - 2 experiment at Fermi National Laboratory is planned to refine previous measurements of the anomalous magnetic moment of the muon, reducing systematic errors and generate constraints on possible physics beyond the standard model. This paper describes some of the ways in which a four-fold reduction in systematic errors will be achieved.

Precise measurements of the hadronic cross sections with the CMD-3 and SND detectors at the VEPP-2000e+e−collider

It’s good known the difference in 3.5 sigma between the muon (g – 2) experimental result and its calculation in Standard Model. To clarify this intriguing discrepancy the new stage of muon (g – 2) measurement is under preparation at Fermi National Laboratory. On other hand, regular data taking for measurements of hadron cross section production in e + e − annihilations is under way since December 2010 at the electron-positron collider VEPP-2000 with the CMD-3 and SND detectors. The collected data sample corresponds to about 60 inverse picobarns of integrated luminosity per detector in the energy range from 0.32 up to 2 GeV. Preliminary analysis of various hadronic cross sections has been performed.

Elastic scattering with the MINERνA experiment

The Main Injector Experiment ν-A (MINERνA) located at Fermi National Laboratory will measure neutrino cross sections, nuclear effects from a broad range of nuclear targets and a variety of other neutrino interactions. Neutrino elastic scattering will be one of the first focuses of the MINERA collaboration; these measurements will be an important input to current and future neutrino oscillation experiments. Results of the charged current quasi-elastic channel exposure in anti-neutrino NuMI running are presented. Future elastic scattering results, both charged current and neutral current, in anti-neutrino and neutrino exposures are also discussed.

G-2 of the Muon

The experimental value a $_{\mu}^{\rm exp}$ for the muon magnetic anomaly measured at the Brookhaven National Laboratory (BNL), Upton, USA, and the latest theoretical value a $_{\mu}^{\rm theo}$ based on a number of calculations and auxiliary experiments differ today by 3.3 standard deviations. Discrepancies between different independent approaches towards the theoretical value could recently be removed and had yielded a consistent value for a $_{\mu}^{\rm theo}$ . At the Fermi National Laboratory (Fermilab), Batavia, USA, a new experiment has been approved which aims to improve the present experimental uncertainty by a factor of about five. At this level the muon magnetic anomaly is superior in sensitivity to, e.g., LHC concerning tests of several speculative models beyond standard theory. The new experiment relies in the essential parts on concepts proven at BNL such as a muon storage ring at 1.45 T field to store muons at 3.1 GeV/c momentum and field magnetometry based on NMR in water. At Fermilab predominantly a significantly higher number of muons can be exploited.

Small-xnuclear shadowing from diffractive scattering

We calculate nuclear shadowing ratios at small Bjorken-$x$ for nuclei in the mass range $3lAl239$ in the framework of a generalized form of the Gribov theory. The diffractive dissociation cross sections needed as inputs are taken from the FNAL (Fermi National Laboratory) and HERA (Hadron-Electron Ring Accelerator) experiments. Our calculations cover a wide range of energies between 12.8 and 231 GeV. The effects of the inclusion of subleading Reggeons on nuclear shadowing are investigated. At lower energies our results are compared to available data from the New Muon Collaboration (NMC) and E665 Collaboration (E665) experiments at $x\ensuremath{\simeq}{10}^{\ensuremath{-}4}$. At higher energies subleading Reggeons are found to contribute significantly to nuclear shadowing.

Long-Baseline Accelerator Experiments in the United States

The status and future of long-baseline accelerator experiments in the United States is described. Discussed experiments will exploit the NuMI beamline, due to deliver the first neutrinos at the beginning of 2005. A short description of this flexible, high-intensity neutrino beamline at the Fermi National Laboratory is provided.

Calibration of saturated liquid helium weir flowmeter at Fermilab

The flow of saturated liquid helium at 4.2 K was studied in a unique weir flowmeter mounted inside a duct. The objective was to develop a calibration for helium flow rate in the weir, and thereby, making it a viable flowmeter. The weir flowmeter was tested in a liquid helium system at Fermi National Laboratory used for cooling the superconducting magnets in the experimental areas of the site. Unlike for open channel weir devices, the calibration of this flowmeter was influenced by both the liquid flow through the weir notch and the vapor flow over it. The results of this study and the calibration are presented taking into account effects of both liquid and vapor.

Temperature compensation in hybrid magnets with application to the Fermilab stacker and recycler ring dipole design

Design theory of hybrid (permanent magnet plus iron) accelerator magnets with application to the proposed permanent magnet recycler and stacker rings at the Fermi National Laboratory is presented. Field stability in such devices requires that changes in the strength of the permanent magnet material with temperature be compensated. Field tuning techniques, including those employing variable capacitance between energized pole and magnet yoke and those employing variable energization of magnet pole pieces, are described. Mechanical configurations capable of achieving temperature compensation passively, including use of expanding liquids/gases and bimetallic springs are outlined. Active configurations, relying on a actuator, in addition to temperature compensation, have the additional benefit of enabling magnet tuning about a nominal operating field level.

A trigger for the Fermilab E760 lead-glass calorimeter

The E760 #1 #1 Fermilab, Ferrara, Genova, U.C. Irvine, Northwestern, Penn. State, Torino collaboration. experiment at Fermi National Laboratory has been commissioned to study electromagnetic decay channels of charmonium states. A trigger has been built for the 1280-element lead-glass calorimeter to facilitate the study of all-neutral decay modes. The trigger has also proven to be extremely useful for charged electromagnetic final states. The trigger has been successfully deployed and has shown itself to be reliable and highly efficient. The design and performance of this trigger are described in detail.

The microvax-based data acquisition system for DØ

A large array of MicroVAX computers will be used for high-speed data acquisition and online filtering in the D0 experiment at Fermi National Laboratory. We describe this system, as well as several smaller data acquisition systems now operational, with particular emphasis on the control and communication software. The computers in this array will run under VAXELN.

Measurement of the nuclear enhancement in high-Et and jet event production.

Propertiea of eventa produced with high values of transverse energy (Et) in 800 GeV/c proton-nucleus collieions are presented. Both full-arimuth and limited aperture high Et triggers were wed to melect event6 from six targets (H, Be, C, Al, Cu, and Pb). The events were collected using the large acceptance Fermilab multiparticle spectrometer that recorded almost 95% of the incoming beam energy. The A dependence of the crow sectiona at a given Rt W(UI parameterixed M Aa . The value of a increases from 0.7 at low Et to a plateau at high Et of approximately 1.6. The high Et value of a is slightly amaller for the limited aperture triggers. A strong dependence of (1 on the event structure was observed; yet-like” events exhibit an A dependence consistent with a-1.0, while for more isotropic events a ia much larger. This observation is consistent with the expected behavior for jet production in pA colliaione. (a) Present address: Dept. of Physics, University of Michigan-Flint, Flint, MI 48502 (*) Present address: Inst. of Nucl. Physics, Novi Sad, Yugoslavia cc) Present address: Dept. of Physics, Univ. of Ariaona, Tucson AZ 85721 cd) Present address: A T & T Bell Laboratories, Naperville, IL, 80540 cc) Present address: Fermi National laboratory, Batavia, IL 60510 (f) Present address: Dept. of Physics, Univ. of Roeheater, NY 14267 (g) Present address: Tata Inst. of Fundamental Research, Bombay, India 400005

On the Designing of a Science Museum and a Particle Accelerator Laboratory: Interviews with Frank Oppenheimer and Robert Wilson

Two interviews with physicists Frank Oppenheimer and Robert Wilson illuminate one another. Each tells the story of how major American institutions, San Francisco’s Exploratorium and The Fermi National Laboratory in Illinois, were consciously infused with an underlying vision that places science, art, and nature in an aesthetic continuum.

The effect of bone on dose distributions produced by the Fermi National Laboratory fast-neutron beam.

The dose distortion produced by bone during fast-neutron therapy was studied using a target-to-skin distance of 153 cm, with beams 10 x 10 field size at the surface of a phantom. Doses were measured using several muscle-equivalent ionization chambers in the phantom. Results showed that the dose was reduced by interposing bone-equivalent material between the point in question and the surface of the phantom.