arXiv subjects

J. M. Conrad

Publications and source records attributed to J. M. Conrad.

At least 325 records · Page 18Linked to original sources

arXiv2014

Advanced Scintillator Detector Concept (ASDC): A Concept Paper on the Physics Potential of Water-Based Liquid Scintillator

The recent development of Water-based Liquid Scintillator (WbLS), and the concurrent development of high-efficiency and high-precision-timing light sensors, has opened up the possibility for a new kind of large-scale detector capable of a very broad program of physics. The program would include determination of the neutrino mass hierarchy and observation of CP violation with long-baseline neutrinos, searches for proton decay, ultra-precise solar neutrino measurements, geo- and supernova neutrinos including diffuse supernova antineutrinos, and neutrinoless double beta decay. We outline here the basic requirements of the Advanced Scintillation Detector Concept (ASDC), which combines the use of WbLS, doping with a number of potential isotopes for a range of physics goals, high efficiency and ultra-fast timing photosensors, and a deep underground location. We are considering such a detector at the Long Baseline Neutrino Facility (LBNF) far site, where the ASDC could operate in conjunction with the liquid argon tracking detector proposed by the LBNE collaboration. The goal is the deployment of a 30-100 kiloton-scale detector, the basic elements of which are being developed now in experiments such as WATCHMAN, ANNIE, SNO+, and EGADS.

physics.ins-det↗

arXiv2014

Ortho-positronium observation in the Double Chooz Experiment

The Double Chooz experiment measures the neutrino mixing angle $θ_{13}$ by detecting reactor $\barν_e$ via inverse beta decay. The positron-neutron space and time coincidence allows for a sizable background rejection, nonetheless liquid scintillator detectors would profit from a positron/electron discrimination, if feasible in large detector, to suppress the remaining background. Standard particle identification, based on particle dependent time profile of photon emission in liquid scintillator, can not be used given the identical mass of the two particles. However, the positron annihilation is sometimes delayed by the ortho-positronium (o-Ps) metastable state formation, which induces a pulse shape distortion that could be used for positron identification. In this paper we report on the first observation of positronium formation in a large liquid scintillator detector based on pulse shape analysis of single events. The o-Ps formation fraction and its lifetime were measured, finding the values of 44$\%$ $\pm$ 12$\%$ (sys.) $\pm$ 5$\%$ (stat.) and $3.68$ns $\pm$ 0.17ns (sys.) $\pm$ 0.15ns (stat.) respectively, in agreement with the results obtained with a dedicated positron annihilation lifetime spectroscopy setup.

physics.ins-det↗

arXiv2014

Precision Muon Reconstruction in Double Chooz

We describe a muon track reconstruction algorithm for the reactor anti-neutrino experiment Double Chooz. The Double Chooz detector consists of two optically isolated volumes of liquid scintillator viewed by PMTs, and an Outer Veto above these made of crossed scintillator strips. Muons are reconstructed by their Outer Veto hit positions along with timing information from the other two detector volumes. All muons are fit under the hypothesis that they are through-going and ultrarelativistic. If the energy depositions suggest that the muon may have stopped, the reconstruction fits also for this hypothesis and chooses between the two via the relative goodness-of-fit. In the ideal case of a through-going muon intersecting the center of the detector, the resolution is ~40 mm in each transverse dimension. High quality muon reconstruction is an important tool for reducing the impact of the cosmogenic isotope background in Double Chooz.

physics.ins-det↗

arXiv2014

Using L/E Oscillation Probability Distributions

This paper explores the use of $L/E$ oscillation probability distributions to compare experimental measurements and to evaluate oscillation models. In this case, $L$ is the distance of neutrino travel and $E$ is a measure of the interacting neutrino's energy. While comparisons using allowed and excluded regions for oscillation model parameters are likely the only rigorous method for these comparisons, the $L/E$ distributions are shown to give qualitative information on the agreement of an experiment's data with a simple two-neutrino oscillation model. In more detail, this paper also outlines how the $L/E$ distributions can be best calculated and used for model comparisons. Specifically, the paper presents the $L/E$ data points for the final MiniBooNE data samples and, in the Appendix, explains and corrects the mistaken analysis published by the ICARUS collaboration.

hep-ex↗

arXiv2014

Testing of High Voltage Surge Protection Devices for Use in Liquid Argon TPC Detectors

In this paper we demonstrate the capability of high voltage varistors and gas discharge tube arrestors for use as surge protection devices in liquid argon time projection chamber detectors. The insulating and clamping behavior of each type of device is characterized in air (room temperature), and liquid argon (90~K), and their robustness under high voltage and high energy surges in cryogenic conditions is verified. The protection of vulnerable components in liquid argon during a 150 kV high voltage discharge is also demonstrated. Each device is tested for argon contamination and light emission effects, and both are constrained to levels where no significant impact upon liquid argon time projection chamber functionality is expected. Both devices investigated are shown to be suitable for HV surge protection applications in cryogenic detectors.

physics.ins-det↗

arXiv2014

Background-independent measurement of $θ_{13}$ in Double Chooz

The oscillation results published by the Double Chooz collaboration in 2011 and 2012 rely on background models substantiated by reactor-on data. In this analysis, we present a background-model-independent measurement of the mixing angle $θ_{13}$ by including 7.53 days of reactor-off data. A global fit of the observed neutrino rates for different reactor power conditions is performed, yielding a measurement of both $θ_{13}$ and the total background rate. The results on the mixing angle are improved significantly by including the reactor-off data in the fit, as it provides a direct measurement of the total background rate. This reactor rate modulation analysis considers antineutrino candidates with neutron captures on both Gd and H, whose combination yields $\sin^2(2θ_{13})=$ 0.102 $\pm$ 0.028(stat.) $\pm$ 0.033(syst.). The results presented in this study are fully consistent with the ones already published by Double Chooz, achieving a competitive precision. They provide, for the first time, a determination of $θ_{13}$ that does not depend on a background model.

hep-ex↗

arXiv2014

Benchmarking TPB-coated Light Guides for Liquid Argon TPC Light Detection Systems

Scintillation light from liquid argon is produced at 128 nm and thus must be shifted to visible wavelengths in light detection systems used for Liquid Argon Time Projection Chambers (LArTPCs). To date, designs have employed tetraphenyl butadiene (TPB) coatings on photomultiplier tubes (PMTs) or plates placed in front of the PMTs. Recently, a new approach using TPB-coated light guides was proposed. In this paper, we show that the response of lightguides coated with TPB in a UV Transmitting (UVT) acrylic matrix is very similar to that of a coating using a polystyrene (PS) matrix. We obtain a factor of three higher light yield than has been previously reported from lightguides. This paper provides information on the response of the lightguides so that these can be modeled in simulations for future LArTPCs. This paper also identifies areas of R&D for potential improvements in the lightguide response

physics.ins-det↗

arXiv2014

The Effects of Dissolved Methane upon Liquid Argon Scintillation Light

In this paper we report on measurements of the effects of dissolved methane upon argon scintillation light. We monitor the light yield from an alpha source held 20 cm from a cryogenic photomultiplier tube (PMT) assembly as methane is injected into a high-purity liquid argon volume. We observe significant suppression of the scintillation light yield by dissolved methane at the 10 part per billion (ppb) level. By examining the late scintillation light time constant, we determine that this loss is caused by an absorption process and also see some evidence of methane-induced scintillation quenching at higher concentrations (50-100 ppb). Using a second PMT assembly we look for visible re-emission features from the dissolved methane which have been reported in gas-phase argon methane mixtures, and we find no evidence of visible re-emission from liquid-phase argon methane mixtures at concentrations between 10 ppb and 0.1%.

physics.ins-det↗

arXiv2013

Electron Antineutrino Disappearance at KamLAND and JUNO as Decisive Tests of the Short Baseline Anti-nu_mu to Anti-nu_e Appearance Anomaly

The IsoDAR antineutrino source, which produces a flux from 8Li isotope decay at rest, when paired with the proposed JUNO (Jiangmen Underground Neutrino Observatory) detector, has unprecedented sensitivity to anti-nu_e disappearance for oscillations at high Delta m^2. Assuming CPT invariance, the sensitive region for anti-nu_e disappearance can be used to restrict the allowed parameter space of an anti-nu_mu to anti-nu_e appearance signal. The 5 sigma sensitivity of this experiment covers the entire anti-nu_mu to anti-nu_e allowed parameter space from a combined fit to short-baseline experiments. This represents a decisive test of the LSND and MiniBooNE antineutrino appearance signals within all models that are $CPT$ invariant. Running IsoDAR at KamLAND restricts a large part of the appearance signal region in a similar way.

hep-ex↗

arXiv2013

Search for neutrino-antineutrino oscillations with a reactor experiment

The disappearance of reactor antineutrinos in the Double Chooz experiment is used to investigate the possibility of neutrino-antineutrino oscillations arising due to the breakdown of Lorentz invariance. We find no evidence for this phenomenon and set the first limits on 15 coefficients describing neutrino-antineutrino mixing within the framework of the Standard-Model Extension.

hep-ex↗

arXiv2013

Neutrino Experiments and the LHC: Friends Across 14 Orders of Magnitude

This proceeding explores some of the questions that connect the LHC and neutrino experiments: What is the origin of mass? What is the meaning of flavor? Is there direct evidence of new forces or particles? The neutrino program investigating these questions is large and diverse. The strategy here, to narrow the discussion, is to focus on relatively new ideas for experiments that may be less known within the LHC community.

hep-ex↗

arXiv2013

Precision $\bar ν_e$-electron Scattering Measurements with IsoDAR to Search for New Physics

IsoDAR provides a pure and intense $\bar ν_e$ source with an average energy of 6.5 MeV produced through $^8$Li $β$-decay. This source can be paired with a large scintillator detector, such as KamLAND, to produce a sample of $\bar ν_e$-electron scatters that is more than five times larger than what has been collected before. Such a sample would allow for a 3.2% measurement of $\sin^2θ_W$ and a sensitive search for non-standard interactions.

hep-ex↗

arXiv2013

Measurement of the Antineutrino Neutral-Current Elastic Differential Cross Section

We report the measurement of the flux-averaged antineutrino neutral current elastic scattering cross section ($dσ_{\bar νN \rightarrow \bar νN}/dQ^{2}$) on CH$_{2}$ by the MiniBooNE experiment using the largest sample of antineutrino neutral current elastic candidate events ever collected. The ratio of the antineutrino to neutrino neutral current elastic scattering cross sections and a ratio of antineutrino neutral current elastic to antineutrino charged current quasi elastic cross section is also presented.

hep-ex↗

arXiv2013

First Measurement of θ_13 from Delayed Neutron Capture on Hydrogen in the Double Chooz Experiment

The Double Chooz experiment has determined the value of the neutrino oscillation parameter $θ_{13}$ from an analysis of inverse beta decay interactions with neutron capture on hydrogen. This analysis uses a three times larger fiducial volume than the standard Double Chooz assessment, which is restricted to a region doped with gadolinium (Gd), yielding an exposure of 113.1 GW-ton-years. The data sample used in this analysis is distinct from that of the Gd analysis, and the systematic uncertainties are also largely independent, with some exceptions, such as the reactor neutrino flux prediction. A combined rate- and energy-dependent fit finds $\sin^2 2θ_{13}=0.097\pm 0.034(stat.) \pm 0.034 (syst.)$, excluding the no-oscillation hypothesis at 2.0 σ. This result is consistent with previous measurements of $\sin^2 2θ_{13}$.

hep-ex↗

arXiv2013

A Measurement of the Absorption of Liquid Argon Scintillation Light by Dissolved Nitrogen at the Part-Per-Million Level

We report on a measurement of the absorption length of scintillation light in liquid argon due to dissolved nitrogen at the part-per-million (ppm) level. We inject controlled quantities of nitrogen into a high purity volume of liquid argon and monitor the light yield from an alpha source. The source is placed at different distances from a cryogenic photomultiplier tube assembly. By comparing the light yield from each position we extract the absorption cross section of nitrogen. We find that nitrogen absorbs argon scintillation light with strength of $(1.51\pm 0.15)\times10^{-4} \;\mathrm{cm^{-1} ppm^{-1}}$, corresponding to an absorption cross section of $(7.14 \pm 0.74)\times10^{-21}\;\mathrm{cm^{2} molecule^{-1}}$. We obtain the relationship between absorption length and nitrogen concentration over the 0 to 50 ppm range and discuss the implications for the design and data analysis of future large liquid argon time projection chamber (LArTPC) detectors. Our results indicate that for a current-generation LArTPC, where a concentration of 2 parts per million of nitrogen is expected, the attenuation length due to nitrogen will be $30 \pm 3$ meters.

physics.ins-det↗

arXiv2013

First Measurement of the Muon Anti-Neutrino Double-Differential Charged Current Quasi-Elastic Cross Section

The largest sample ever recorded of $\numub$ charged-current quasi-elastic (CCQE, $\numub + p \to \mup + n$) candidate events is used to produce the minimally model-dependent, flux-integrated double-differential cross section $\frac{d^{2}σ}{dT_μd\uz}$ for $\numub$ incident on mineral oil. This measurement exploits the unprecedented statistics of the MiniBooNE anti-neutrino mode sample and provides the most complete information of this process to date. Also given to facilitate historical comparisons are the flux-unfolded total cross section $σ(E_ν)$ and single-differential cross section $\frac{dσ}{d\qsq}$ on both mineral oil and on carbon by subtracting the $\numub$ CCQE events on hydrogen. The observed cross section is somewhat higher than the predicted cross section from a model assuming independently-acting nucleons in carbon with canonical form factor values. The shape of the data are also discrepant with this model. These results have implications for intra-nuclear processes and can help constrain signal and background processes for future neutrino oscillation measurements.

hep-ex↗

arXiv2013

Cyclotrons as Drivers for Precision Neutrino Measurements

As we enter the age of precision measurement in neutrino physics, improved flux sources are required. These must have a well-defined flavor content with energies in ranges where backgrounds are low and cross section knowledge is high. Very few sources of neutrinos can meet these requirements. However, pion/muon and isotope decay-at-rest sources qualify. The ideal drivers for decay-at-rest sources are cyclotron accelerators, which are compact and relatively inexpensive. This paper describes a scheme to produce decay-at-rest sources driven by such cyclotrons, developed within the DAEdALUS program. Examples of the value of the high precision beams for pursuing Beyond Standard Model interactions are reviewed. New results on a combined DAEdALUS--Hyper-K search for CP-violation that achieve errors on the mixing matrix parameter of 4 degrees to 12 degrees are presented.

physics.acc-ph↗

arXiv2013

Whitepaper on the DAEdALUS Program

This whitepaper describes the status of the DAEdALUS program for development of high power cyclotrons as of the time of the final meeting of the Division of Particles and Fields 2013 Community Study ("Snowmass"). We report several new results, including a measurement capability between 4 and 12 degrees on the CP violating parameter in the neutrino sector. Past results, including the capability of the IsoDAR high Dm^2 antielectron neutrino disappearance search, are reviewed. A discussion of the R&D successes, including construction of a beamline teststand, and future plans are provided. This text incorporates short whitepapers written for subgroups in the Intensity Frontier and Frontier Capabilities Working Groups that are available on the Snowmass website.

physics.acc-ph↗