arXiv subjects

A. Garcia

Publications and source records attributed to A. Garcia.

At least 55 records · Page 3Linked to original sources

arXiv2017

Measurement of $\barν_μ$ and $ν_μ$ charged current inclusive cross sections and their ratio with the T2K off-axis near detector

We report a measurement of cross section $σ(ν_μ+{\rm nucleus}\rightarrowμ^{-}+X)$ and the first measurements of the cross section $σ(\barν_μ+{\rm nucleus}\rightarrowμ^{+}+X)$ and their ratio $R(\frac{σ(\bar ν)}{σ(ν)})$ at (anti-)neutrino energies below 1.5 GeV. We determine the single momentum bin cross section measurements, averaged over the T2K $\barν/ν$-flux, for the detector target material (mainly Carbon, Oxygen, Hydrogen and Copper) with phase space restricted laboratory frame kinematics of $θ_μ<32^\circ$ and $p_μ>$500 MeV/c. The results are $σ(\barν)=\left( 0.900\pm0.029{\rm (stat.)}\pm0.088{\rm (syst.)}\right)\times10^{-39}$ and $σ(ν)=\left( 2.41\ \pm0.022{\rm{(stat.)}}\pm0.231{\rm (syst.)}\ \right)\times10^{-39}$ in units of cm$^{2}$/nucleon and $R\left(\frac{σ(\barν)}{σ(ν)}\right)= 0.373\pm0.012{\rm (stat.)}\pm0.015{\rm (syst.)}$.

hep-ex↗

arXiv2017

Search for Lorentz and CPT violation using sidereal time dependence of neutrino flavor transitions over a short baseline

A class of extensions of the Standard Model allows Lorentz and CPT violations, which can be identified by the observation of sidereal modulations in the neutrino interaction rate. A search for such modulations was performed using the T2K on-axis near detector. Two complementary methods were used in this study, both of which resulted in no evidence of a signal. Limits on associated Lorentz and CPT violating terms from the Standard Model Extension have been derived taking into account their correlations in this model for the first time. These results imply such symmetry violations are suppressed by a factor of more than $10^{20}$ at the GeV scale.

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arXiv2017

First combined analysis of neutrino and antineutrino oscillations at T2K

T2K reports its first results in the search for CP violation in neutrino oscillations using appearance and disappearance channels for neutrino- and antineutrino-mode beam. The data include all runs from Jan 2010 to May 2016 and comprise $7.482\times10^{20}$,protons on target in neutrino mode, which yielded in the far detector 32 e-like and 135 $μ$-like events, and $7.471\times10^{20}$,protons on target in antineutrino mode which yielded 4 e-like and 66 $μ$-like events. Reactor measurements of $\sin^{2}2θ_{13}$ have been used as an additional constraint. The one-dimensional confidence interval at 90% for $δ_{CP}$ spans the range ($-3.13$, $-0.39$) for normal mass ordering. The CP conservation hypothesis ($δ_{CP}=0,π$) is excluded at 90% C.L.

hep-ex↗

arXiv2016

First Measurement of the Muon Neutrino Charged Current Single Pion Production Cross Section on Water with the T2K Near Detector

The T2K off-axis near detector, ND280, is used to make the first differential cross section measurements of muon neutrino charged current single positive pion production on a water target at energies ${\sim}0.8$ GeV. The differential measurements are presented as a function of muon and pion kinematics, in the restricted phase-space defined by $p_{π^+}>200$MeV/c, $p_{μ^-}>200$MeV/c, $\cos θ_{π^+}>0.3$ and $\cos θ_{μ^-}>0.3$. The total flux integrated $ν_μ$ charged current single positive pion production cross section on water in the restricted phase-space is measured to be $\langleσ\rangle_ϕ=4.25\pm0.48 (\mathrm{stat})\pm1.56 (\mathrm{syst})\times10^{-40} \mathrm{cm}^{2}/\mathrm{nucleon}$. The total cross section is consistent with the NEUT prediction ($5.03\times10^{-40} \mathrm{cm}^{2}/\mathrm{nucleon}$) and 2$σ$ lower than the GENIE prediction ($7.68\times10^{-40} \mathrm{cm}^{2}/\mathrm{nucleon}$). The differential cross sections are in good agreement with the NEUT generator. The GENIE simulation reproduces well the shapes of the distributions, but over-estimates the overall cross section normalization.

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arXiv2016

Measurement of coherent $π^{+}$ production in low energy neutrino-Carbon scattering

We report the first measurement of the flux-averaged cross section for charged current coherent $π^{+}$ production on carbon for neutrino energies less than 1.5 GeV to a restricted final state phase space region in the T2K near detector, ND280. Comparisons are made with predictions from the Rein-Sehgal coherent production model and the model by Alvarez-Ruso {\it et al.}, the latter representing the first implementation of an instance of the new class of microscopic coherent models in a neutrino interaction Monte Carlo event generator. This results contradicts the null results reported by K2K and SciBooNE in a similar neutrino energy region.

hep-ex↗

arXiv2016

Proposal for an Extended Run of T2K to $20\times10^{21}$ POT

Recent measurements by the T2K neutrino oscillation experiment indicate that CP violation in neutrino mixing may be observed in the future by long-baseline neutrino oscillation experiments. We propose an extension to the currently approved T2K running from $7.8\times 10^{21}~\mbox{POT}$ to $20\times 10^{21}~\mbox{POT}$, aiming at initial observation of CP violation with 3$\,σ$ or higher significance for the case of maximum CP violation. The program also contains a measurement of mixing parameters, $θ_{23}$ and $Δm^2_{32}$, with a precision of 1.7$^\circ$ or better and 1%, respectively. With accelerator and beamline upgrades, as well as analysis improvements, this program would occur before the next generation of long-baseline neutrino oscillation experiments that are expected to start operation in 2026.

hep-ex↗

arXiv2016

Sensitivity of the T2K accelerator-based neutrino experiment with an Extended run to $20\times10^{21}$ POT

Recent measurements at the T2K experiment indicate that CP violation in neutrino mixing may be observed in the future by long-baseline neutrino oscillation experiments. We explore the physics program of an extension to the currently approved T2K running of $7.8\times 10^{21}$ protons-on-target to $20\times 10^{21}$ protons-on-target,aiming at initial observation of CP violation with 3$\,σ$ or higher significance for the case of maximum CP violation. With accelerator and beam line upgrades, as well as analysis improvements, this program would occur before the next generation of long-baseline neutrino oscillation experiments that are expected to start operation in 2026.

hep-ex↗

arXiv2016

Measurement of Muon Antineutrino Oscillations with an Accelerator-Produced Off-Axis Beam

T2K reports its first measurements of the parameters governing the disappearance of $\barν_μ$ in an off-axis beam due to flavor change induced by neutrino oscillations. The quasimonochromatic $\barν_μ$ beam, produced with a peak energy of 0.6 GeV at J-PARC, is observed at the far detector Super-Kamiokande, 295 km away, where the $\barν_μ$ survival probability is expected to be minimal. Using a dataset corresponding to $4.01 \times 10^{20}$ protons on target, $34$ fully contained $μ$-like events were observed. The best-fit oscillation parameters are $\sin^2 (\barθ_{23}) = 0.45$ and $|Δ\bar{m}^2_{32}| = 2.51 \times 10^{-3}$ eV$^2$ with 68% confidence intervals of 0.38 - 0.64 and 2.26 - 2.80 $\times 10^{-3}$ eV$^2$ respectively. These results are in agreement with existing antineutrino parameter measurements and also with the $ν_μ$ disappearance parameters measured by T2K.

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arXiv2016

Measurement of double-differential muon neutrino charged-current interactions on C$_8$H$_8$ without pions in the final state using the T2K off-axis beam

We report the measurement of muon neutrino charged-current interactions on carbon without pions in the final state at the T2K beam energy using 5.734$\times10^{20}$ protons on target. For the first time the measurement is reported as a flux-integrated, double-differential cross-section in muon kinematic variables ($\cosθ_μ$, $p_μ$), without correcting for events where a pion is produced and then absorbed by final state interactions. Two analyses are performed with different selections, background evaluations and cross-section extraction methods to demonstrate the robustness of the results against biases due to model-dependent assumptions. The measurements compare favorably with recent models which include nucleon-nucleon correlations but, given the present precision, the measurement does not solve the degeneracy between different models. The data also agree with Monte Carlo simulations which use effective parameters that are tuned to external data to describe the nuclear effects. The total cross-section in the full phase space is $σ= (0.417 \pm 0.047 \text{(syst)} \pm 0.005 \text{(stat)})\times 10^{-38} \text{cm}^2$ $\text{nucleon}^{-1}$ and the cross-section integrated in the region of phase space with largest efficiency and best signal-over-background ratio ($\cosθ_μ>0.6$ and $p_μ> 200$ MeV) is $σ= (0.202 \pm 0.0359 \text{(syst)} \pm 0.0026 \text{(stat)}) \times 10^{-38} \text{cm}^2$ $\text{nucleon}^{-1}$.

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arXiv2015

Measurement of the $ν_μ$ CCQE cross section on carbon with the ND280 detector at T2K

The Charged-Current Quasi-Elastic (CCQE) interaction, $ν_{l} + n \rightarrow l^{-} + p$, is the dominant CC process at $E_ν\sim 1$ GeV and contributes to the signal in accelerator-based long-baseline neutrino oscillation experiments operating at intermediate neutrino energies. This paper reports a measurement by the T2K experiment of the $ν_μ$ CCQE cross section on a carbon target with the off-axis detector based on the observed distribution of muon momentum ($p_μ$) and angle with respect to the incident neutrino beam ($θ_μ$). The flux-integrated CCQE cross section was measured to be $(0.83 \pm 0.12) \times 10^{-38}\textrm{ cm}^{2}$ in good agreement with NEUT MC value of ${0.88 \times 10^{-38}} \textrm{ cm}^{2}$. The energy dependence of the CCQE cross section is also reported. The axial mass, $M_A^{QE}$, of the dipole axial form factor was extracted assuming the Smith-Moniz CCQE model with a relativistic Fermi gas nuclear model. Using the absolute (shape-only) $p_μcosθ_μ$ distribution, the effective $M_A^{QE}$ parameter was measured to be ${1.26^{+0.21}_{-0.18} \textrm{ GeV}/c^{2}}$ (${1.43^{+0.28}_{-0.22} \textrm{ GeV}/c^{2}}$).

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arXiv2015

Measurement of the muon neutrino inclusive charged-current cross section in the energy range of 1-3 GeV with the T2K INGRID detector

We report a measurement of the $ν_μ$-nucleus inclusive charged current cross section (=$σ^{cc}$) on iron using data from exposed to the J-PARC neutrino beam. The detector consists of 14 modules in total, which are spread over a range of off-axis angles from 0$^\circ$ to 1.1$^\circ$. The variation in the neutrino energy spectrum as a function of the off-axis angle, combined with event topology information, is used to calculate this cross section as a function of neutrino energy. The cross section is measured to be $σ^{cc}(1.1\text{ GeV}) = 1.10 \pm 0.15$ $(10^{-38}\text{cm}^2/\text{nucleon})$, $σ^{cc}(2.0\text{ GeV}) = 2.07 \pm 0.27$ $(10^{-38}\text{cm}^2/\text{nucleon})$, and $σ^{cc}(3.3\text{ GeV}) = 2.29 \pm 0.45$ $(10^{-38}\text{cm}^2/\text{nucleon})$, at energies of 1.1, 2.0, and 3.3 GeV, respectively. These results are consistent with the cross section calculated by the neutrino interaction generators currently used by T2K. More importantly, the method described here opens up a new way to determine the energy dependence of neutrino-nucleus cross sections.

hep-ex↗

arXiv2015

Measurement of the $ν_μ$ charged current quasi-elastic cross-section on carbon with the T2K on-axis neutrino beam

We report a measurement of the $ν_μ$ charged current quasi-elastic cross-sections on carbon in the T2K on-axis neutrino beam. The measured charged current quasi-elastic cross-sections on carbon at mean neutrino energies of 1.94 GeV and 0.93 GeV are $(11.95\pm 0.19(stat.)_{-1.47}^{+1.82} (syst.))\times 10^{-39}\mathrm{cm}^2/\mathrm{neutron}$ and $(10.64\pm 0.37(stat.)_{-1.65}^{+2.03} (syst.))\times 10^{-39}\mathrm{cm}^2/\mathrm{neutron}$, respectively. These results agree well with the predictions of neutrino interaction models. In addition, we investigated the effects of the nuclear model and the multi-nucleon interaction.

hep-ex↗

arXiv2015

Measurement of the Electron Neutrino Charged-current Interaction Rate on Water with the T2K ND280 pi-zero Detector

This paper presents a measurement of the charged current interaction rate of the electron neutrino beam component of the beam above $1.5$~GeV using the large fiducial mass of the T2K $π^0$ detector. The predominant poriton of the $ν_e$ flux ($\sim$85 %) at these energies comes from kaon decays. The measured ratio of the observed beam interaction rate to the predicted rate in the detector with water targets filled is 0.89 $\pm$ 0.08 (stat.) $\pm$ 0.11 (sys.), and with the water targets emptied is 0.90 $\pm$ 0.09 (stat.) $\pm$ 0.13 (sys.). The ratio obtained for the interactions on water only from an event subtraction method is 0.87 $\pm$ 0.33 (stat.) $\pm$ 0.21 (sys.). This is the first measurement of the interaction rate of electron neutrinos on water, which is particularly of interest to experiments with water Cherenkov detectors.

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arXiv2015

Pulsar Observations Using the First Station of the Long Wavelength Array and the LWA Pulsar Data Archive

We present initial pulsar results from the first station of the Long Wavelength Array (LWA1) obtained during the commissioning period of LWA1 and early science results. We present detections of periodic emission from 44 previously known pulsars, including 3 millisecond pulsars (MSPs). The effects of the interstellar medium on pulsar emission are significantly enhanced at the low frequencies of the LWA1 band (10--88 MHz), making LWA1 a very sensitive instrument for characterizing changes in dispersion measures (DM) and other effects from the interstellar medium. Pulsars also often have significant evolution in their pulse profile at low frequency and a break in their spectral index. We report DM measurements for 44 pulsars, mean flux density measurements for 36 pulsars, and multi-frequency component spacing and widths for 15 pulsars with more than one profile component. For 27 pulsars, we report spectral index measurements within our frequency range. We also introduce the LWA1 Pulsar Data Archive, which stores reduced data products from LWA1 pulsar observations. Reduced data products for the observations presented here can be found on the archive. Reduced data products from future LWA1 pulsar observations will also be made available through the archive.

astro-ph.IM↗

arXiv2015

Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with 6.6E20 protons on target

We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence intervals for the two possible mass hierarchies: Normal Hierarchy: $\sin^2θ_{23}=0.514^{+0.055}_{-0.056}$ and $Δm^2_{32}=(2.51\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$ Inverted Hierarchy: $\sin^2θ_{23}=0.511\pm0.055$ and $Δm^2_{13}=(2.48\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$ The analysis accounts for multi-nucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region: $δ_{CP}=[0.15,0.83]π$ for normal hierarchy and $δ_{CP}=[-0.08,1.09]π$ for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes Factor of 2.2. The most probable values and 68% 1D credible intervals for the other oscillation parameters, when reactor data are included, are: $\sin^2θ_{23}=0.528^{+0.055}_{-0.038}$ and $|Δm^2_{32}|=(2.51\pm0.11)\times 10^{-3}$ eV$^2$/c$^4$.

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arXiv2015

Neutrino Oscillation Physics Potential of the T2K Experiment

The observation of the recent electron neutrino appearance in a muon neutrino beam and the high-precision measurement of the mixing angle $θ_{13}$ have led to a re-evaluation of the physics potential of the T2K long-baseline neutrino oscillation experiment. Sensitivities are explored for CP violation in neutrinos, non-maximal $\sin^22θ_{23}$, the octant of $θ_{23}$, and the mass hierarchy, in addition to the measurements of $δ_{CP}$, $\sin^2θ_{23}$, and $Δm^2_{32}$, for various combinations of $ν$-mode and $\barν$-mode data-taking. With an exposure of $7.8\times10^{21}$~protons-on-target, T2K can achieve 1-$σ$ resolution of 0.050(0.054) on $\sin^2θ_{23}$ and $0.040(0.045)\times10^{-3}~\rm{eV}^2$ on $Δm^2_{32}$ for 100\%(50\%) neutrino beam mode running assuming $\sin^2θ_{23}=0.5$ and $Δm^2_{32} = 2.4\times10^{-3}$ eV$^2$. T2K will have sensitivity to the CP-violating phase $δ_{\rm{CP}}$ at 90\% C.L. or better over a significant range. For example, if $\sin^22θ_{23}$ is maximal (i.e $θ_{23}$=$45^\circ$) the range is $-115^\circ<δ_{\rm{CP}}<-60^\circ$ for normal hierarchy and $+50^\circ<δ_{\rm{CP}}<+130^\circ$ for inverted hierarchy. When T2K data is combined with data from the NO$ν$A experiment, the region of oscillation parameter space where there is sensitivity to observe a non-zero $δ_{CP}$ is substantially increased compared to if each experiment is analyzed alone.

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arXiv2014

The Green Bank Northern Celestial Cap Pulsar Survey - I: Survey Description, Data Analysis, and Initial Results

We describe an ongoing search for pulsars and dispersed pulses of radio emission, such as those from rotating radio transients (RRATs) and fast radio bursts (FRBs), at 350 MHz using the Green Bank Telescope. With the Green Bank Ultimate Pulsar Processing Instrument, we record 100 MHz of bandwidth divided into 4,096 channels every 81.92 $μs$. This survey will cover the entire sky visible to the Green Bank Telescope ($δ> -40^\circ$, or 82% of the sky) and outside of the Galactic Plane will be sensitive enough to detect slow pulsars and low dispersion measure ($<$30 $\mathrm{pc\,cm^{-3}}$) millisecond pulsars (MSPs) with a 0.08 duty cycle down to 1.1 mJy. For pulsars with a spectral index of $-$1.6, we will be 2.5 times more sensitive than previous and ongoing surveys over much of our survey region. Here we describe the survey, the data analysis pipeline, initial discovery parameters for 62 pulsars, and timing solutions for 5 new pulsars. PSR J0214$+$5222 is an MSP in a long-period (512 days) orbit and has an optical counterpart identified in archival data. PSR J0636$+$5129 is an MSP in a very short-period (96 minutes) orbit with a very low mass companion (8 $M_\mathrm{J}$). PSR J0645$+$5158 is an isolated MSP with a timing residual RMS of 500 ns and has been added to pulsar timing array experiments. PSR J1434$+$7257 is an isolated, intermediate-period pulsar that has been partially recycled. PSR J1816$+$4510 is an eclipsing MSP in a short-period orbit (8.7 hours) and may have recently completed its spin-up phase.

astro-ph.HE↗

arXiv2013

The Gravitational Universe

The last century has seen enormous progress in our understanding of the Universe. We know the life cycles of stars, the structure of galaxies, the remnants of the big bang, and have a general understanding of how the Universe evolved. We have come remarkably far using electromagnetic radiation as our tool for observing the Universe. However, gravity is the engine behind many of the processes in the Universe, and much of its action is dark. Opening a gravitational window on the Universe will let us go further than any alternative. Gravity has its own messenger: Gravitational waves, ripples in the fabric of spacetime. They travel essentially undisturbed and let us peer deep into the formation of the first seed black holes, exploring redshifts as large as z ~ 20, prior to the epoch of cosmic re-ionisation. Exquisite and unprecedented measurements of black hole masses and spins will make it possible to trace the history of black holes across all stages of galaxy evolution, and at the same time constrain any deviation from the Kerr metric of General Relativity. eLISA will be the first ever mission to study the entire Universe with gravitational waves. eLISA is an all-sky monitor and will offer a wide view of a dynamic cosmos using gravitational waves as new and unique messengers to unveil The Gravitational Universe. It provides the closest ever view of the early processes at TeV energies, has guaranteed sources in the form of verification binaries in the Milky Way, and can probe the entire Universe, from its smallest scales around singularities and black holes, all the way to cosmological dimensions.

astro-ph.CO↗