2,133 research outputs found
Resolving Neutrino Mass Hierarchy and CP Degeneracy by Two Identical Detectors with Different Baselines
We explore the possibility of simultaneous determination of neutrino mass
hierarchy and the CP violating phase by using two identical detectors placed at
different baseline distances. We focus on a possible experimental setup using
neutrino beam from J-PARC facility in Japan with beam power of 4MW and megaton
(Mton)-class water Cherenkov detectors, one placed in Kamioka and the other at
somewhere in Korea. We demonstrate, under reasonable assumptions of systematic
uncertainties, that the two-detector complex with each fiducial volume of 0.27
Mton has potential of resolving neutrino mass hierarchy up to sin^2 2theta_{13}
> 0.03 (0.055) at 2\sigma (3\sigma) CL for any values of delta and at the same
time has the sensitivity to CP violation by 4 + 4 years running of nu_e and
nu_e-bar appearance measurement. The significantly enhanced sensitivity is due
to clean detection of modulation of neutrino energy spectrum, which is enabled
by cancellation of systematic uncertainties between two identical detectors
which receive the neutrino beam with the same energy spectrum in the absence of
oscillations.Comment: 23 pages, 10 figures, version published in PR
The Waveform Digitiser of the Double Chooz Experiment: Performance and Quantisation Effects on PhotoMultiplier Tube Signals
We present the waveform digitiser used in the Double Chooz experiment. We
describe the hardware and the custom-built firmware specifically developed for
the experiment. The performance of the device is tested with regards to
digitising low light level signals from photomultiplier tubes and measuring
pulse charge. This highlights the role of quantisation effects and leads to
some general recommendations on the design and use of waveform digitisers.Comment: 14 pages, 8 figures, accepted for publication in JINS
Optimal Testing Intervals in the Squatting Test to Determine Baroreflex Sensitivity
The recently introduced “squatting test” (ST) utilizes a simple postural change to perturb
the blood pressure and to assess baroreflex sensitivity (BRS). In our study, we estimated the
reproducibility of and the optimal testing interval between the STs in healthy volunteers.
Thirty-four subjects free of cardiovascular disorders and taking no medication were
instructed to perform the repeated ST at 30-sec, 1-min, and 3-min intervals in duplicate in a
random sequence, while the systolic blood pressure (SBP) and pulse intervals were measured.
Baroreflex sensitivity was estimated by plotting reflex increases and decreases in the SBP and
succeeding pulse intervals during stand-to-squat and squat-to-stand maneuvers, respectively.
Correlations between duplicate BRS data at each testing interval were analyzed by the
Pearson’s correlation coefficient, while agreements were assessed by Bland-Altman plots.
Two measurements of BRS during stand-to-squat and squat-to-stand maneuvers demonstrated
significant correlations at both 1-min and 3-min intervals, while at 30-sec intervals correlation
was poor. Correlation coefficients became considerably greater in each maneuver as the
measurement interval was increased from 30 sec to 3 min. Our results suggest that the testing
interval in the ST should be at least 1 min long, but ideally it should be longer than or equal
to 3 min, to assess the baroreflex adequately.У нещодавно запропонованому «тесті присідання» (ТП)
використовується проста зміна пози для індукції зрушення
кров’яного тиску, що дозволяє визначити барорефлекторну
чутливість (БРЧ). Ми оцінювали ступінь відтворюваності
та оптимальні інтервали між ТП, що реалізовувалися
здоровими випробуваними. Групу з 34 тестованих, які не
мали будь-яких серцево-судинних розладів та не приймали
якихось ліків, інструктували виконувати повторні подвійні
ТП у випадковій послідовності з інтервалами 30 с, 1 та 3 хв;
при цьому вимірювали систолічний кров’яний тиск (СКТ)
та кардіоінтервали. Рефлекторні підвищення та зниження
СКТ і послідовні кардіоінтервали під час рухів присідання
та повернення у вертикальну позу представляли графічно.
Залежність між повторними визначеннями БРЧ при
кожному інтервалі між тестами аналізували, встановлюючи
коефіцієнти кореляції Пірсона. Виміри БРЧ під час рухів
присідання та підйому демонстрували істотну кореляцію
при інтервалах 1 та 3 хв, а при інтервалах 30 с кореляція
була слабшою. Коефіцієнти кореляції ставали помітно
значнішими з кожним рухом і збільшенням інтервалів між
вимірами від 30 с до 3 хв. Наші результати вказують на те,
що адекватна оцінка барорефлексу може бути забезпечена
при інтервалах між ТП не менше 1 хв (бажано 3 хв або
більше)
Global analysis of neutrino masses, mixings and phases: entering the era of leptonic CP violation searches
We perform a global analysis of neutrino oscillation data, including
high-precision measurements of the neutrino mixing angle theta_13 at reactor
experiments, which have confirmed previous indications in favor of theta_13>0.
Recent data presented at the Neutrino 2012 Conference are also included. We
focus on the correlations between theta_13 and the mixing angle theta_23, as
well as between theta_13 and the neutrino CP-violation phase delta. We find
interesting indications for theta_23< pi/4 and possible hints for delta ~ pi,
with no significant difference between normal and inverted mass hierarchy.Comment: Updated version, including recent data released at the Neutrino 2012
Conference. Some references adde
The 3-D kinematics of water masers around the semiregular variable RT Virginis
We report observations of water masers around the semiregular variable RT
Virginis (RT Vir), which have been made with the Very Long Baseline Array
(VLBA) of the National Radio Astronomy Observatory (NRAO) at five epochs, each
separated by three weeks of time. We detected about 60 maser features at each
epoch. Overall, 61 features, detected at least twice, were tracked by their
radial velocities and proper motions. The 3-D maser kinematics exhibited a
circumstellar envelope that is expanding roughly spherically with a velocity of
about 8 km/s. Asymmetries in both the spatial and velocity distributions of the
maser features were found in the envelope, but less significant than that found
in other semiregular variables. Systematic radial-velocity drifts of individual
maser features were found with amplitudes of <= 2 km/s/yr. For one maser
feature, we found a quadratic position shift with time along a straight line on
the sky. This apparent motion indicates an acceleration with an amplitude of 33
km/s/yr, implying the passage of a shock wave driven by the stellar pulsation
of RT Vir. The acceleration motion is likely seen only on the sky plane because
of a large velocity gradient formed in the accelerating maser region. We
estimated the distance to RT Vir to be about 220 pc on the basis of both the
statistical parallax and model-fitting methods for the maser kinematics.Comment: 18 pages, 8 figures. Accepted to appear in the Astrophysical Journa
Measurement of the mechanical loss of a cooled reflective coating for gravitational wave detection
We have measured the mechanical loss of a dielectric multilayer reflective
coating (ion-beam sputtered SiO and TaO) in cooled mirrors. The
loss was nearly independent of the temperature (4 K 300 K), frequency,
optical loss, and stress caused by the coating, and the details of the
manufacturing processes. The loss angle was . The
temperature independence of this loss implies that the amplitude of the coating
thermal noise, which is a severe limit in any precise measurement, is
proportional to the square root of the temperature. Sapphire mirrors at 20 K
satisfy the requirement concerning the thermal noise of even future
interferometric gravitational wave detector projects on the ground, for
example, LCGT.Comment: 8 pages, 6 figures, 3 tables : accepted version (by Physical Review
D
- …