195 research outputs found
Proton structure corrections to electronic and muonic hydrogen hyperfine splitting
We present a precise determination of the polarizability and other proton
structure dependent contributions to the hydrogen hyperfine splitting, based
heavily on the most recent published data on proton spin dependent structure
functions from the EG1 experiment at the Jefferson Laboratory. As a result, the
total calculated hyperfine splitting now has a standard deviation slightly
under 1 part-per-million, and is about 1 standard deviation away from the
measured value. We also present results for muonic hydrogen hyperfine
splitting, taking care to ensure the compatibility of the recoil and
polarizability terms.Comment: 9 pages, 1 figur
To verify four 5-year-old mathematical models to predict the outcome of ICU patients
The aim of this study is to verify calibration and discrimination after 5 years in the case mix of patients admitted to the Intensive Care Unit (ICU) during the year 2000. In this way we want to perform a quality control of our ICU in order to justify the increased amount of money spent for intensive care.A prospective study has been made on the 357 patients admitted to the ICU during the year 2000. The Apache II score was calculated within the first 24 hours and, depending on the length of stay in the ICU, on the 5(th), 10(th) and 15(th) day after ICU admission. On the basis of the 4 mathematical models death risk has been calculated for each of the 4 times. The Hosmer-Lemeshow test was performed for calibration and ROC curves for discrimination, always for each of the 4 mathematical models.The 1(st) model, at 24 hours from ICU admission, showed a bad calibration (p=0.000088), while the ROC curve was 0.744+/-0.32. Also the 2(nd) model, at the 5(th) day from admission, showed a bad calibration (p=0.000588), with ROC curve of 0.827+/-0.04. The 3(rd) model (10(th) day), was well calibrated (p=0.112247) and discriminating (ROC=0.888 +/-0.04). Finally the models at 15 days showed again a bad calibration (p=0.001422) but a very good discrimination (area=0.906+/-0.06).Developing mathematical models to predict mortality within ICUs can be useful to assess quality of care, even if these models should not be the only ICU quality controls, but must be accompanied by other indicators, looking at quality of life of the patients after ICU discharge
Muonic hydrogen cascade time and lifetime of the short-lived state
Metastable muonic-hydrogen atoms undergo collisional -quenching,
with rates which depend strongly on whether the kinetic energy is above
or below the energy threshold. Above threshold, collisional
excitation followed by fast radiative
deexcitation is allowed. The corresponding short-lived component
was measured at 0.6 hPa room temperature gas pressure, with
lifetime ns (i.e.,
at liquid-hydrogen density) and population
% (per atom). In
addition, a value of the cascade time, ns, was found.Comment: 4 pages, 3 figure
muCool: A novel low-energy muon beam for future precision experiments
Experiments with muons () and muonium atoms () offer
several promising possibilities for testing fundamental symmetries. Examples of
such experiments include search for muon electric dipole moment, measurement of
muon and experiments with muonium from laser spectroscopy to gravity
experiments. These experiments require high quality muon beams with small
transverse size and high intensity at low energy.
At the Paul Scherrer Institute, Switzerland, we are developing a novel device
that reduces the phase space of a standard beam by a factor of
with efficiency. The phase space compression is achieved by
stopping a standard beam in a cryogenic helium gas. The stopped
are manipulated into a small spot with complex electric and magnetic
fields in combination with gas density gradients. From here, the muons are
extracted into the vacuum and into a field-free region. Various aspects of this
compression scheme have been demonstrated. In this article the current status
will be reported.Comment: 8 pages, 5 figures, TCP 2018 conference proceeding
Improved X-ray detection and particle identification with avalanche photodiodes
Avalanche photodiodes are commonly used as detectors for low energy x-rays.
In this work we report on a fitting technique used to account for different
detector responses resulting from photo absorption in the various APD layers.
The use of this technique results in an improvement of the energy resolution at
8.2 keV by up to a factor of 2, and corrects the timing information by up to 25
ns to account for space dependent electron drift time. In addition, this
waveform analysis is used for particle identification, e.g. to distinguish
between x-rays and MeV electrons in our experiment.Comment: 6 pages, 6 figure
The proton radius puzzle
High-precision measurements of the proton radius from laser spectroscopy of
muonic hydrogen demonstrated up to six standard deviations smaller values than
obtained from electron-proton scattering and hydrogen spectroscopy. The status
of this discrepancy, which is known as the proton radius puzzle will be
discussed in this paper, complemented with the new insights obtained from
spectroscopy of muonic deuterium.Comment: Moriond 2017 conference, 8 pages, 4 figure
Muon Physics: A Pillar of the Standard Model
Since its discovery in the 1930s, the muon has played an important role in
our quest to understand the sub-atomic theory of matter. The muon was the first
second-generation standard-model particle to be discovered, and its decay has
provided information on the (Vector -Axial Vector) structure of the weak
interaction, the strength of the weak interaction, G_F, and the conservation of
lepton number (flavor) in muon decay. The muon's anomalous magnetic moment has
played an important role in restricting theories of physics beyond the standard
standard model, where at present there is a 3.4 standard-deviation difference
between the experiment and standard-model theory. Its capture on the atomic
nucleus has provided valuable information on the modification of the weak
current by the strong interaction which is complementary to that obtained from
nuclear beta decay.Comment: 8 pages, 9 figures. Invited paper for the Journal of Physical Society
in Japan (JPSJ), Special Topics Issue "Frontiers of Elementary Particle
Physics, The Standard Model and beyond
Characterization of large area avalanche photodiodes in X-ray and VUV-light detection
The present manuscript reviews our R+D studies on the application of large area avalanche photodiodes (LAAPDs) to the detection of X-rays and vacuum ultraviolet (VUV) light. The operational characteristics of LAAPDs manufactured by Advanced Photonix Inc. were investigated for X-ray detection at room temperature. The optimum energy resolution obtained in four LAAPDs investigated was found to be in the range 10-18% for 5.9 keV X-rays. The observed variations are associated with dark current differences between the several prototypes. LAAPDs have demonstrated high counting rate capability (up to about 10â”/s) and applicability in diverse areas, mainly low-energy X-ray detection, where LAAPDs selected for low dark current may achieve better performance than proportional counters. LAAPDs were also investigated as VUV photosensors, presenting advantages compared to photomultiplier tubes. X-rays are often used as a reference in light measurements; this may be compromised by the non-linearity between gains measured for X-rays and VUV-light. The gain was found to be lower for X-rays than for VUV light, especially at higher bias voltages. For 5.9 keV X-rays, gain variations of 10% and 6% were measured relative to VUV light produced in argon ( ⌠128 nm) and xenon ( ⌠172 nm) for gains of about 200. The effect of temperature on the LAAPD performance was investigated for X-ray and VUV-light detection. Gain variations of more than -4% per oC were measured for 5.9 keV X-rays for gains above 200, while for VUV light variations are larger than -5% per oC. The energy resolution was found to improve with decreasing temperature, what is mainly attributed to dark current. The excess noise factor, another contribution to the energy resolution, was experimentally determined and found to be independent of temperature, increasing linearly with gain, from 1.8 to 2.3 for a 50-300 gain range. The LAAPD response under intense magnetic fields up to 5 Tesla was investigated. While for X-ray detection the APD response practically does not vary with the magnetic field, for 172 nm VUV light a significant amplitude reduction of more than 20% was observed
Characterization of large area avalanche photodiodes in X-ray and VUV-light detection
The present manuscript summarizes novel studies on the application of large
area avalanche photodiodes (LAAPDs) to the detection of X-rays and vacuum
ultraviolet (VUV) light. The operational characteristics of four different
LAAPDs manufactured by Advanced Photonix Inc., with active areas of 80 and 200
mm^2 were investigated for X-ray detection at room temperature. The best energy
resolution was found to be in the 10-18% range for 5.9 keV X-rays. The LAAPD,
being compact, simple to operate and with high counting rate capability (up to
about 10^5/s), proved to be useful in several applications, such as low-energy
X-ray detection, where they can reach better performance than proportional
counters. Since X-rays are used as reference in light measurements, the gain
non-linearity between 5.9 keV X-rays and light pulses was investigated. The
gain ratio between X-rays and VUV light decreases with gain, reaching 10 and 6%
variations for VUV light produced in argon (~128 nm) and xenon (~172 nm),
respectively, for a gain 200, while for visible light (~635 nm) the variation
is lower than 1%. The effect of temperature on the LAAPD performance was
investigated. Relative gain variations of about -5% per Celsius degree were
observed for the highest gains. The excess noise factor was found to be
independent on temperature, being between 1.8 and 2.3 for gains from 50 to 300.
The energy resolution is better for decreasing temperatures due mainly to the
dark current. LAAPDs were tested under intense magnetic fields up to 5 T, being
insensitive when used in X-ray and visible-light detection, while for VUV light
a significant amplitude reduction was observed at 5 T.Comment: 25 pages, 40 figures, submitted to JINS
Characterization of large area avalanche photodiodes in X-ray and VUV-light detection
The present manuscript summarizes novel studies on the application of large
area avalanche photodiodes (LAAPDs) to the detection of X-rays and vacuum
ultraviolet (VUV) light. The operational characteristics of four different
LAAPDs manufactured by Advanced Photonix Inc., with active areas of 80 and 200
mm^2 were investigated for X-ray detection at room temperature. The best energy
resolution was found to be in the 10-18% range for 5.9 keV X-rays. The LAAPD,
being compact, simple to operate and with high counting rate capability (up to
about 10^5/s), proved to be useful in several applications, such as low-energy
X-ray detection, where they can reach better performance than proportional
counters. Since X-rays are used as reference in light measurements, the gain
non-linearity between 5.9 keV X-rays and light pulses was investigated. The
gain ratio between X-rays and VUV light decreases with gain, reaching 10 and 6%
variations for VUV light produced in argon (~128 nm) and xenon (~172 nm),
respectively, for a gain 200, while for visible light (~635 nm) the variation
is lower than 1%. The effect of temperature on the LAAPD performance was
investigated. Relative gain variations of about -5% per Celsius degree were
observed for the highest gains. The excess noise factor was found to be
independent on temperature, being between 1.8 and 2.3 for gains from 50 to 300.
The energy resolution is better for decreasing temperatures due mainly to the
dark current. LAAPDs were tested under intense magnetic fields up to 5 T, being
insensitive when used in X-ray and visible-light detection, while for VUV light
a significant amplitude reduction was observed at 5 T.Comment: 25 pages, 40 figures, submitted to JINS
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