25,821 research outputs found
Kinematics of Current Region Fragmentation in Semi-Inclusive Deeply Inelastic Scattering
Different kinematical regimes of semi-inclusive deeply inelastic scattering
(SIDIS) processes correspond to different underlying partonic pictures, and it
is important to understand the transition between them. This is particularly
the case when there is sensitivity to intrinsic transverse momentum, in which
case kinematical details can become especially important. We address the
question of how to identify the current fragmentation region --- the
kinematical regime where a factorization picture with fragmentation functions
is appropriate. We distinguish this from soft and target fragmentation regimes.
Our criteria are based on the kinematic regions used in derivations of
factorization theorems. We argue that, when hard scales are of order a few
GeVs, there is likely significant overlap between different rapidity regions
that are normally understood to be distinct. We thus comment on the need to
take this into account with more unified descriptions of SIDIS, which should
span all rapidities for the produced hadron. Finally, we propose general
criteria for estimating the proximity to the current region at large Q.Comment: 9 Pages, 5 figures; minor clarifications and corrections, version
appearing in Physics Letters
Chandra Observation of PSR B1823-13 and its Pulsar Wind Nebula
We report on an observation of the Vela-like pulsar B1823-13 and its
synchrotron nebula with Chandra.The pulsar's spectrum fits a power-law model
with a photon index Gamma_PSR=2.4 for the plausible hydrogen column density
n_H=10^{22} cm^{-2}, corresponding to the luminosity L_PSR=8*10^{31} ergs
s^{-1} in the 0.5-8 keV band, at a distance of 4 kpc. The pulsar radiation
likely includes magnetospheric and thermal components, but they cannot be
reliably separated because of the small number of counts detected and strong
interstellar absorption. The pulsar is surrounded by a compact, 25''x 10'',
pulsar wind nebula (PWN) elongated in the east-west direction, which includes a
brighter inner component, 7''x 3'', elongated in the northeast-southwest
direction. The slope of the compact PWN spectrum is Gamma_comp=1.3, and the
0.5-8 keV luminosity is L_comp~3*10^{32} ergs s^{-1}. The compact PWN is
surrounded by asymmetric diffuse emission (extended PWN) seen up to at least
2.4' south of the pulsar, with a softer spectrum (Gamma_ext=1.9), and the 0.5-8
keV luminosity L_ext~10^{33}-10^{34} ergs s^{-1}. We also measured the pulsar's
proper motion using archival VLA data: \mu_\alpha=23.0+/-2.5 mas yr^{-1},
\mu_\delta=-3.9+/-3.3 mas yr^{-1}, which corresponds to the transverse
velocity v_perp=440 km s^{-1}. The direction of the proper motion is
approximately parallel to the elongation of the compact PWN, but it is nearly
perpendicular to that of the extended PWN and to the direction towards the
center of the bright VHE gamma-ray source HESS J1825-137, which is likely
powered by PSR B1823-13.Comment: 13 pages, 8 figures and 3 tables; submitted to Ap
Mapping the Kinematical Regimes of Semi-Inclusive Deep Inelastic Scattering
We construct a language for identifying kinematical regions of transversely
differential semi-inclusive deep inelastic scattering cross sections with
particular underlying partonic pictures, especially in regions of moderate to
low where sensitivity to kinematical effects outside the usual very high
energy limit becomes non-trivial. The partonic pictures map to power law
expansions whose leading contributions ultimately lead to well-known QCD
factorization theorems. We propose methods for estimating the consistency of
any particular region of overall hadronic kinematics with the kinematics of a
given underlying partonic picture. The basic setup of kinematics of
semi-inclusive deep inelastic scattering is also reviewed in some detail.Comment: 37 pages, 11 Figure
One More Step Towards Well-Composedness of Cell Complexes over nD Pictures
An nD pure regular cell complex K is weakly well-composed
(wWC) if, for each vertex v of K, the set of n-cells incident to v is
face-connected. In previous work we proved that if an nD picture I is
digitally well composed (DWC) then the cubical complex Q(I) associated
to I is wWC. If I is not DWC, we proposed a combinatorial algorithm
to “locally repair” Q(I) obtaining an nD pure simplicial complex PS(I)
homotopy equivalent to Q(I) which is always wWC. In this paper we give
a combinatorial procedure to compute a simplicial complex PS(¯I) which
decomposes the complement space of |PS(I)| and prove that PS(¯I) is also
wWC. This paper means one more step on the way to our ultimate goal:
to prove that the nD repaired complex is continuously well-composed
(CWC), that is, the boundary of its continuous analog is an (n − 1)-
manifold.Ministerio de Economía y Competitividad MTM2015-67072-
ICD discrimination of SVT versus VT with 1:1 V-A conduction: A review of the literature
AbstractInappropriate ICD shocks are associated with increased mortality. They also impair patients' quality of life, increase hospitalizations, and raise health-care costs. Nearly 80% of inappropriate ICD shocks are caused by supraventricular tachycardia. Here we report the case of a patient who received a single-lead dual-chamber sensing ICD for primary prevention of sudden cardiac death and experienced inappropriate ICD shocks. V-A time, electrogram morphology, and response to antitachycardia pacing suggested atrioventricular nodal reentry tachycardia, which was confirmed in an electrophysiology study. Inspired by this case, we performed a literature review to discuss mechanisms for discrimination of supraventricular tachycardia with 1:1 A:V relationship from ventricular tachycardia with 1:1 retrograde conduction
Challenges With Large Transverse Momentum in Semi-Inclusive Deeply Inelastic Scattering
We survey the current phenomenological status of semi-inclusive deeply inelastic scattering at moderate hard scales and in the limit of very large transverse momentum. As the transverse momentum becomes comparable to or larger than the overall hard scale, the differential cross sections should be calculable with fixed order perturbative QCD (pQCD) methods, while small transverse momentum (transverse-momentum-dependent factorization) approximations should eventually break down. We find large disagreement between HERMES and COMPASS data and fixed order calculations done with modern parton densities, even in regions of kinematics where such calculations should be expected to be very accurate. Possible interpretations are suggested
Large Transverse Momentum in Semi-Inclusive Deeply Inelastic Scattering Beyond Lowest Order
Motivated by recently observed tension between O(α2s) calculations of very large transverse momentum dependence in both semi-inclusive deep inelastic scattering and Drell-Yan scattering, we repeat the details of the calculation through an O(α2s) transversely differential cross section. The results confirm earlier calculations, and provide further support to the observation that tension exists with current parton distribution and fragmentation functions
Anomaly detection in quasi-periodic energy consumption data series: a comparison of algorithms
The diffusion of domotics solutions and of smart appliances and meters enables the monitoring of energy consumption at a very fine level and the development of forecasting and diagnostic applications. Anomaly detection (AD) in energy consumption data streams helps identify data points or intervals in which the behavior of an appliance deviates from normality and may prevent energy losses and break downs. Many statistical and learning approaches have been applied to the task, but the need remains of comparing their performances with data sets of different characteristics. This paper focuses on anomaly detection on quasi-periodic energy consumption data series and contrasts 12 statistical and machine learning algorithms tested in 144 different configurations on 3 data sets containing the power consumption signals of fridges. The assessment also evaluates the impact of the length of the series used for training and of the size of the sliding window employed to detect the anomalies. The generalization ability of the top five methods is also evaluated by applying them to an appliance different from that used for training. The results show that classical machine learning methods (Isolation Forest, One-Class SVM and Local Outlier Factor) outperform the best neural methods (GRU/LSTM autoencoder and multistep methods) and generalize better when applied to detect the anomalies of an appliance different from the one used for training
Planet Consumption and Stellar Metallicity Enhancements
The evolution of a giant planet within the stellar envelope of a
main-sequence star is investigated as a possible mechanism for enhancing the
stellar metallicities of the parent stars of extrasolar planetary systems.
Three-dimensional hydrodynamical simulations of a planet subject to impacting
stellar matter indicate that the envelope of a Jupiter-like giant planet can be
completely stripped in the outer stellar convection zone of a solar-mass star.
In contrast, Jupiter-like and less massive Saturn-like giant planets are able
to survive through the base of the convection zone of a 1.22 solar-mass star.
Although strongly dependent on details of planetary interior models, partial or
total dissolution of giant planets can result in significant enhancements in
the metallicity of host stars with masses between about 1.0 and 1.3 solar
masses. The implications of these results with regard to planetary orbital
migration are briefly discussed.Comment: 11 pages, 2 figures, accepted for ApJ Letter
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