5,437 research outputs found
An algorithm for quantifying dependence in multivariate data sets
We describe an algorithm to quantify dependence in a multivariate data set.
The algorithm is able to identify any linear and non-linear dependence in the
data set by performing a hypothesis test for two variables being independent.
As a result we obtain a reliable measure of dependence.
In high energy physics understanding dependencies is especially important in
multidimensional maximum likelihood analyses. We therefore describe the problem
of a multidimensional maximum likelihood analysis applied on a multivariate
data set with variables that are dependent on each other. We review common
procedures used in high energy physics and show that general dependence is not
the same as linear correlation and discuss their limitations in practical
application.
Finally we present the tool CAT, which is able to perform all reviewed
methods in a fully automatic mode and creates an analysis report document with
numeric results and visual review.Comment: 4 pages, 3 figure
BSAURUS- A Package For Inclusive B-Reconstruction in DELPHI
BSAURUS is a software package for the inclusive reconstruction of B-hadrons
in Z-decay events taken by the DELPHI detector at LEP. The BSAURUS goal is to
reconstruct B-decays, by making use of as many properties of b-jets as
possible, with high efficiency and good purity. This is achieved by exploiting
the capabilities of the DELPHI detector to their extreme, applying wherever
possible physics knowledge about B production and decays and combining
different information sources with modern tools- mainly artificial neural
networks. This note provides a reference of how BSAURUS outputs are formed, how
to access them within the DELPHI framework, and the physics performance one can
expect.Comment: 52 pages, 24 figures, added author Z.
The first direct double neutron star merger detection: implications for cosmic nucleosynthesis
The astrophysical r-process site where about half of the elements heavier
than iron are produced has been a puzzle for several decades. Here we discuss
the role of neutron star mergers (NSMs) in the light of the first direct
detection of such an event in both gravitational (GW) and electromagnetic (EM)
waves. We analyse bolometric and NIR lightcurves of the first detected double
neutron star merger and compare them to nuclear reaction network-based
macronova models. The slope of the bolometric lightcurve is consistent with the
radioactive decay of neutron star ejecta with (but not
larger), which provides strong evidence for an r-process origin of the
electromagnetic emission. This rules out in particular "nickel winds" as major
source of the emission. We find that the NIR lightcurves can be well fitted
either with or without lanthanide-rich ejecta. Our limits on the ejecta mass
together with estimated rates directly confirm earlier purely theoretical or
indirect observational conclusions that double neutron star mergers are indeed
a major site of cosmic nucleosynthesis. If the ejecta mass was {\em typical},
NSMs can easily produce {\em all} of the estimated Galactic r-process matter,
and --depending on the real rate-- potentially even more. This could be a hint
that the event ejected a particularly large amount of mass, maybe due to a
substantial difference between the component masses. This would be compatible
with the mass limits obtained from the GW-observation. The recent observations
suggests that NSMs are responsible for a broad range of r-process nuclei and
that they are at least a major, but likely the dominant r-process site in the
Universe.Comment: 11 pages, 8 figures; accepted for A \&
MACRIB High efficiency - high purity hadron identification for DELPHI
Analysis of the data shows that hadron tags of the two standard DELPHI particle identification packages RIBMEAN and HADSIGN are weakly correlated. This led to the idea of constructing a neural network for both kaon and proton identification using as input the existing tags from RIBMEAN and HADSIGN, as well as preproccessed TPC and RICH detector measurements together with additional dE/dx information from the DELPHI vertex detector. It will be shown in this note that the net output is much more efficient at the same purity than the HADSIGN or RIBMEAN tags alone. We present an easy-to-use routine performing the necessary calculations
Detectability of kilonovae in optical surveys: post-mortem examination of the LVC O3 run follow-up
The detection of the binary neutron star (BNS) merger GW170817 and the associated electromagnetic (EM) counterpart, the 'kilonova' (kN) AT2017gfo, opened a new era in multimessenger astronomy. However, despite many efforts, it has been proven very difficult to find additional kNe, even though LIGO/Virgo has reported at least one BNS event during their latest run, O3. The focus of this work is the exploration of the sensitivity of the adopted optical surveys searching for kNe during O3. We propose ways to optimize the choices of filters and survey depth to boost the detection efficiency for these faint and fast-evolving transients in the future. In particular, we use kN models to explore the dependence on ejecta mass, geometry, viewing angle, wavelength coverage, and source distance. We find that the kN detection efficiency has a strong viewing-angle dependence, especially for filters blueward of i-band. This loss of sensitivity can be mitigated by early, deep, observations. Efficient gri counterpart searches for kNe at ∼200 Mpc would require reaching a limiting magnitude mlim = 23 mag, to ensure good sensitivity over a wide range of the model phase-space. We conclude that kN searches during O3 were generally too shallow to detect BNS optical counterparts, even under optimistic assumptions
Faddeev study of heavy baryon spectroscopy
We investigate the structure of heavy baryons containing a charm or a bottom
quark. We employ a constituent quark model successful in the description of the
baryon-baryon interaction which is consistent with the light baryon spectra. We
solve exactly the three-quark problem by means of the Faddeev method in
momentum space. Heavy baryon spectrum shows a manifest compromise between
perturbative and nonperturbative contributions. The flavor dependence of the
one-gluon exchange is analyzed. We assign quantum numbers to some already
observed resonances and we predict the first radial and orbital excitations of
all states with or 3/2. We combine our results with heavy quark
symmetry and lowest-order SU(3) symmetry breaking to predict the masses and
quantum numbers of six still non-measured ground-state beauty baryons.Comment: 22 pages, 4 figures, 8 tables. Accepted for publication in J. Phys.
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