1,775 research outputs found

### Running of Low-Energy Neutrino Masses, Mixing Angles and CP Violation

We calculate the running of low-energy neutrino parameters from the bottom
up, parameterizing the unknown seesaw parameters in terms of the dominance
matrix $R$. We find significant running only if the $R$ matrix is non-trivial
and the light-neutrino masses are moderately degenerate. If the light-neutrino
masses are very hierarchical, the quark-lepton complementarity relation
$\theta_c + \theta_{12} = \pi/4$ is quite stable, but $\theta_{13,23}$ may run
beyond their likely future experimental errors. The running of the oscillation
phase $\delta$ is enhanced by the smallness of $\theta_{13}$, and jumps in the
mixing angles occur in cases where the light-neutrino mass eigenstates cross.Comment: 14 pages, 7 figure

### Implications of XENON100 and LHC results for Dark Matter models

We perform a fit to the recent Xenon100 data and study its implications for
Dark Matter scenarios. We find that Inelastic Dark Matter is disfavoured as an
explana- tion to the DAMA/LIBRA annual modulation signal. Concerning the scalar
singlet DM model, we find that the Xenon100 data disfavors its constrained
limit. We study the CMSSM as well as the low scale phenomenological MSSM taking
into account latest Tevatron and LHC data (1.1/fb) about sparticles and Bs
\rightarrow {\mu}{\mu}. After the EPS 2011 conference, LHC excludes the
"Higgs-resonance" region of DM freeze-out and Xenon100 disfavors the
"well-tempered" bino/higgsino, realized in the "focus-point" region of the
CMSSM parameter space. The preferred region shifts to heavier sparticles,
higher fine-tuning, higher tan {\beta} and the quality of the fit deteriorates.Comment: v4: addendum included at the light of the Dark Matter and Higgs data
presented during july 2012 by the Xenon100, ATLAS and CMS collaboration

### Matter parity as the origin of scalar Dark Matter

We extend the concept of matter parity $P_M=(-1)^{3(B-L)}$ to
non-supersymmetric theories and argue that $P_M$ is the natural explanation to
the existence of Dark Matter of the Universe. We show that the
non-supersymmetric Dark Matter must be contained in scalar 16 representation(s)
of $SO(10),$ thus the unique low energy Dark Matter candidates are $P_M$-odd
complex scalar singlet(s) $S$ and inert scalar doublet(s) $H_2.$ We have
calculated the thermal relic Dark Matter abundance of the model and shown that
its minimal form may be testable at LHC via the SM Higgs boson decays $H_1\to
DM DM.$ The PAMELA anomaly can be explained with the decays $DM\to \nu l W$
induced via seesaw-like operator which is additionally suppressed by Planck
scale. Because the SM fermions are odd under matter parity too, the DM sector
is just our scalar relative.Comment: The origin of scalar DM is emphasized, version accepted by PR

### Evolutionary algorithms for hyperparameter optimization in machine learning for application in high energy physics

The analysis of vast amounts of data constitutes a major challenge in modern
high energy physics experiments. Machine learning (ML) methods, typically
trained on simulated data, are often employed to facilitate this task. Several
choices need to be made by the user when training the ML algorithm. In addition
to deciding which ML algorithm to use and choosing suitable observables as
inputs, users typically need to choose among a plethora of algorithm-specific
parameters. We refer to parameters that need to be chosen by the user as
hyperparameters. These are to be distinguished from parameters that the ML
algorithm learns autonomously during the training, without intervention by the
user. The choice of hyperparameters is conventionally done manually by the user
and often has a significant impact on the performance of the ML algorithm. In
this paper, we explore two evolutionary algorithms: particle swarm optimization
(PSO) and genetic algorithm (GA), for the purposes of performing the choice of
optimal hyperparameter values in an autonomous manner. Both of these algorithms
will be tested on different datasets and compared to alternative methods.Comment: Corrected typos. Removed a remark on page 2 regarding the similarity
of minimization and maximization problem. Removed a remark on page 9
(Summary) regarding thee ANN, since this was not studied in the pape

### Dark Matter as the signal of Grand Unification

We argue that the existence of Dark Matter (DM) is a possible consequence of
GUT symmetry breaking. In GUTs like SO(10), discrete Z_2 matter parity
(-1)^{3(B-L)} survives despite of broken B-L, and group theory uniquely
determines that the only possible Z_2-odd matter multiplets belong to
representation 16. We construct the minimal non-SUSY SO(10) model containing
one scalar 16 for DM and study its predictions below M_{G}. We find that EWSB
occurs radiatively due to DM couplings to the SM Higgs boson. For thermal relic
DM the mass range M_{DM}\sim (0.1-1) TeV is predicted by model perturbativity
up to M_{G}. For M_{DM}\sim (1) TeV to explain the observed cosmic ray
anomalies with DM decays, there exists a lower bound on the spin-independent
direct detection cross section within the reach of planned experiments.Comment: DM direct detection cross section is corrected by adding s-quark
contribution which turned out to be the dominant one. The prediction is just
below the present CDMS and XENON10 bound. Extended version, RGE-s included,
new references adde

### Direct detection and CMB constraints on light DM scenario of top quark asymmetry and dijet excess at Tevatron

We study in detail the model by Isidori and Kamenik that is claimed to
explain the top quark forward-backward asymmetry at Tevatron, provide GeV-scale
dark matter (DM), and possibly improve the agreement between data and theory in
Tevatron W+jj events. We compute the DM thermal relic density, the
spin-independent DM-nucleon scattering cross section, and the cosmic microwave
background constraints on both Dirac and Majorana neutralino DM in the
parameter space that explains the top asymmetry. A stable light neutralino is
not allowed unless the local DM density is 3-4 times smaller than expected, in
which case Dirac DM with mass around 3 GeV may be possible, to be tested by the
Planck mission. The model predicts a too broad excess in the dijet distribution
and a strong modification of the missing E_T distribution in W+jj events.Comment: 4 pages, 4 figures; fig. 2 corrected, conclusions slightly changed,
matches published versio

### Implications of the 125 GeV Higgs boson for scalar dark matter and for the CMSSM phenomenology

We study phenomenological implications of the ATLAS and CMS hint of a $125\pm
1$ GeV Higgs boson for the singlet, and singlet plus doublet non-supersymmetric
dark matter models, and for the phenomenology of the CMSSM. We show that in
scalar dark matter models the vacuum stability bound on Higgs boson mass is
lower than in the standard model and the 125 GeV Higgs boson is consistent with
the models being valid up the GUT or Planck scale. We perform a detailed study
of the full CMSSM parameter space keeping the Higgs boson mass fixed to $125\pm
1$ GeV, and study in detail the freeze-out processes that imply the observed
amount of dark matter. After imposing all phenomenological constraints except
for the muon $(g-2)_\mu,$ we show that the CMSSM parameter space is divided
into well separated regions with distinctive but in general heavy sparticle
mass spectra. Imposing the $(g-2)_\mu$ constraint introduces severe tension
between the high SUSY scale and the experimental measurements -- only the
slepton co-annihilation region survives with potentially testable sparticle
masses at the LHC. In the latter case the spin-independent DM-nucleon
scattering cross section is predicted to be below detectable limit at the
XENON100 but might be of measurable magnitude in the general case of light dark
matter with large bino-higgsino mixing and unobservably large scalar masses.Comment: 17 pages, 7 figures. v3: same as published versio

### Enhanced anti-deuteron Dark Matter signal and the implications of PAMELA

We show that the jet structure of DM annihilation or decay products enhances
the anti-deuterium production rate by orders of magnitude compared to the
previous computations done assuming a spherically symmetric coalescence model.
In particular, in the limit of heavy DM, M >> m_p, we get a constant rather
than 1/M^2 suppressed anti-deuterium production rate. Therefore, a detectable
anti-deuterium signal is compatible with the lack of an excess in the
anti-proton PAMELA flux. Most importantly, cosmic anti-deuterium searches
become sensitive to the annihilations or decays of heavy DM, suggesting to
extend the experimental anti-deuterium searches above the O(1) GeV scale.Comment: 13 pages, 7 figures. Final versio

### PPPC 4 DM ID: A Poor Particle Physicist Cookbook for Dark Matter Indirect Detection

We provide ingredients and recipes for computing signals of TeV-scale Dark
Matter annihilations and decays in the Galaxy and beyond. For each DM channel,
we present the energy spectra of electrons and positrons, antiprotons,
antideuterons, gamma rays, neutrinos and antineutrinos e, mu, tau at
production, computed by high-statistics simulations. We estimate the Monte
Carlo uncertainty by comparing the results yielded by the Pythia and Herwig
event generators. We then provide the propagation functions for charged
particles in the Galaxy, for several DM distribution profiles and sets of
propagation parameters. Propagation of electrons and positrons is performed
with an improved semi-analytic method that takes into account
position-dependent energy losses in the Milky Way. Using such propagation
functions, we compute the energy spectra of electrons and positrons,
antiprotons and antideuterons at the location of the Earth. We then present the
gamma ray fluxes, both from prompt emission and from Inverse Compton scattering
in the galactic halo. Finally, we provide the spectra of extragalactic gamma
rays. All results are available in numerical form and ready to be consumed.Comment: 57 pages with many figures and tables. v4: updated to include a 125
higgs boson, computation and discussion of extragalactic spectra corrected,
some other typos fixed; all these corrections and updates are reflected on
the numerical ingredients available at
http://www.marcocirelli.net/PPPC4DMID.html they correspond to Release 2.

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