We evaluate the Configurational Entropy (CE) for scalar mesons and for JP=12+ baryons in a holographic approach, varying the dimension of boundary theory operators and using the soft-wall dual model ...of QCD. We find that hybrid and multiquark mesons are characterized by an increasingly large CE. A similar behavior is observed for JP=12+ baryons, where the CE of pentaquarks is larger than for three-quark baryons, for same radial number. Configurational Entropy seems relevant in disentangling conventional hadrons from exotica.
A
bstract
Inclusive semileptonic decays of beauty baryons are studied using the heavy quark expansion to
O
1
/
m
b
3
, at leading order in
α
s
. The case of a polarized decaying baryon is examined, ...with reference to Λ
b
. An extension of the Standard Model effective Hamiltonian inducing
b
→
U
ℓ
ν
¯
ℓ
transitions (
U
=
u, c
and
ℓ
=
e, μ, τ
) is considered, which comprises the full set of D=6 semileptonic operators with left-handed neutrinos. The effects of the new operators in several observables are described.
On the decay mode Λb → Xsγ Colangelo, P.; De Fazio, F.; Loparco, F.
The journal of high energy physics,
10/2023, Volume:
2023, Issue:
10
Journal Article
Peer reviewed
Open access
A
bstract
We study the inclusive
H
b
→ X
s
γ
decay with
H
b
a beauty baryon, in particular Λ
b
, employing an expansion in the heavy quark mass at
O
m
b
−
3
at leading order in
α
s
, keeping the ...dependence on the hadron spin. For a polarized baryon we compute the distribution
d
2
Γ
dy
d
cos
θ
P
, with
y
= 2
E
γ
/
m
b
,
E
γ
the photon energy and
θ
P
the angle between the baryon spin vector and the photon momentum in the
H
b
rest-frame. We discuss the correlation between the baryon and photon polarization, and show that effects of physics beyond the Standard Model can modify the photon polarization asymmetry. We also discuss a method to treat the singular terms in the photon energy spectrum obtained by the OPE.
The Large Area Telescope (LAT) onboard the Fermi satellite is a pair-conversion telescope for high-energy gamma rays of astrophysical origin. Although it was designed to be a high-sensitivity ...gamma-ray telescope, the LAT has proved to be an excellent electron/positron detector. It has been operating in low Earth orbit since June 2008 and has collected more than 16 million cosmic-ray electron and positron (CRE) events in its first seven years of operation. The huge data sample collected by the LAT enables a precise measurement of the CRE energy spectrum up to the TeV region. A search for anisotropies in the arrival directions of CREs was also performed. The upper limits on the dipole anisotropy probe the presence of nearby young and middle-aged CRE sources.
When seen in gamma rays, the Moon appears brighter than the Sun. Gamma rays emitted by the Moon mostly originate from the decays of neutral pions produced by the interactions of cosmic rays with the ...lunar surface. Using the data collected by the Fermi Large Area Telescope (LAT) in its first seven years of operation, we measured the gamma-ray emission spectrum of the Moon in the energy range from 30MeV up to a few GeV and we studied its time evolution, finding a correlation with the solar activity. We also developed a full Monte Carlo simulation based on the FLUKA code, which describes the production of gamma rays in the cosmic-ray interactions with the Moon. We used the simulation results to infer the cosmic-ray proton and helium spectra near the Earth from the lunar gamma-ray data.
Abstract
All known small solar system bodies have diameters between a few meters and a few thousands of kilometers. Based on the collisional evolution of solar system bodies, a larger number of ...asteroids with diameters down to ∼2 m is thought to exist. As all solar system bodies, small bodies can be passive sources of high-energy gamma-rays, produced by the interaction of energetic cosmic rays impinging on their surfaces. Since the majority of known asteroids are in orbits between Mars and Jupiter (in a region known as the Main Belt), we expect them to produce a diffuse emission close to the ecliptic plane. In this work, we have studied the gamma-ray emission coming from the ecliptic using the data collected by the Large Area Telescope (LAT) onboard the Fermi satellite. We have fit the results with simulations of the gamma-ray intensity at the source level (calculated with the software
FLUKA
) to constrain the small solar system bodies population. Finally, we have proposed a model describing the distribution of asteroid sizes and we have used the LAT data to constrain the gamma-ray emission expected from this model and, in turn, on the model itself.
Relations among Bc→ J/ψ, ηc form factors Colangelo, P.; De Fazio, F.; Loparco, F. ...
The journal of high energy physics,
5/9, Volume:
2022, Issue:
9
Journal Article
Peer reviewed
Open access
A
bstract
We analyze the form factors parametrizing the
B
c
→ J/ψ, η
c
matrix elements of the operators in a generalized low-energy
b → c
semileptonic Hamiltonian. We consider an expansion in ...nonrelativistic QCD, classifying the heavy quark spin symmetry breaking terms and expressing the form factors in terms of universal functions in a selected kinematical range. Using as an input the lattice QCD results for the
B
c
→
J/ψ
matrix element of the SM operator, we obtain information on other form factors. The extrapolation to the full kinematical range is also presented.
Dark matter particles from the galactic halo can be gravitationally trapped in the solar core or in external orbits. The enhanced density of dark matter particles either in the solar core or in ...external orbits can result in the annihilation of these particles producing gamma rays via long-lived intermediate states or directly outside the Sun, respectively. These processes would yield characteristic features in the energy spectrum of the subsequent gamma rays, i.e., a boxlike or linelike shaped feature, respectively. We have performed a dedicated analysis using a 10-year sample of gamma-ray events from the Sun collected by the Fermi Large Area Telescope searching for spectral features in the energy spectrum as a signature of dark matter annihilation. In the scenario of gamma-ray production via long-lived mediators, we have also evaluated the dark matter-nucleon spin-dependent and spin-independent scattering cross section constraints from the flux limits in a dark matter mass range from 3 GeV/c2 up to about 1.8 TeV /c2. In the mass range up to about 150 GeV/c2, the limits are in the range 10−46 – 10−45 cm2 for the spin-dependent scattering and in the range 10−48 – 10−47 cm2 for the spin-independent case. The range of variation depends on the decay length of the mediator.
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