|
YOUNG RESEARCHERS WORKSHOP
| MONDAY 7th |
| THEORY |
| 17:00-17:15 |
Naser Ahmadiniaz
(Universidad Michoacana - Morelia, Mexico):
A compact representation of the three-gluon vertex
The three-gluon vertex, that is, the one-particle
irreducible off-shell Green's function, is a basic quantity in
perturbative QCD. It contains essential information on the IR
divergence structure of QCD, and is an important ingredient of the
Schwinger-Dyson equations. It has been studied by Ball
and Chiu, Cornwall and Papavassiliou, Binger and Brodsky, and others.
I present here a recent calculation of this vertex in the worldline
formalism which is simpler, and also leads to a significantly
more compact form factor decomposition of the vertex function. The
relation to the effective action is shortly discussed.
|
| 17:15-17:30 |
Pietro Dall' Olio
(Universidad Michoacana - Morelia, Mexico)
:
Infrared behavior of the propagators in Yang-Mills theory
It is widely known that in QCD the infrared region is not available to
perturbative calculations due to the presence of a Landau pole in the
running of the coupling constant. Non perturbative solutions of the
propagators in Yang-Mills theory are presented by solving numerically
a truncated system of Dyson-Schwinger equations and are compared with
analytical results found by applying the Renormalization Group
equations in an epsilon expansion to the infrared fixed point, when a
mass term for the gluon is added to the action.
|
| 17:30-17:45 |
Simona Salvini
(University of Trieste - Trieste, Italy)
:
Double Parton Interactions in Proton Deuteron Collision
Multiple Parton Interactions are the tool to obtain information on the
correlations between partons in the hadron structure. As in the case
of high energy proton-proton collisions the effects of correlations in
the transverse coordinates and in fractional momenta are unavoidably
mixed in the final observables, it is convenient to study Multiple
Parton Interactions in high energy hadron-nucleus
collisions. Non-trivial features appear already in the simplest case,
double parton scattering in proton-deuteron collisions, where non
negligible off-diagonal terms arise.
|
| 17:45-18:00 |
Beatrice Murdaca
(University of Calabria - Cosenza, Italy)
:
Production of jets widely separated in rapidity in proton collisions
The Mueller-Navelet jet production process was suggested
as an ideal tool to study the Regge limit of perturbative Quantum
ChromoDynamics (QCD) in proton-proton (or proton-antiproton)
collisions. We calculate, within the BFKL approach and at the
next-to-leading order, the jet vertex relevant for the analysis of
this process. We consider both processes with incoming quark and gluon. The starting
point is the definition of quark and gluon impact factors in the BFKL
approach. Following this procedure we show explicitly
that all infrared divergences cancel when renormalized parton
densities are considered.
|
| 18:00-18:15 |
Jose' Garcia (Cinvestav - Mexico D.F., Mexico)
:
Lorentz violation in a 5D susy model
One of the goals of the LHC is the search for the existence of physics
Beyond Standar Model, because of that, topics like Supersymmetry
(SUSY), Extra Dimensions (XD) and others have taken additional
relevance in the- oretical research. In this work we present a SUSY
model in 5D which does not have lorentz invariance in the extra
dimension, and the rupture of this symmetry is given in an explicit
way. The preservation of the SUSY features is possible iff its
generators are deform in agreement to the form of the breaking
terms. Also, we present a possible treatment in the superfield
formalism.
|
| 18:15-18:30 |
Audrey Degee (Liege U., Belgium)
:
Minimal lepton flavor violating realizations
of minimal seesaw models
We study the implications of the global $U(1)_R$ symmetry present in
minimal lepton flavor violating extensions of the seesaw. In the
context of explicit minimal seesaw setups with a slightly broken
$U(1)_R$, we show that depending on the $R$-charge assignments two
classes of generic models can be identified. Models where the
right-handed neutrino masses and the lepton number breaking scale
are decoupled, and models where the parameters that slightly break
$U(1)_R$ induce a suppression in the light neutrino mass
matrix. Within the second class of scenarios we studied the effects
of the right-handed neutrinos interactions on charged lepton flavor
violating decays and on preexisting primordial $B-L$ asymmetries,
finding that sizable lepton flavor violating $\mu$ processes are
incompatible with preserving a primordial $B-L$ asymmetry consistent
with the observed baryon asymmetry of the Universe.
|
| ASTROPHYSICS |
| 18:30-18:45 |
Roberto Iuppa (Tor Vergata U. - Rome, Italy)
:
Anisotropy in the Cosmic Radiation at TeV energy
In recent years very important results were obtained from cosmic ray
experiments about the arrival direction distribution of primaries in the
TeV energy range. As most of these particles are charged nuclei, they
are deflected by the magnetic field they pass through before reaching
the Earth surface, the effect of the Lorentz force being inversely
proportional to the particle energy. As far as the local interstellar
medium is known, the gyroradius of a 10 TeV proton is expected to be
only 100 a.u., small enough to make the arrival direction distribution
isotropic. Since 1930s a "large scale" ( anisotropy is known
to exist, generally interpreted as the combined effect of sources far
away and magnetic fields nearby. Nonetheless, in the last decade
experiments like Tibet-ASg, Milagro, ARGO-YBJ and IceCube discovered
structures as wide as all over the sky at ~10 TeV energy, what
is unexplainable within the standard model of cosmic rays.
In this talk a review of the most recent experimental results about
cosmic ray anisotropy is given, together with the status of the art of
theoretical efforts aimed at interpreting them within the current cosmic
ray paradigma.
|
| 18:45-19:00 |
Beatrice Panico (Tor Vergata U. - Rome, Italy -
ARGO-YBJ Collaboration)
:
Measurement of the Cosmic Rays primary spectrum with
ARGO-YBJ experiment
The study of cosmic rays physic of 1012-1015 primary cosmic energy is one
of the main goals of ARGO-YBJ experiment. The detector, located at the
Yangbajing Cosmic Ray Laboratory (Tibet, 4300 m a.s.l., 606 g/cm2), is
an EAS array consisting of a continuous carpet of RPCs. The low energy
threshold of the detector allows to study an energy region characterized by
the transition from the direct to the indirect measurements. In this talk we
will report on the measurement of the cosmic rays energy spectrum at different
zenith angles. The phenomenology of horizontal air shower ($\theta$ >
will be described and discussed.
|
|
THURSDAY 10th
|
| THEORY |
| 17:00-17:15 |
Sergi Gonzalez-Solis (Autonoma Barcelona U. - Barcelona, Spain)
:
$\eta-\eta'$ mixing angle from the semileptonic decays
$D_{(s)} ->
\eta(\eta') e+ \nu_e$ and $B -> \eta(\eta') \ell \nu$
It is well known that semileptonic decays of B, D and $D_s$ mesons are
very rich in phenomenology. We canangle $\phi$. extract valuable information of
several physical observables from measurements of these decays such
for instance precise results in the CKM sector of the Standard Model
crucial to constrain the unitarity of the CKM matrix. In
addition, these are proper mesons to study the phenomenology of the
$\eta$ and $\eta'$ mesons. In the present work we focalize our study
in the semileptonic decays $D_{(s)} -> \eta(\eta') e+ \nu_e$ and $B ->
\eta(\eta') \ell \nu$ from which we obtain the $\eta - eta'$ mixing angle $\psi$.
|
| 17:15-17:30 |
Dmitriy V. Matvienko (BINP, Novosibirsk)
:
Model of the decay $B^0 -> D^* \omega \pi$ and analysis status at Belle.
We constructed a model of the $B^0 -> D^* \omega \pi$ decay in which
the decay amplitude is a sum of intermediate $\omega \pi$ and $D^*
\pi$-states with different spins and perform MC simulation based on
the obtained expressions. This model is convenient for Dalitz plot
analysis. Using the Belle data on $\Upsilon(4S) -> B anti-B$,
corresponding to an integrated luminosity of 711 fb^-1, we report a
status of analysis of the B^0 - > D^* \omega \pi$ decay.
|
| 17:30-17:45 |
Simone Biondini (Technische Universitat Munchen - Germany)
:
Phenomenology of doubly charged excited leptons at LHC
We consider the production at the LHC of exotic composite leptons of
charge Q = +2e. Such states are allowed in composite models which
contain extended isospin multiplets (I_{W} = 1 and I_{W} = 3/2). These
doubly charged leptons couple with Standard Model fermions via
gauge interactions. We discuss the production cross section at the
LHC of L++ (pp -> L++, l-) and concentrate on the leptonic
signature deriving from the cascade decays L++ -> W+l+ -> l+ l+ \nu l
i.e. p p -> l- (l+ l+) \nu l. We provide the features of a
possible detection of L++ within the framework of a general purpose
detector at the LHC using the Pretty Good Simulator software.
|
|
EXPERIMENTAL
|
| 17:45-18:00 |
Giordano Cattani (Tor Vergata U. - Rome, Italy)
:
Forward-backward asymmetry measurement in pp -> Z/gamma* -> mu+mu-
events at $\sqrt{s}$ = 7 TeV with the ATLAS experiment at the LHC
Muon pairs can be produced through the Drell-Yan process over a large
invariant mass range at CERN Large Hadron Collider (LHC). In the
Standard Model of particle physics, the process occurs to first
order via qqbar annihilation into a real (or virtual) Z boson or a
virtual photon (gamma*). The presence of both vector and axial-vector
couplings of the fermions to the Z boson gives rise to a
forward-backward asymmetry (Afb) in the distribution of the polar
angle $\theta*$ of the negatively charged lepton relative to the
incoming quark direction in the rest frame of the lepton pair. This
asymmetry is particularly useful in searching for new interactions at
large momentum transfers ($Q^2 = (m^2)_{\mu\mu}$) where
$(m^2)_{\mu\mu}$ is the invariant mass of the muon pair. Indeed, the
asymmetry shape would be modified by new resonances (e.g. additional
heavier Z' bosons) or new interactions at large mass scales.
Moreover, the measurement of Afb can also improve QCD measurements
with higher order corrections, constraint Parton Distribution
Functions (PDFs) and be used to extract basic SM parameters. In this
talk I will present the measurement of the mass dependence of the
forward-backward asymmetry in pp -> Z/gamma* -> mu+mu- interactions,
corresponding to ~ 5.0 fb$^{-1}$ of integrated luminosity collected by
the ATLAS experiment at the LHC at $\sqrt{s}$ = 7 TeV during 2011. The
effective weak mixing angle ($\theta_{eff}$) from this process,
involving predominantly the first generation of quarks, is extracted
as $\sin^2\theta_{eff}$ and a preliminary result will be presented.
|
| 18:00-18:15 |
Federico Meloni (Milano U. - Milan, Italy)
:
ATLAS searches for supersymmetry at LHC
Supersymmetry with large
mixing angle predicts that the lightest superpartners of the SM
fermions belong to the third generation. Furthermore, naturalness
arguments favor masses not too far from the top quark mass. This talk
presents the status of the searches for supersymmetric particles with
the ATLAS detector at LHC, in proton proton collisions at sqrt(s)=7
TeV. It has been possible to put stringent limits on many
supersymmetric particle masses and extend the search for scalar
partners of the third generation, both in direct and gluino mediated
production.
|
| 18:15-18:30 |
Valerio Ippolito (La Sapienza U. - Rome, Italy)
:
Search for Higgs boson in the four lepton final state with the ATLAS
experiment
Results of a search for the Standard Model Higgs boson at the ATLAS
experiment in the decay channel H->ZZ(*)->4 l where l=e,mu are
presented. Data collected in p-p collisions at sqrt(s) = 7 TeV for a
total integrated luminosity of about 5 fb-1 are compared to the
Standard Model expectations and upper limits on the production cross
section of a SM Higgs boson in the mass range 100 - 600 GeV are set.
|
| 18:30-18:45 |
Andrea Gabrielli (La Sapienza U. - Rome, Italy)
:
Search for Hidden Higgs decays in the ATLAS detector
Hidden Valley models predict Higgs decays to neutral
particles. These particles can be also long lived with decay paths
comparable to the LHC detectors dimensions. Decay final states consist
of collimated leptons (Lepton Jets) or heavy flavors. Results are
presented of a search for Higgs decays to long lived particles in the
ATLAS detector at the LHC with a 7 TeV center of mass energy, based
on ~2fb-1 data collected during 2011.
|
| 18:45-19:00 |
Valerio Bortolotto (Roma Tre U. - Rome, Italy)
:
Search for the Higgs boson in the H->WW->l nu l nu channel
I will report the recent results for the Standard Model Higgs Boson
searches using 4.7 fb-1 of proton-proton collisions data at sqrt(s)=7TeV,
recorded with the ATLAS detector at the Large Hadron Collider. The
analysis considers decay channels H->WW->l nu l nu where l = (e or mu) with
final states containing a charged leptons and missing transverse energy.
The event selection, the background composition extraction methods and the
evaluation of systematics are detailed. The strategy used for the analysis
cut optimisation will be detailed.
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