619 research outputs found
Phenomenology of TMDs
We present a review of current Transverse Momentum Dependent (TMD)
phenomenology focusing our attention on the unpolarized TMD parton distribution
function and the Sivers function. The paper introduces and comments about the
new Collins-Soper-Sterman (CSS) TMD evolution formalism. We make use of a
selection of results obtained by several groups to illustrate the achievements
and the failures of the simple Gaussian approach and the TMD CSS evolution
formalism.Comment: 10 pages, 5 figures, to appear in the proceedings of the TRANSVERSITY
2014, Chia, Italy, 9-13 June, 201
The Boer-Mulders effect in unpolarized SIDIS: an analysis of the COMPASS and HERMES data on the asymmetry
We present a phenomenological analysis of the asymmetry
recently measured by the COMPASS and HERMES collaborations in unpolarized
semi-inclusive deep inelastic scattering. In the kinematical regimes explored
by these experiments the asymmetry arises from transverse-spin and intrinsic
transverse-momentum effects. We consider the leading-twist contribution,
related to the so-called Boer-Mulders transverse-polarization distribution
, and the twist-4 Cahn contribution, involving
unpolarized transverse-momentum distribution functions. We show that a
reasonably good fit of the data is achieved with a Boer-Mulders function
consistent with the main theoretical expectations. Our conclusion is that the
COMPASS and HERMES measurements represent the first experimental evidence of
the Boer-Mulders effect in SIDIS.Comment: 11 pages, 7 figures, published version in PR
Azimuthal asymmetries in unpolarized Drell-Yan processes and the Boer-Mulders distributions of antiquarks
Using a previous extraction of the quark Boer-Mulders distributions from
semiinclusive deep inelastic scattering data, we fit the unpolarized Drell-Yan
data on the asymmetry, determining the antiquark Boer-Mulders
distributions. A good agreement with the data is found in the region of low
, where the transverse-momentum factorization approach applies.Comment: 7 pages, 3 figure
Non-perturbative QCD effects in spectra of Drell-Yan and -boson production
The factorization theorems for transverse momentum distributions of
dilepton/boson production, recently formulated by Collins and
Echevarria-Idilbi-Scimemi in terms of well-defined transverse momentum
dependent distributions (TMDs), allows for a systematic and quantitative
analysis of non-perturbative QCD effects of the cross sections involving these
quantities. In this paper we perform a global fit using all current available
data for Drell-Yan and -boson production at hadron colliders within this
framework. The perturbative calculable pieces of our estimates are included
using a complete resummation at next-to-next-to-leading-logarithmic accuracy.
Performing the matching of transverse momentum distributions onto the standard
collinear parton distribution functions and recalling that the corresponding
matching coefficient can be partially exponentiated, we find that this
exponentiated part is spin-independent and resummable. We argue that the
inclusion of higher order perturbative pieces is necessary when data from lower
energy scales are analyzed. We consider non-perturbative corrections both to
the intrinsic nucleon structure and to the evolution kernel and find that the
non-perturbative part of the TMDs could be parametrized in terms of a minimal
set of parameters (namely 2-3). When all corrections are included the global
fit so performed gives a and a very precise
prediction for vector boson production at the Large Hadron Collider (LHC).Comment: 24 pages, 11 figures. v2: new subsection added, discussion on the
stability of the calculations and on higher order contributions improved,
results unchange
Atlas and Informative System of the Lagoon of Venice: updated tools for a higher management efficiency in Natura 2000 sites
La laguna di Venezia è un ecosistema complesso
per comprendere il quale è necessario integrare
dati ed informazioni provenienti da discipline
diverse raccolti da differenti Enti ed Istituti di
ricerca. L’Osservatorio Naturalistico della
Laguna, del Comune di Venezia, nasce
fondamentalmente per raccogliere queste
informazioni ed organizzarle affinché possano
essere fruibili sia dai vari Servizi e Direzioni dell’Amministrazione Comunale, sia dalle
istituzioni scientifiche e dai cittadini. Per questo
motivo è stato prodotto l’Atlante della Laguna,
una raccolta di 103 mappe tematiche, ciascuna
delle quali è corredata da una scheda esplicativa,
suddivise in 5 sezioni: Geosfera, Biosfera,
Antroposfera, Ambiti di Tutela e Analisi Integrate.
L’Atlante rappresenta solo un primo passo verso
la diffusione e la validazione dei dati ambientali.
Attualmente si sta realizzando un Sistema
Informativo della Laguna (SIL) che metterà
a disposizione di vari utenti le informazioni,
le elaborazioni ed i materiali raccolti
dall’Osservatorio durante le sue attività (in parte
già sintetizzati nell’Atlante). Il passo successivo
sarà la raccolta e la diffusione delle informazioni
e dei dati che altri soggetti proprietari vorranno
inserire nel SIL, attraverso appositi protocolli di
scambio. I vantaggi di un Sistema Informativo
rispetto ad un volume cartaceo sono molteplici
e noti, e vanno dall’aggiornabilità del dato alla
possibilità di elaborarlo secondo necessità
contingenti. L’utilizzo di questi strumenti per la
gestione delle aree umide è esemplificato
attraverso un caso studio: la Valutazione di
Incidenza dell’area utilizzata per il tiro al piattello
localizzata a Campalto (Venezia), attività
dismessa ormai da diversi anni.The lagoon of Venice is a complex ecosystem
that can be understood only by the integration of
data and information with a multidisciplinary
approach. The ‘Osservatorio Naturalistico della
Laguna’ of Venice Municipality has been created
with the aim of gathering and organizing all kinds
of information, so that it can be used by
administrators, scientific institutions and
citizens. For this reason, the Lagoon Atlas was
produced. The Atlas is composed by 103 tematic
maps, each accompanied by an explicatory
schedule, subdivided into 5 sections:
Geosphere, Biosphere, Anthroposphere,
Protection and Integrated Analysis.
The Atlas represents a first step towards the
distribution and validation of environmental data.
An Informative System of the Lagoon (SIL) is
currently under construction, and this will allow to obtain all kind of information, elaboration and
materials gathered by the Osservatorio during its
activities (already partially summarized in the
Atlas). The next step will be to gather and
distribute information and data that other
subjects will include in the SIL, through specific
protocols of exchange. The advantages of using
an Informative System rather than paper
materials are obvious, spanning from the
possibility to update data to the possibility of
elaborating them according to the needs.
The use of these tools for wetland management
is exemplified by a case study: the assessment
of projects in the area of Campalto (Venice), that
in the past was used for shooting
Phenomenology of TMDs Using SCET
We present a global fit of current available data for Drell-Yan and Z-boson production using the Transverse Momentum Dependent evolution formalism of Refs. [1–4]. We performed our analysis including perturbative calculable contributions up to next-to-next-to-leading-logarithmic accuracy. We took into account non-perturbative corrections both to the intrinsic nucleon structure and to the evolution kernel
TMDs: Evolution, modeling, precision
The factorization theorem for spectra in Drell-Yan processes, boson
production and semi-inclusive deep inelastic scattering allows for the
determination of the non-perturbative parts of transverse momentum dependent
parton distribution functions. Here we discuss the fit of Drell-Yan and
-production data using the transverse momentum dependent formalism and the
resummation of the evolution kernel. We find a good theoretical stability of
the results and a final . We show how the fixing
of the non-perturbative pieces of the evolution can be used to make predictions
at present and future colliders.Comment: 6 pages, 3 pdf figures, uses webofc.cls. Invited talk delivered by I.
Scimemi at the Fourth International Workshop on "Transverse Polarisation
Phenomena in Hard Processes" (Transversity 2014), Chia, Cagliari, Italy, June
9-13, 2014. To appear in EPJ Web of Conference
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