91 research outputs found
Stripping Cross Sections in Collisions of Light Nuclei
By evaluating all the contributions of the intermediate states of the
multiple scattering theory diagrams, we compute the integrated stripping cross
sections of collisions among light nuclei. The resulting expressions have the
simple form of a combination of total inelastic cross sections of nuclear
reactions with projectile nuclei differing in the atomic mass number. We also
check the accuracy of some widely used relations in heavy ion collisions.Comment: 9 pages, 4 figures, Latex fil
Multi-parton correlations and "exclusive" cross sections
In addition to the inclusive cross sections discussed within the QCD-parton
model, in the regime of multiple parton interactions, different and more
exclusive cross sections become experimentally viable and may be suitably
measured. Indeed, in its study of double parton collisions, the quantity
measured by CDF was an "exclusive" rather than an inclusive cross section. The
non perturbative input to the "exclusive" cross sections is different with
respect to the non perturbative input of the inclusive cross sections and
involves correlation terms of the hadron structure already at the level of
single parton collisions. The matter is discussed in details keeping explicitly
into account the effects of double and of triple parton collisions.Comment: 18 pages, no figures, corrected typo
Finite formation time effects in inclusive and semi-inclusive electro-disintegration of few-body nuclei
Finite Formation Time (FFT) effects in the exclusive reaction ^4He(e,e'p)^3H
at high values of Q^2 are introduced and discussed. It is shown that the
minimum in the momentum distributions predicted by the Plane Wave Impulse
Approximation (PWIA), which is filled by the Glauber-type Final State
Interaction (FSI), is completely recovered when FFT effects are taken into
account. The semi-inclusive process ^4 He(e,e'p)X is also investigated.Comment: 4 pages, 2 eps figure
Final state interaction in inclusive and exclusive quasi-elastic processes
We discuss a new approach to final state interactions, that keeps explicitly
into account the virtuality of the ejected nucleon in quasi-elastic
scattering at very large , and we present some recent results, at
moderately large values, for the nuclear transparency in ,
and and for the momentum distributions of .Comment: 10 pages, 5 figures, Prepared for the workshop "Cortona 2000, VIII
Convegno su Problemi di Fisica Nucleare Teorica
Collisions of protons with light nuclei shed new light on nucleon structure
The high rates of multi-parton interactions at the LHC can provide a unique
opportunity to study the multi-parton structure of the hadron. To this purpose
high energy collisions of protons with nuclei are particularly suitable. The
rates of multi-parton interactions depend in fact both on the partonic
multiplicities and on the distributions of partons in transverse space, which
produce different effects on the cross section in pA collisions, as a function
of the atomic mass number A. Differently with respect to the case of
multi-parton interactions in pp collisions, the possibility of changing the
atomic mass number provides thus an additional handle to distinguish the
diverse contributions. Some relevant features of double parton interactions in
pD collisions have been discussed in a previous paper. In the present paper we
show how the effects of double and triple correlation terms of the multi-parton
structure can be disentangled, by comparing the rates of multiple parton
interactions in collisions of protons with D, Tritium and 3He.Comment: 50 pages, 13 figure
Inclusive and "exclusive" cross sections in the regime of multiple parton collisions
The large luminosity and the increased kinematical domain accessible at the
LHC will allow to isolate large numbers of events with multiple parton
collisions. Interestingly, the hadron is probed in different points
contemporarily in the process, which allows to obtain information on the
correlations between partons in the hadron structure. The whole experimentally
accessible information on multiple parton collisions consists in the
probability distribution of the elementary interactions, while the inclusive
cross sections, usually considered in large p_t processes, acquire a precise
statistical meaning as moments of the multiplicity distribution. Conversely
different and more "exclusive" cross sections become experimentally viable,
providing complementary information on the interaction dynamics. The matter is
discussed in details in the case of hadron-hadron collisions and the role of
parton correlations is outlined both in the inclusive and in the "exclusive"
cross sections.Comment: 18 pages, no figures, corrected typo
Medium Modifications from 4He(e,e'p)3H
Polarization transfer in quasi-elastic nucleon knockout is sensitive to the
properties of the nucleon in the nuclear medium, including possible
modification of the nucleon form factor and/or spinor. In our recently
completed experiment E03-104 at Jefferson Lab we measured the proton recoil
polarization in the 4He(e,e'p)3H reaction at a Q^2 of 0.8 (GeV/c)^2 and 1.3
(GeV/c)^2 with unprecedented precision. These data complement earlier data
between 0.4 and 2.6 (GeV/c)^2 from both Mainz and Jefferson Lab. The measured
ratio of polarization-transfer coefficients differs from a fully relativistic
calculation, favoring either the inclusion of a medium modification of the
proton form factors predicted by a quark-meson coupling model or strong
charge-exchange final-state interactions. The measured induced polarizations
agree well with the fully relativistic calculation and indicate that these
strong final-state interactions may not be applicable.Comment: 7 pages, 3 figures. Based on invited talk presented by S. Strauch at
"Sixth International Conference on Perspectives in Hadronic Physics", ICTP,
Trieste, May 12-16, 200
Homozygous FVII deficiencies with different reactivity towards tissue thromboplastins of different origin.
The reagents most frequently used for FVII activity assay are obtained by rabbit brain or human placenta. In recent years, human recombinant thromboplastins have received great attention. FVII activity in FVII deficiency is usually low, regardless of the thromboplastin used. There are a few exceptions to this rule. These are represented by FVII Padua (Arg304Gln), FVII Nagoya (Arg304Trp), and FVII (Arg79Gln). In these three instances, clear discrepancies were noted in the FVII activity depending on the thromboplastin used. This indicates that at least two areas of FVII are involved in tissue binding, namely an epidermal growth factor domain of the light chain (Arg79Gln) and the catalytic domain (Arg304), controlled by exons 4 and 8, respectively. Since these three variants are cross reactive material positive, namely they are Type 2 defects, all other variants with normal antigen should be investigated by a panel of at least three tissue thromboplastins (rabbit brain, human tissue or human recombinant, and ox brain derived) in order to obtain a satisfactory classification
Production and detection of doubly charmed tetraquarks
The feasibility of tetraquark detection is studied. For the cc\bar{u}\bar{d}
tetraquark we show that in present (SELEX, Tevatron, RHIC) and future
facilities (LHCb, ALICE) the production rate is promising and we propose some
detectable decay channels.Comment: 6 pages, 5 figure
Measuring Double Parton Distributions in Nucleons at Proton-Nucleus Colliders
We predict a strong enhancement of multijet production in proton-nucleus
collisions at collider energies, as compared to a naive expectation of a cross
section . The study of the process would allow to measure, for the
first time, the double parton distribution functions in a nucleon in a model
independent way and hence to study both the longitudinal and the transverse
correlations of partons.Comment: 12 pages, 2 figure
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