113 research outputs found
b -> s gamma in a calculable model of Electroweak Symmetry Breaking
In a recently proposed extension of the Standard Model with a compact extra
dimension of size R we compute the leading corrections, of relative order (m_t
R)^2, to the Branching Ratio B -> X_s gamma. For 1/R = 370 \pm 80 GeV, the
branching ratio is increased in a significant way relative to the SM, although
not al level of being inconsistent with present measurements.Comment: 14 pages, Latex, 2 eps figures, minor changes, to appear on
Nucl.Phys.
Breaking the electroweak symmetry and supersymmetry by a compact extra dimension
We revisit in some more detail a recent specific proposal for the breaking of
the electroweak symmetry and of supersymmetry by a compact extra dimension.
Possible mass terms for the Higgs and the matter hypermultiplets are considered
and their effects on the spectrum analyzed. Previous conclusions are reinforced
and put on firmer ground.Comment: 25 pages, LaTeX, 9 eps figure
Neutrino oscillations and large extra dimensions
Assuming that right-handed neutrinos exist and propagate in some large extra
dimensions, we attempt to give a comprehensive description of the phenomenology
of neutrino oscillations. A few alternative explanations of the atmospheric
neutrino anomaly emerge, different from the standard nuMu --> nuTau or nuMu -->
nuSterile interpretations. Constraints from nucleosynthesis and supernova 1987a
are discussed. The constraints from SN1987a indicates a maximum radius of any
extra dimension of about 1 Angstrom.Comment: 12 pages, 5 figures. Version 2: misprints fixed, ref.s added,
conclusions modified: at least in minimal models the maximal radius of large
extra dimensions where right-handed neutrinos can propagate must be smaller
than an atom in order to satisfy bounds from the 1987 supernov
Graviscalars from higher-dimensional metrics and curvature-Higgs mixing
We investigate the properties of scalar fields arising from gravity
propagating in extra dimensions. In the scenario of large extra dimensions,
proposed by Arkani-Hamed, Dimopoulos and Dvali, graviscalar Kaluza-Klein
excitations are less important than the spin-2 counterparts in most processes.
However, there are important exceptions. The Higgs boson can mix to these
particles by coupling to the Ricci scalar. Because of the large number of
states involved, this mixing leads, in practice, to a sizeable invisible width
for the Higgs. In the Randall-Sundrum scenario, the only graviscalar is the
radion. It can be produced copiously at hadron colliders by virtue of its
enhanced coupling to two gluons through the trace anomaly of QCD. We study both
the production and decay of the radion, and compare it to the Standard Model
Higgs boson. Furthermore, we find that radion detectability depends crucially
on the curvature-Higgs boson mixing parameter.Comment: 34 pages, late
Transplanckian Collisions at the LHC and Beyond
Elastic collisions in the transplanckian region, where the center-of-mass
energy is much larger than the fundamental gravity mass scale, can be described
by linearized general relativity and known quantum-mechanical effects as long
as the momentum transfer of the process is sufficiently small. For larger
momentum transfer, non-linear gravitational effects become important and,
although a computation is lacking, black-hole formation is expected to dominate
the dynamics. We discuss how elastic transplanckian collisions can be used at
high-energy colliders to study, in a quantitative and model-independent way,
theories in which gravity propagates in flat extra dimensions. At LHC energies,
however, incalculable quantum-gravity contributions may significantly affect
the experimental signal.Comment: 45 pages, 9 figures. v2: added refs and expanded discussion of
fixed-angle string scatterin
A DROP-IN beta probe for robot-assisted 68Ga-PSMA radioguided surgery: first ex vivo technology evaluation using prostate cancer specimens
Background: Recently, a flexible DROP-IN gamma-probe was introduced for robot-assisted radioguided surgery, using traditional low-energy SPECT-isotopes. In parallel, a novel approach to achieve sensitive radioguidance using beta-emitting PET isotopes has been proposed. Integration of these two concepts would allow to exploit the use of PET tracers during robot-assisted tumor-receptor-targeted. In this study, we have engineered and validated the performance of a novel DROP-IN beta particle (DROP-INβ) detector. Methods: Seven prostate cancer patients with PSMA-PET positive tumors received an additional intraoperative injection of ~ 70 MBq 68Ga-PSMA-11, followed by robot-assisted prostatectomy and extended pelvic lymph node dissection. The surgical specimens from these procedures were used to validate the performance of our DROP-INβ probe prototype, which merged a scintillating detector with a housing optimized for a 12-mm trocar and prograsp instruments. Results: After optimization of the detector and probe housing via Monte Carlo simulations, the resulting DROP-INβ probe prototype was tested in a robotic setting. In the ex vivo setting, the probeâpositioned by the robotâwas able to identify 68Ga-PSMA-11 containing hot-spots in the surgical specimens: signal-to-background (S/B) was > 5 when pathology confirmed that the tumor was located < 1 mm below the specimen surface. 68Ga-PSMA-11 containing (and PET positive) lymph nodes, as found in two patients, were also confirmed with the DROP-INβ probe (S/B > 3). The rotational freedom of the DROP-IN design and the ability to manipulate the probe with the prograsp tool allowed the surgeon to perform autonomous beta-tracing. Conclusions: This study demonstrates the feasibility of beta-radioguided surgery in a robotic context by means of a DROP-INβ detector. When translated to an in vivo setting in the future, this technique could provide a valuable tool in detecting tumor remnants on the prostate surface and in confirmation of PSMA-PET positive lymph nodes. Š 2020, The Author(s)
N=4 Supergravity Lagrangian for Type IIB Orientifold on T^6/Z_2 in Presence of Fluxes and D3-Branes
We derive the Lagrangian and the transformation laws of N=4 gauged
supergravity coupled to matter multiplets whose sigma-model of the scalars is
SU(1,1)/U(1)x SO(6,6+n)/SO(6)xSO(6+n) and which corresponds to the effective
Lagrangian of the Type IIB string compactified on the T^6/Z_2 orientifold with
fluxes turned on and in presence of n D3-branes. The gauge group is T^12 x G
where G is the gauge group on the brane and T^12 is the gauge group on the bulk
corresponding to the gauged translations of the R-R scalars coming from the R-R
four--form. The N=4 bulk sector of this theory can be obtained as a truncation
of the Scherk-Schwarz spontaneously broken N=8 supergravity. Consequently the
full bulk spectrum satisfies quadratic and quartic mass sum rules, identical to
those encountered in Scherk-Schwarz reduction gauging a flat group. This theory
gives rise to a no scale supergravity extended with partial super-Higgs
mechanism.Comment: 49 pages, LaTex, 2 figures. Misprints corrected, more comments adde
Stability and efficiency of a CMOS sensor as detector of low energy beta and gamma particles
Radio Guided Surgery (RGS) is a nuclear medicine technique allowing the surgeon to identify tumor residuals in real time with a millimetric resolution, thanks to a radiopharmaceutical as tracer and a probe as detector. The use of beta(-) emitters, instead of gamma or beta(+), has been recently proposed with the aim to increase the technique sensitivity and reducing both the administered activity to the patient and the medical exposure. In this paper, the possibility to use the commercial CMOS Image Sensor MT9V115, originally designed for visible light imaging, as beta(-) radiation detector RGS is discussed. Being crucial characteristics in a surgical environment, in particular its stability against time, operating temperature, integration time and gain has been studied on laboratory measurements. Moreover, a full Monte Carlo simulation of the detector has been developed. Its validation against experimental data allowed us to obtain efficiency curves for both beta and gamma particles, and also to evaluate the effect of the covering heavy resin protective layer that is present in the "off the shelf" detector. This study suggests that a dedicated CMOS Image Sensor (i.e. one produced without the covering protective layer) represents the ideal candidate detector for RGS, able to massively increase the amount of application cases and the efficacy of this technique
Monitoring Carbon Ion Beams Transverse Position Detecting Charged Secondary Fragments: Results From Patient Treatment Performed at CNAO
Particle therapy in which deep seated tumours are treated using 12C ions (Carbon Ions RadioTherapy or CIRT) exploits the high conformity in the dose release, the high relative biological effectiveness and low oxygen enhancement ratio of such projectiles. The advantages of CIRT are driving a rapid increase in the number of centres that are trying to implement such technique. To fully profit from the ballistic precision achievable in delivering the dose to the target volume an online range verification system would be needed, but currently missing. The 12C ions beams range could only be monitored by looking at the secondary radiation emitted by the primary beam interaction with the patient tissues and no technical solution capable of the needed precision has been adopted in the clinical centres yet. The detection of charged secondary fragments, mainly protons, emitted by the patient is a promising approach, and is currently being explored in clinical trials at CNAO. Charged particles are easy to detect and can be back-tracked to the emission point with high efficiency in an almost background-free environment. These fragments are the product of projectiles fragmentation, and are hence mainly produced along the beam path inside the patient. This experimental signature can be used to monitor the beam position in the plane orthogonal to its flight direction, providing an online feedback to the beam transverse position monitor chambers used in the clinical centres. This information could be used to cross-check, validate and calibrate, whenever needed, the information provided by the ion chambers already implemented in most clinical centres as beam control detectors. In this paper we study the feasibility of such strategy in the clinical routine, analysing the data collected during the clinical trial performed at the CNAO facility on patients treated using 12C ions and monitored using the Dose Profiler (DP) detector developed within the INSIDE project. On the basis of the data collected monitoring three patients, the technique potential and limitations will be discussed
Standalone vertex ďŹnding in the ATLAS muon spectrometer
A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at âs = 7 TeV collected with the ATLAS detector at the LHC during 2011
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