Planar channeling and quasichanneling oscillations in a bent crystal

Particles passing through a crystal under planar channeling experience transverse oscillations in their motion. As channeled particles approach the atomic planes of a crystal, they are likely to be dechanneled. This effect was used in ion-beam analysis with MeV energy. We studied this effect in a bent crystal for positive and negative particles within a wide range of energies in sight of application of such crystals at accelerators. We found the conditions for the appearance or not of channeling oscillations. Indeed a new kind of oscillations, strictly related to the motion of over-barrier particles, i.e. quasichanneling particles, has been predicted. Such oscillations, named planar quasichanneling oscillations, possess a different nature than channeling oscillations. Through computer simulation, we studied this effect and provided a theoretical interpretation for them. We show that channeling oscillations can be observed only for positive particles while quasichanneling oscillations can exist for particles with either sign. The conditions for experimental observation of channeling and quasichanneling oscillations at existing accelerators with available crystal has been found and optimized.Comment: 25 pages, 11 figure

Electromagnetic dipole moments of charged baryons with bent crystals at the LHC

We propose a unique program of measurements of electric and magnetic dipole moments of charm, beauty and strange charged baryons at the LHC, based on the phenomenon of spin precession of channeled particles in bent crystals. Studies of crystal channeling and spin precession of positively- and negatively-charged particles are presented, along with feasibility studies and expected sensitivities for the proposed experiment using a layout based on the LHCb detector.Comment: 19 pages, 13 figure

Experimental evidence of planar channeling in a periodically bent crystal

The usage of a Crystalline Undulator (CU) has been identified as a promising solution for generating powerful and monochromatic $\gamma$-rays. A CU was fabricated at SSL through the grooving method, i.e., by the manufacturing of a series of periodical grooves on the major surfaces of a crystal. The CU was extensively characterized both morphologically via optical interferometry at SSL and structurally via X-ray diffraction at ESRF. Then, it was finally tested for channeling with a 400 GeV/c proton beam at CERN. The experimental results were compared to Monte Carlo simulations. Evidence of planar channeling in the CU was firmly observed. Finally, the emission spectrum of the positron beam interacting with the CU was simulated for possible usage in currently existing facilities

Steering efficiency of a ultrarelativistic proton beam in a thin bent crystal

Crystals with small thickness along the beam exhibit top performance for steering particle beams through planar channeling. For such crystals, the effect of nuclear dechanneling plays an important role because it affects their efficiency. We addressed the problem through experimental work carried out with 400 GeV/c protons at fixed-target facilities of CERN-SPS. The dependence of efficiency vs. curvature radius has been investigated and compared favourably to the results of modeling. A realistic estimate of the performance of a crystal designed for LHC energy including nuclear dechanneling has been achieved

ITGB2 mutation combined with deleted ring 21 chromosome in a child with leukocyte adhesion deficiency

Leukocyte adhesion deficiency type 1(LAD-1) is a rare autosomal recessive primary immunodeficiency caused by defects in the ITGB2 gene located on chromosome 21q22. Clinically, LAD-1 patients are characterized by recurrent infections, slow wound healing and dystrophic scars after skin injuries, associated with persistent neutrophilia. The severity of symptoms is related to the level of CD11/CD18 expression on patients’ leucocytes and those with less than 1% expression treated with hematopoietic stem cell transplant (HSCT). We present a child affected by LAD-1 who received HSCT from a matched unrelated donor. Molecular analysis revealed apparent homozygosis for a point mutation in the ITGB2 gene, only the mother however was carrier of the mutation. Cytogenetic and FISH analysis showed the presence of a de-novo ring chromosome 21. Whole Genome Analysis with the Affymetrix GeneChip Human Mapping 250K NspI array confirmed in the child the presence of a de novo deletion of the chromosomal region 21q22.3-qter, where the ITGB2 gene maps. While HSCT resulted in successful engraftment and correction of the immunodeficiency, all the phenotypic features of ring (21) syndrome with a deletion of a 4.6Mb (including 69 genes) clearly remained unchange

A deep 1.4 GHz survey of the J1030 equatorial field: a new window on radio source populations across cosmic time

We present deep L-Band observations of the equatorial field centered on the z=6.3 SDSS QSO, reaching a 1 sigma sensitivity of ~2.5 uJy at the center of the field. We extracted a catalog of 1489 radio sources down to a flux density of ~12.5 uJy (5 sigma) over a field of view of ~ 30' diameter. We derived the source counts accounting for catalog reliability and completeness, and compared them with others available in the literature. Our source counts are among the deepest available so far, and, overall, are consistent with recent counts' determinations and models. We detected for the first time in the radio band the SDSS J1030+0524 QSO (26 +/- 5 uJy). We derived its optical radio loudness R_O = 0.62 +/- 0.12, which makes it the most radio quiet AGN at z >~ 6 discovered so far and detected at radio wavelengths. We unveiled extended diffuse radio emission associated with the lobes of a bright FRII radio galaxy located close to the center of the J1030 field, which is likely to become the future BCG of a protocluster at z=1.7. The lobes' complex morphology, coupled with the presence of X-ray diffuse emission detected around the FRII galaxy lobes, may point toward an interaction between the radio jets and the external medium. We also investigated the relation between radio and X-ray luminosity for a sample of 243 X-ray-selected objects obtained from 500 ks Chandra observations of the same field, and spanning a wide redshift range (0 ~< z ~< 3). Focused on sources with a spectroscopic redshift and classification, we found that sources hosted by ETG and AGN follow Log(L_R)/Log(L_X) linear correlations with slopes of ~0.6 and ~0.8, respectively. This is interpreted as a likely signature of different efficiency in the accretion process. Finally, we found that most of these sources (>~87%) show a radio-to-X-ray radio loudness R_X < -3.5, classifying these objects as radio quiet.Comment: 18 pages, 15 figures, 5 table. Accepted for publication in A&

Strong Reduction of the Effective Radiation Length in an Axially Oriented Scintillator Crystal

We measured a considerable increase of the emitted radiation by 120 GeV/c electrons in an axially oriented lead tungstate scintillator crystal, if compared to the case in which the sample was not aligned with the beam direction. This enhancement resulted from the interaction of particles with the strong crystalline electromagnetic field. The data collected at the external lines of the CERN Super Proton Synchrotron were critically compared to Monte Carlo simulations based on the Baier-Katkov quasiclassical method, highlighting a reduction of the scintillator radiation length by a factor of 5 in the case of beam alignment with the [001] crystal axes. The observed effect opens the way to the realization of compact electromagnetic calorimeters or detectors based on oriented scintillator crystals in which the amount of material can be strongly reduced with respect to the state of the art. These devices could have relevant applications in fixed-target experiments, as well as in satellite-borne γ telescopes

A deep 1.4 GHz survey of the J1030 equatorial field: A new window on radio source populations across cosmic time

We present deep L-Band observations of the equatorial field centered on the z = 6.3 Sloan Digital Sky Survey (SDSS) quasar (QSO). This field is rich of multiwavelength photometry and spectroscopy data, making it an ideal laboratory for galaxy evolution studies. Our observations reach a 1σ sensitivity of ~2.5 μJy at the center of the field. We extracted a catalog of 1489 radio sources down to a flux density of ~12.5 μJy (5σ) over a field of view of ~ 30′ diameter. We derived the source counts accounting for catalog reliability and completeness, and compared them with others available in the literature. Our source counts are among the deepest available so far, and, overall, are consistent with recent counts'determinations and models. They show a slight excess at flux densities ~50 μJy, possibly associated with the presence of known overdensities in the field. We detected for the first time in the radio band the SDSS J1030+0524 QSO (26 ± 5 μJy, 8σ significance level). For this object, we derived an optical radio loudness RO = 0.62±0.12, which makes it the most radio quiet among active galactic nuclei (AGN) discovered so far at z ≳ 6 and detected at radio wavelengths. We unveiled extended diffuse radio emission associated with the lobes of a bright Fanaroff-Riley type II (FRII) radio galaxy located close to the center of the J1030 field, which is likely to become the future brightest cluster galaxy of a protocluster at z = 1.7. The lobes'complex morphology, coupled with the presence of X-ray diffuse emission detected around the FRII galaxy lobes, may point toward an interaction between the radio jets and the external medium. We also investigated the relation between radio and X-ray luminosity for a sample of 243 X-ray-selected objects obtained from 500 ks Chandra observations of the same field, and spanning a wide redshift range (0 ≲ z ≲ 3). Focused on sources with a spectroscopic redshift and classification, we found that sources hosted by early-type galaxies and AGN follow log(LR)/log(LX) linear correlations with slopes of ~0.6 and ~0.8, respectively. This is interpreted as a likely signature of different efficiency in the accretion process. Finally, we found that most of these sources (≳87%) show a radio-to-X-ray radio loudness RX ≲ -3.5, classifying these objects as radio quiet

A high-performance custom photodetection system to probe the light yield enhancement in oriented crystals

Scintillating homogeneous detectors represent the state of the art in electromagnetic calorimetry. Moreover, the currently neglected crystalline nature of the most common inorganic scintillators can be exploited to achieve an outstanding performance boost in terms of compactness and energy resolution. In fact, it was recently demonstrated by the AXIAL/ELIOT experiments that a strong reduction in the radiation length inside PWO, and a subsequent enhancement in the scintillation light emitted per unit thickness, are attained when the incident particle trajectory is aligned with a crystal axis within $\sim 1^\circ$. A SiPM-based system has been developed to directly probe this remarkable effect by measuring the scintillation light emitted by a PWO sample. The same concept could be applied to full-scale detectors that would feature a design significantly more compact than currently achievable and unparalleled resolution in the range of interest for present and future experiments