Narrow Results

The well-known formula det (A · B) = det A · det B can be easily proved for finite dimensional matrices but it may be incorrect for the functional determinants of differential operators, including the ones which are relevant for Quantum Field Theory applications. Considerable work has been done to prove that this equality can be violated, but in all previously known cases the difference could be reduced to renormalization ambiguity. We present the first example, where the difference between the two functional determinants is a nonlocal expression and therefore can not be explained by the renormalization ambiguity. Moreover, through the use of other even dimensions we explain the origin of this difference at qualitative level.

After nearly one and a half centuries of effort, one of the most pernicious problems in observational astronomy — obtaining resolved images of the stars — is finally yielding to advances in modern instrumentation. The exquisite precision delivered by today's interferometric observatories is rapidly being applied to more and more branches of optical astronomy. The most capable interferometers in the Northern Hemisphere, both located in the United States are the Navy Precision Optical Interferometer (NPOI) in Arizona and the Center for High Angular Resolution Astronomy Array (CHARA) run by Georgia State University and located in California. In early 2013 these two groups held a joint meeting hosted by the Lowell Observatory in Flagstaff. All major groups working in the field were represented at this meeting and it was suggested to us by this Journal that this was an excellent opportunity to put together a special issue on interferometry. In order to be as broad as possible, those who did not attend the CHARA/NPOI meeting were also solicited to make a contribution. The result is this collection of papers representing a snap shot of the state of the art of ground based optical and near infrared interferometry.

COMPASS is a multi-purpose fixed-target experiment at CERN aimed at studying the structure and spectrum of hadrons. It has collected the so far world’s largest data set on diffractive production of the K⁻π⁻π⁺ decay, which in principle gives access to all kaon states. We performed an elaborate partial-wave analysis, using model-selection techniques to select the wave set based on a large systematically constructed pool of allowed partial waves. The partial- wave decomposition reveals signals in the mass region of well-known states, such as K₁(1270) and K₁(1400). In addition, we observe potential signals from excited states, such as K₁(1650).

We investigate the Schmid theorem, which states that if one has a tree level mechanism with a particle decaying to two particles and one of them decaying posteriorly to two other particles, the possible triangle singularity developed by the mechanism of elastic rescattering of two of the three decay particles does not change the cross section provided by the tree level. We investigate the process in terms of the width of the unstable particle produced in the first decay and determine the limits of validity and violation of the theorem.

Over the past two years, the use of on-shell techniques has deepened our understanding of the S-matrix of gauge theories and led to the calculation of many new scattering amplitudes. In these notes we review a particular on-shell technique developed recently, the quantum MHV diagrams, and discuss applications to one-loop amplitudes. Furthermore, we briefly discuss the application of D-dimensional generalised unitarity to the calculation of scattering amplitudes in non-supersymmetric Yang-Mills.

We present on the use of on-shell recursion relations. These can be used not only for calculating tree amplitudes, including those with masses, but also to compute analytically the missing rational terms of one-loop QCD amplitudes. Combined with the cut-containing pieces calculated using a unitarity approach complete one-loop QCD amplitudes can be derived. This approach is discussed in the context of the adjacent 2-minus all-multiplicity QCD gluon amplitude.

The High Resolution Fly's Eye (HiRes) Experiment has been in operation in monocular mode since 1997. The HiRes results on the cosmic ray spectrum are consistent with the GZK Suppression at 10^19.8 eV and observes an ankle structure at 10^18.5 eV. Composition studies of Hires stereo data shows a predominantly light composition in the energy range 10^18.0 – 10^19.3 eV. We also report on the result of the proton-air cross section measurement from the tails of the X_MAX distribution. Various anisotropy studies have yielded null results. However, an apparent correlation between HiRes stereo events and BL-Lac objects has been reported.

We discuss peculiarities of open-quantum systems, as compared to closed quantum systems. We emphasize the importance of taking continuum degrees of freedom into account when dealing with systems with a tendency to decay through emission of fragments. In this context we introduce the Coupled-Cluster theory, and argue that this method allows for an accurate description of such systems starting from nucleon-nucleon degrees of freedom. We present Ab-initio Coupled Cluster calculations with singles and doubles excitations (CCSD) for the ground states of the helium isotopes ^3–10He. The calculated masses and decay widths are in semi-quantitative agreement with experiment. The discrepancy with experiment is suspected to be attributed to the three-nucleon force (3NF) which is not included at this point.

The isovector giant dipole resonance (GDR) in deformed nuclei ¹⁵⁴Sm and ²³⁸U is described within the self-consistent separable RPA (random-phase-approximation) with Skyrme forces SkT6, SkM*, SLy6 and SkI3. We examine dependence of the description on the Skyrme force and gross-structure effects, as well as influence of the Coulomb interaction, multipole mixing, and time-odd densities. The results are analyzed in terms of isovector characteristics of the nuclear matter. It is shown that GDR in deformed nuclei can serve as a robust test for Skyrme forces with different effective masses. The best description of the resonance is obtained for the SLy6 force.

We have studied the spin-one resonance dominated form factors governing the radiative decay of the π, within the framework of resonance chiral theory. We obtain predictions for their value at zero momentum transfer and also a description of their q² dependence. We also fit the possible new physics tensor coupling.

The atmospheric Cherenkov telescope MAGIC for ground-based gamma-ray astronomy is operating since late 2003 on the Canarian island La Palma. The telescope's 17 m diameter mirror is composed of 964 light weight, square all-aluminum mirrors of 234 m² total area, which allows to lower the energy threshold to a value far beyond that of past generation of telescopes. The trigger system, based on ultra-fast decision logics (topological, time-coincidences, etc.) is designed to cope with very fast PMT signals (2 ns). Details of the MAGIC telescope will be presented, technical problems and solutions will be discussed as well as a report on three years of operations will be given.

One of the fundamental questions still open in elementary particle is the nature of the neutrino mass. Whether Dirac or Majorana, its knowledge would deeply impact the development of the field. Double Beta Decay experiments are, although extremely challenging, the only way known that might give an answer to the question. In this paper one of the second generation experiment that aims to get the sensitivity for probing the inverted hierarchy will be discussed. It is CUORE, in preparation at the Gran Sasso underground laboratories of INFN.

MAGIC, a 17m diameter Cherenkov telescope located on the Canary Island of La Palma, is the biggest IACT (Imaging Atmospheric Cherenkov Telescope) in the world. For lowering the energy threshold and improving the sensitivity, the MAGIC collaboration is currently building a second telescope (MAGIC II), using Photomultipliers(PMTs) with a better sensitivity. Various measurements of different characteristics of PMTs, such as single photoelectron spectrum(SPE), afterpulse, aging and photoelectron detection were performed. The results from selected PMT candidates of different companies will be presented here.

The CMS experiment is getting ready to take data at the LHC accelerator at CERN. Due to late delivery of the experimental caverns the detector had to be pre-assembled on the surface and lowered in large segments. This has constrained the commissioning strategy of the experiment. Global commissioning has started in Spring of 2007 and has progressed in parallel with the construction and assembly of detector and services underground. This paper describes the strategy adopted in order to commission components of the system in incremental steps in order to be ready to accept collisions from LHC with a well debugged and understood system, including the detector, acquisition system, trigger, software, computing and data shipping.

The CMS detector at the CERN Large Hadron Collider (LHC) is equipped with a redundant muon system based on Drift Tubes Chambers (barrel region) and Cathode Strip Chamber (endcap region), and Resistive Plate Chamber (RPC). During the summer and fall 2006 a first integrated test of an entire CMS slice was performed at the SX5 experimental surface hall. The RPC chambers were operated with cosmic rays. The results on the RPC performance are reported.

The ATLAS experiment is a multi-purpose particle detector that will study high-energy particle collisions produced by the Large Hadron Collider at CERN. In order to achieve its physics goals, the ATLAS tracking requires that the positions of the silicon detector elements have to be known to a precision better than 10 μm. Several track-based alignment algorithms have been developed for the Inner Detector. An extensive validation has been performed with simulated events and real data coming from the ATLAS. Results from such validation are reported in this paper.

The Rare ISotopes INvestigation project combines the fragment recoil separator at GSI with a high-efficiency Germanium array. The project focuses on studies of shell evolution far off stability, pn-pairing, symmetries and nuclear shapes utilizing projectile fragmentation beams. Highlights from a few recent experiments performed at RISING are reported.

Paths of test particles, rotating and charged objects in brane-worlds using a modified Bazanski Lagrangian are derived. We also discuss the transition to their corresponding equations in four dimensions. We then make a comparison between the given equations in brane-worlds (BW) and their analog in space-time-matter (STM) theory.

We present the current status of the search for new physics effects in the mixing quantities ΔM_s, ΔΓ_s and ɸ_s of the neutral B_s-system.

The h-BN and graphene films on Si substrates were prepared by RF magnetron sputtering and CVD techniques, respectively. Structures and morphologies of these films were analyzed by IR and Raman spectroscopies and scanning electronic microscopy. Thermal conductivities of bulk Si and Si substrate with h-BN or graphene grown were measured and compared. Results indicate that both h-BN and graphene films have an enhancement effect on the TC of the Si substrate even if they are not single-layer. Our findings imply that the h-BN and graphene films may have good applications as a thermal management material to help heat dissipation in semiconductor devices.