A. Radi

Application of fringes of equal chromatic order for investigating the effect of temperature on optical parameters of a GRIN optical fibre

Multiple-beam white light interference fringes across a GRIN optical fibre immersed in a liquid wedge interferometer placed in front of a grating spectrograph are produced. They are used to investigate the effect of temperature on the optical fibre parameters of both the cladding (pure SiO2) and the core (GeO2-doped SiO2). A two-term Sellmeier dispersion relation is adopted and fitted to the experimental refractive index data. Then a temperature-dependent Sellmeier formula is deduced to study the effect of temperature on the refractive index of the fibre and its dispersion in addition to all of its optical parameters. These parameters are the average energy gap, the variation of the thermo-optic coefficient with photon energy, the refractive index difference, the numerical aperture, the normalized frequency (V-number), the number of modes, the material dispersion and the zero-dispersion wavelength.

Beam test results for new full-scale GEM prototypes for a future upgrade of the CMS high-η Muon System

The CMS GEM collaboration is considering Gas Electron Multipliers (GEMs) for upgrading the CMS forward muon system in the 1.5 <; |η| <; 2.4 endcap region. GEM detectors can provide precision tracking and fast trigger information. They would improve the CMS muon trigger and muon momentum resolution and provide missing redundancy in the high-η region. Employing a new faster construction and assembly technique, we built four full-scale Triple-GEM muon detectors for the inner ring of the first muon endcap station. We plan to install these or further improved versions in CMS during the first long LHC shutdown in 2013/14 for continued testing. These detectors are designed for the stringent rate and resolution requirements in the increasingly hostile environments expected at CMS after the second long LHC shutdown in 2018/19. The new prototypes were studied in muon/pion beams at the CERN SPS. We discuss our experience with constructing the new full-scale production prototypes and present preliminary performance results from the beam test. We also tested smaller Triple-GEM prototypes with zigzag readout strips with 2 mm pitch in these beams and measured a spatial resolution of 73 μm. This readout offers a potential reduction of channel count and consequently electronics cost for this system while maintaining high spatial resolution.

Interferometric determination of gamma radiation effects on optical parameters of a GRIN optical fibre

Multiple-beam white-light interference fringes across an irradiated GRIN fibre, of length 2 cm and immersed in a liquid wedge interferometer that is followed by a grating spectrograph, are produced. These fringes are used to investigate the effect of gamma radiation, with different doses from 0.01 to 1 MGy, on the optical parameters of both the cladding (pure silica) and the core (germanium-doped silica) of the GRIN fibre. Optical parameters such as refractive index, refractive index difference, numerical aperture, V-number, index profile, chromatic dispersion and zero-dispersion wavelength are determined and studied. A two-term Sellmeier dispersion relation is adopted and fitted to the experimental data of the refractive index. Then, a dose-dependent Sellmeier formula is deduced to represent the effect of gamma radiation on different optical parameters.

Status of the Triple-GEM project for the upgrade of the CMS Muon System

The CMS GEM collaboration is performing a feasibility study to install triple-GEM detectors in the forward region of the muon system (1.6 < vertical bar eta vertical bar < 2.4) of the CMS detector at the LHC. Such micro-pattern gas detectors are able to cope with the extreme particle rates that are expected in that region during the High Luminosity phase of the LHC. With their spatial resolution of order 100 micron GEMs would not only provide additional benefits in the CMS muon High Level Trigger, but also in the muon identification and track reconstruction, effectively combining tracking and triggering capabilities in one single device. The present status of the full project will be reviewed, highlighting all importants steps and achievements since the start of the R& D in 2009. Several small and full-size prototypes were constructed with different geometries and techniques. The baseline design of the triple-GEM detector for CMS will be described, along with the results from extensive test measurements of all prototypes both in the lab and in test beams at the CERN SPS. The proposed on-and off-detector electronics for the final system will be presented.

GENETIC PROGRAMING MODELING FOR NUCLEUS–NUCLEUS COLLISIONS

High Energy Physics (HEP), due to the vast and complex data expected from current and future experiments, is in need of powerful and efficient techniques for various analysis tasks. Genetic Programing (GP) is a powerful technique that can be used such complex tasks. In this paper, Genetic programing is used for modeling the functions that describe the pseudo-rapidity distribution of the shower particles for 12C, 16O, 28Si and 32S on nuclear emulsion and also to predict the distributions that are not present in the training set and matched them effectively. The proposed method shows a better fitting with experimental data. The GP prediction results prove a strong presence modeling in heavy ion collisions.

Artificial Neural Network And Genetic Algorithm Hybrid Technique For Nucleus–Nucleus Collisions

Selecting the optimal topology of a neural network for a particular application is a difficult task. Genetic Algorithm (GA) has been used to find the optimal neural network (NN) solution (i.e., hybrid technique) to calculate the pseudo-rapidity distribution of the shower particles for C12, O16, Si28, and S32 on nuclear emulsion. An efficient NN has been designed by GA to predict the distributions that are not present in the training set and matched them effectively. The proposed method shows a better fitting with experimental data. The hybrid technique GA–ANN simulation results prove a strong presence modeling in heavy ion collisions.

Discovered Function For Positron Collisions With Alkali-Metal Atoms Using Genetic Programming

Genetic programming (GP) has been used to discover the function that describes the collisions of positrons with sodium, potassium, rubidium and cesium atoms at low and intermediate energies. The GP has been running based on experimental data of the total collisional cross sections to produce the total cross sections for each target atom. The incident energy and the static dipole polarizability of the alkali target atom have been used as input variables to find the discovered function. The experimental, calculated and predicted total collisional cross sections are compared. The discovered function shows a good match to the experimental data. We find that the GP technique is able to improve upon more traditional methods. To our knowledge, this is the first application of the GP technique to the data of positron collisions with alkali atoms at low and intermediate energies.

Development of the data acquisition system for the Triple-GEM detectors for the upgrade of the CMS forward muon spectrometer

In this contribution we will report on the progress of the design of the readout and data acquisition system being developed for triple-GEM detectors which will be installed in the forward region (1.5 < |?| < 2.2) of the CMS muon spectrometer during the 2nd long shutdown of the LHC, expected in the period 2017?2018. The system will be designed to take full advantage of current generic developments introduced for the LHC upgrades. The current design is based on the use of CERN GLIB boards hosted in micro-TCA crates for the off-detector electronics and the Versatile Link with the GBT chipset to link the front-end electronics to the GLIB boards. In this contribution we will describe the physics goals, the hardware architectures and report on the expected performance of the CMS GEM readout system, including preliminary timing resolution simulations.

A study of film and foil materials for the GEM detector proposed for the CMS muon system upgrade

During the next shutdown of the LHC at CERN, the CMS experiment plans to start installing GEM detectors in the endcap (high pseudorapidity) region. These muon detectors have excellent spatial and temporal resolution as well as a high chemical stability and radiation hardness. A report is given on preliminary results of materials studies that aimed to fully characterize the GEM detector components before and after the exposure to a high-radiation environment.

GENETIC PROGRAMMING APPROACH FOR ELECTRON-ALKALI-METAL ATOM COLLISIONS

New technique is presented for modeling the total cross sections of electron scattering by Na, K, Rb and Cs atoms in the low and intermediate energy regions. The calculations have been performed in the framework of genetic programming (GP) technique. The GP has been running based on the experimental data of the total collisional cross sections to produce the total cross sections for each target atom. The incident energy and atomic number as well as the static dipole polarizability have been used as input variables to find the functions that describe the total collisional cross sections of the scattering of electrons by alkali atoms. The experimental, calculated and predicted total collisional cross sections are compared. The discovered functions show a good match to the experimental data.