Szuperszimmetrikus részecskék keresése nagyenergiájú proton-proton ütközésekben = Serch for supersymmetric particles in high energy proton-proton collisions

A Genf székhelyű, összeurópai finanszírozású Európai Részecskefizikai Központban (CERN) épülő új gyorsító, az LHC előreláthatólag 2008-ban - a világon elsőként -14 TeV energiájú proton-proton ütközéseket szolgáltat. Ezzel lehetővé válik, hogy az elemi részecskék közötti kölcsönhatásokat és az azokban megnyilvánuló szimmetria tulajdonságokat minden eddiginél magasabb energiatartományban kísérletileg is tanulmányozhassuk. Ennek érdekében a Marseillei Részecskefizikai Központ (CPPM) kutatóival együtt részt vettünk a mintegy 150 laboratórium 1600 fizikusát egyesítő ATLAS kollaboráció épülő detektora elektromágneses kalorimétere záróegységeinek megépítésében: az ezt alkotó modulok összeszerelésében, elektronikus tesztjeiben, különböző részecskenyalábokkal történő besugárzásában és az így nyert adatok kiértékelésében. Létrehoztuk a záróegységek működését leíró számítógépes programrendszer számos elemét. Modelleztük a detektorban lejátszódó elektromágneses folyamatokat, új algoritmust definiáltunk a sokszoros Coulomb szórás leírására. Vizsgáltuk a záróegységek fizikai tulajdonságait, így pl. energia- és térfelbontó képességüket. Megállapítottuk, hogy ezek összhangban vannak a tervezett paraméterekkel, ami lehetővé teszi, hogy a záróegységeket mind a precíziós mérésekben, mind pedig a proton-proton ütközésekben keletkező események energiaegyensúlyának kiértékelésében eredményesen használhassuk | The Large Hadron Collider (LHC) is under construction at the Organization Européenne pour la Recherche Nucléaire (CERN), Genf, Switzerland. It is going to provide world highest energy proton-proton collisions of 14 TeV in 2008. This makes a unique possibility to study experimentally the interactions and symmetry features of the elementary particles in a not yet studied energy region. Together with the physics group of the Centre de Physique des Particules de Marseille (CPPM), we participated in several aspects of the construction of the endcaps of the electromagnetic calorimeter (EMEC) of the Atlas collaboration, an organization including about 1500 physicists of 150 laboratories around the world. We contributed to the assembly, electrical tests, data recording and analysis taken at the CERN's test beam irradiation of the EMEC modules. We worked out several items of the EMEC simulation software. Computer models of the electromagnetic interactions taking place in the material of the detector were studied and improved. A new algorithm to describe the multiple Coulomb scattering was created and implemented into the Geant4 simulation software. Physics performance (energy and space resolution, particle identification capability etc.) of EMEC modules was proven to be compatible with the design specifications. This makes possible to use these detectors, as part of the Atlas detector complex, in high precision measurements and measuring energy balance of the future p-p collisons at LHC

Simple scalable nucleotic FPGA based short read aligner for exhaustive search of substitution errors

With the advent of the new and continuously improving technologies, in a couple of years DNA sequencing can be as commonplace as a simple blood test. The growth of sequencing efficiency has a larger exponent than the Moore’s law of standard processors, hence alignment and further processing of sequenced data is the bottleneck. The usage of FPGA (Field Programmable Gate Arrays) technology may provide an efficient alternative. We propose a simple algorithm for DNA sequence alignment, which can be realized efficiently by nucleotic principal agents of Non.Neumann nature. The prototype FPGA implementation runs on a small Terasic DE1-SoC demo board with a Cyclone V chip. We present test results and furthermore analyse the theoretical scalability of this system, showing that the execution time is independent of the length of reference genome sequences. A special advantage of this parallel algorithm is that it performs exhaustive search producing all match variants up to a predetermined number of point (mutation) errors

Gravitational waves from spinning eccentric binaries

This paper is to introduce a new software called CBwaves which provides a fast and accurate computational tool to determine the gravitational waveforms yielded by generic spinning binaries of neutron stars and/or black holes on eccentric orbits. This is done within the post-Newtonian (PN) framework by integrating the equations of motion and the spin precession equations while the radiation field is determined by a simultaneous evaluation of the analytic waveforms. In applying CBwaves various physically interesting scenarios have been investigated. In particular, we have studied the appropriateness of the adiabatic approximation, and justified that the energy balance relation is indeed insensitive to the specific form of the applied radiation reaction term. By studying eccentric binary systems it is demonstrated that circular template banks are very ineffective in identifying binaries even if they possess tiny residual orbital eccentricity. In addition, by investigating the validity of the energy balance relation we show that, on contrary to the general expectations, the post-Newtonian approximation should not be applied once the post-Newtonian parameter gets beyond the critical value $\sim 0.08-0.1$. Finally, by studying the early phase of the gravitational waves emitted by strongly eccentric binary systems---which could be formed e.g. in various many-body interactions in the galactic halo---we have found that they possess very specific characteristics which may be used to identify these type of binary systems.Comment: 37 pages, 18 figures, submitted to Class. Quantum Gra

The basic physics of the binary black hole merger GW150914

The first direct gravitational-wave detection was made by the Advanced Laser Interferometer Gravitational Wave Observatory on September 14, 2015. The GW150914 signal was strong enough to be apparent, without using any waveform model, in the filtered detector strain data. Here, features of the signal visible in the data are analyzed using concepts from Newtonian physics and general relativity, accessible to anyone with a general physics background. The simple analysis presented here is consistent with the fully general-relativistic analyses published elsewhere,in showing that the signal was produced by the inspiral and subsequent merger of two black holes. The black holes were each of approximately 35 Msun, still orbited each other as close as ~350 km apart, and subsequently merged to form a single black hole. Similar reasoning, directly from the data, is used to roughly estimate how far these black holes were from the Earth, and the energy that they radiated in gravitational waves

Results of the deepest all-sky survey for continuous gravitational waves on LIGO S6 data running on the Einstein@Home volunteer distributed computing project

We report results of a deep all-sky search for periodic gravitational waves from isolated neutron stars in data from the S6 LIGO science run. The search was possible thanks to the computing power provided by the volunteers of the Einstein@Home distributed computing project. We find no significant signal candidate and set the most stringent upper limits to date on the amplitude of gravitational wave signals from the target population. At the frequency of best strain sensitivity, between 170.5 and 171 Hz we set a 90% confidence upper limit of 5.5 × 10−25, while at the high end of our frequency range, around 505 Hz, we achieve upper limits ' 10−24. At 230 Hz we can exclude sources with ellipticities greater than 10−6 within 100 pc of Earth with fiducial value of the principal moment of inertia of 1038kg m2. If we assume a higher (lower) gravitational wave spindown we constrain farther (closer) objects to higher (lower) ellipticities