Hadroproduction of t anti-t pair in association with an isolated photon at NLO accuracy matched with parton shower

We simulate the hadroproduction of a t anti-t pair in association with a hard photon at LHC using the PowHel package. These events are almost fully inclusive with respect to the photon, allowing for any physically relevant isolation of the photon. We use the generated events, stored according to the Les-Houches event format, to make predictions for differential distributions formally at the next-to-leading order (NLO) accuracy and we compare these to existing predictions accurate at NLO using the smooth isolation prescription of Frixione. We also make predictions for distributions after full parton shower and hadronization using the standard experimental cone-isolation of the photon.Comment: 21 pages, 17 figures, version accepted for publication in JHE

A subtraction scheme for computing QCD jet cross sections at NNLO: integrating the subtraction terms I

In previous articles we outlined a subtraction scheme for regularizing doubly-real emission and real-virtual emission in next-to-next-to-leading order (NNLO) calculations of jet cross sections in electron-positron annihilation. In order to find the NNLO correction these subtraction terms have to be integrated over the factorized unresolved phase space and combined with the two-loop corrections. In this paper we perform the integration of all one-parton unresolved subtraction terms

Hadroproduction of t anti-t pair with two isolated photons with PowHel

We simulate the hadroproduction of a t anti-t pair in association with two isolated hard photons at 13 TeV LHC using the PowHel package. We use the generated events, stored according to the Les-Houches event format, to make predictions for differential distributions formally at the next-to-leading order (NLO) accuracy. We present predictions at the hadron level employing the cone-type isolation of the photons used by experiments. We also compare the kinematic distributions to the same distributions obtained in the t anti-t H final state when the Higgs-boson decays into a photon pair, to which the process discussed here is an irreducible background.Comment: 18 pages, 11 figures, minor changes, version submitted for publicatio

Új fizika keresése a CERN CMS detektorával = Search for new physics with the CMS detector at CERN

A kiküldöttek munkájának eredményeként megvalósult a CMS müonkamrák helyzetmeghatározó rendszerének fejlesztésével, megépítésével, kipróbálásával és üzemeltetésével kapcsolatos összes célkitűzésünk. Megtörtént az első üzemi tapasztalatok összegyűjtése, az észlelt hibák javítása, és a felkészülés az új mérési időszakaszra. A tevékenység másik ága az őszi mérések kiértékelése, illetve a kiértékelési módszerek tökéletesítése volt a szerzett tapasztalatok alapján. A célkitűzéseken túlmenően foglalkoztunk a Pixel detektor időzítésével is. Kozmikus müonok segítségével a Pixel adatrögzítésének idejét a kozmikus eseményt kiválasztó detektor idejéhez hangoltuk, majd a Pixel detektor időzítését az LHC-ben történő első ütközésekhez igazítottuk, illetve a detektor moduljainak egyedi időzítését összehangoltuk. Az adatkiértékelés terén a szuperszimmetrikus jelenségek keresésében vettünk részt. Csoportunk csatlakozott a CMS SUSY-csoportjában alakult egy-leptonos alcsoporthoz és elvégezte a csoport által kijelölt RA4 referencia-analízist. Komoly előrelépés történt a proton-proton ütközésben hipotetikusan keletkező fekete lyukak modelljének vizsgálatában is: a BlackMax program segítségével szimulált adatokon vizsgáltuk a jelenség megfigyelésének lehetőségeit a CMS-nél. | As a result of the work carried out at CERN, our group achieved all the planned goals related to the CMS muon barrel positioning system: development, construction, testing and maintainance. We have collected the first experiences of operation, corrected the faulty elements and prepared to the new period of operation. The other segment of our activities was evaluation of the data from fall 2008 and the improvement of the data analysis software based upon the collected experiance during operation. In addition to the original plans, we also worked on the timing of the Pixel detector. Using cosmic muons we adjusted the time of data recording to the time of the subdetector that selected the cosmic event. Next, we adjusted the time of the Pixel detector to the time of the first collisions in the LHC. Furthermore, we synchronized the modules of the detector. In the field of data analysis we participated in searching for the manifestation of supersymmetry. Our group joined the single-lepton subgroup of the CMS SUSY working group and carried out the RA4 reference analysis requested by the subgroup. We also made significant advancement in studying the model for the production of microscopic black holes assumed in proton-proton collisions: using data simulated with the BlackMax computer program, we searched for channels of detection of such events at CMS

Precise prediction for the mass of the WW boson in gauged U(1) extensions of the standard model

We present the one-loop radiative corrections to the muon decay in U(1)$_z$ extensions of the standard model. We compute the mass of the $W$ boson using those corrections and compare it to an approximation of the complete one-loop prediction implemented in automated computational tools. We point out that the truncation of the complete formulas become unreliable if the mass of the $Z'$ boson, corresponding to the new U(1)$_z$ gauge group is larger than about 1 TeV.Comment: 13 pages, 2 figure