Heavy ion physics at CMS and ATLAS: hard probes

Hard probes are indispensable tools to study the hot and dense quark-gluon matter created in ultra-relativistic heavy ion collisions. These probes are created in the collision itself with a small cross section, and they serve as indicators of various properties of the medium, such as temperature, viscosity, energy density, transport coefficients. Hard probes measured by the CMS and ATLAS experiments at the LHC include highly energetic jets and charged particles, quarkonium states, and electroweak gauge bosons. An overview of those recent experimental results will be given that represent the path towards high-precision measurements, even in the challenging, high-multiplicity environment created by colliding heavy ions.Comment: 4 pages, 3 figures, contribution to the 2019 QCD session of the 54th Rencontres de Morion

Antiparticle to particle ratios and identified hadron spectra in Cu+Cu and Au+Au collisions

New results on antiparticle to particle ratios in Cu+Cu and Au+Au collisions at sqrt(s_NN) = 62.4 and 200 GeV from the PHOBOS experiment at RHIC are presented. Transverse momentum spectra of pions, kaons, protons and antiprotons from Au+Au collisions at sqrt(s_NN) = 62.4 GeV close to mid-rapidity are also discussed. Antiparticle to particle ratios are found to be remarkably independent of the collision centrality in both colliding systems. The collision energy dependence of the pbar/p ratios is very significant in Cu+Cu collisions. Baryons are found to have substantially harder transverse momentum spectra than mesons. The pT region in which the proton to pion ratio reaches unity in central Au+Au collisions at sqrt(s_NN) = 62.4 GeV fits into a smooth trend as a function of collision energy. The observed particle yields at very low pT are comparable to extrapolations from higher pT for kaons, protons and antiprotons. The net proton yield at mid-rapidity is found to be proportional to the number of participant nucleons in Au+Au collisions at 62.4 and 200 GeV energies.Comment: 5 pages, 3 figures, Presented at the Quark Matter 2006 conference in Shanghai, Chin

Az első hadronfizikai mérések a CERN CMS detektorral = The first hadronic physics measurements with the CERN CMS detector

A pályázat keretében a CERN-ben az LHC beindulására készültünk fel, illetve annak első mérési adatait dolgoztuk fel, értékeltük ki és publikáltuk. Ezt a munkát világ egyik legnagyobb tudományos együttműködésében, a CMS kísérletben végeztük. Munkánk számos kutatási területre (a QCD és a Nehézion munkacsoportokban) és a kísérleti munka különböző fázisaira (hardver trigger, szoftver, adatkiértékelés és publikáció) terjedt ki. Megvalósítottuk a CMS kísérletben az inelasztikus ütközéseket nagy hatásfokkal érzékelő rendszert háromféle detektorral. Több algoritmust is kifejlesztettünk az ütközési pont meghatározására. Valós idejű eseményválogatást dolgoztunk ki a keletkezett részecskék száma illetve a detektorban általuk okozott jelek alapján. Javítottunk a részecskepálya-rekonstrukció hatásfokán és kibővítettük az általa lefedett impulzustartományt. A világon először megmértük és publikáltuk a proton-proton ütközésekben keletkezett töltött részecskék szög- és impulzuseloszlását a jelenlegi világrekord 2,36 TeV energián. Kidolgoztuk a töltött részecskékre bomló semleges részecskék mérési módszerét. Eredményeinket a CMS első publikációján kívül kilenc nemzetközi konferencián és öt magyar nyelvű előadásban, valamint 47 kísérleten belül tartott előadásban ismertettük. Munkánk elismeréseként vezető szerepet kaptunk a CMS kísérlet QCD fizikai programjának irányításában. | Using the research grant, we prepared for the startup of the LHC at CERN. We have processed the first experimental data and published the results of the CMS experiment - one of the world's largest scientific collaborations. Our work extended to various scientific subfields (in the QCD and Heavy Ion groups) and to different phases of the experimental work (hardware trigger, software, data mining and publication). We have prepared triggers for the CMS experiment that are sensitive to inelastic collisions with a large efficiency, using three different detectors. We have developed algorithms to determine the position of the collision point. We have designed on-line triggers based on the number of created particles and on the signals in the tracking system created by them. We have improved the efficiency of the track reconstruction and extended the transverse momentum range covered. We have measured, for the first time, the angular and transverse momentum distributions of charged particles created in the p+p collisions at the highest collision energy ever reached in the laboratory (2.36 TeV). We worked on the reconstruction method of neutral particles based on their charged decay products. We have presented our results in the first publication of the CMS experiment on collision data, on nine international conferences and five Hungarian talks and seminars, and in 47 talks given within the CMS experiment. We have been awarded leadership role in the QCD physics group of CMS

Nagy transzverzális impulzusú részecskék fizikája a RHIC és LHC gyorsítókon = Physics of particles with high transverse momentum at the RHIC and LHC accelerators

A kutatást kísérleti részecske- és magfizika témakörben végeztem a RHIC részecskegyorsító PHOBOS illetve az LHC gyorsító CMS kísérletében. A PHOBOS kísérlet nehézion-ütközéseiben előállított, atommagnál sokszorta sűrűbb anyag vizsgálatát segítette elő a különböző tömegű atommagok különböző energiájú ütközéseiben keletkezett nagy transzverzális impulzusú részecskék mennyiségének összehasonlítása. Sokféle szabályosságot, skálázási és univerzalitási tulajdonságot találtunk az adatokban. Ezeket a vizsgálatokat azonosított részecskékkel is elvégeztem. Ehhez kifejlesztettem a repülési időn és az energiaveszteségen alapuló technikák pontosítását és együttes használatát. Megfigyeltem skálázási tulajdonságokat a d+Au ütközésekben mért spektrumokban, és azok sérülését Au+Au ütközésekben. Kollégáimmal kimutattam, hogy nagyon sok részecske-keltési eredmény meglepően egyszerűen következik az ütköző atommagok átfedő tartományának geometriai tulajdonságaiból, pl. pszeudorapiditás-eloszlások, elliptikus folyás illetve annak fluktuációi tekintetében. Foglalkoztam a nagy transzverzális impulzusú részecskék és az ütközésben keletkezett többi részecske közötti korrelációk vizsgálatával. A CMS kísérletben szimulációk segítségével előkészületeket tettem a jet-ekkel kapcsolatos adatkiértékelésre, valamint az első publikációkra a részecske-eloszlások témakörében. Eredményeimet 32 írásos munkában és folyóirat-cikkben közöltem. 31 előadást tartottam a témában, ezek közül 18-at nemzetközi konferencián. | I conducted my research in the field of experimental particle and nuclear physics with the PHOBOS experiment at the RHIC, and with the CMS experiment at the LHC accelerators. The comparison of the yield of particles with high transverse momentum created at various energies in collisions of heavy ions of various mass numbers helped the examination of the medium - much denser than a nucleus - created in these collisions at PHOBOS. Numerous regularities, scaling and universal features have been found in the data. I have also conducted these measurements with identified particles. To do that, I have developed methods to refine and combine the techniques based on time of flight and on specific energy loss. I have observed certain scaling features in d+Au spectra, and their breakdown in Au+Au collisions. We have shown that many features of the data on particle production simply follows from the geometrical features of the overlap zone between colliding nuclei, e.g. concerning pseudorapidity distributions, elliptic flow and its fluctuations. I have studied correlations between high transverse momentum particles and other particles created in the same collision. In the CMS experiment, I have made preparations for data analysis related to jets using computer simulations, and for the first publications concerning particle distributions. These results have been published in 32 written documents and journal articles. I have given 31 talks, 18 of them on international conferences

Simulation of Jet Quenching Observables in Heavy Ion Collisions at the LHC

Large transverse momentum jets provide unique tools to study dense QCD matter in high-energy heavy-ion collisions. Results from RHIC on suppression of high transverse momentum particles in Au+Au collisions indicate a significant energy loss of leading partons in the dense and strongly interacting matter formed in these collisions. The LHC will collide Pb ions at sqrt(s_NN)=5500 GeV, where the cross section of hard scattering will increase dramatically. Large production rates, the large acceptance of the CMS calorimeters and tracking system, combined with the capability of triggering on jets, will extend the transverse momentum reach of charged particle spectra and nuclear modification factors up to p_T>200 GeV/c.Comment: 6 pages, 5 figures. Presented at the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (QM2006), Shanghai, China, November 14-20, 2006. [Grant numbers added in the acknowledgment.

Feasibility Studies of Charge Exchange Measurements in pp Collisions at the LHC

(1) Pions produced in the development of extended atmospheric cosmic ray air showers subsequently decay to muons. The measured yield of those muons is generally underestimated by current phenomenological models and event generators optimized for cosmic ray physics. The importance of those disagreements motivates the feasibility studies for testing these models at the Large Hadron Collider (LHC) energies, at the highest center-of-mass energies achievable in a laboratory. The interaction of a nucleus and a virtual pion created in a charge exchange reaction at the LHC is a similar process to those contributing to the development of air showers in case of cosmic rays. The crucial problem of such an analysis is the selection of charge exchange events with the highest possible efficiency and high purity from proton–proton collisions at the LHC. (2) For this we consider distributions of various measurable quantities given by event generators commonly used in cosmic ray physics. (3) We examine the expected distributions of energy deposited in different calorimeters of an LHC experiment. We consider the geometrical acceptance and energy resolution of the detectors at the Compact Muon Solenoid (CMS) experiment, as an example. We determine a working point cut from the various options for event selection, and compare signal and background predictions using different models for a representative simple observable, such as average transverse momentum or charge particle yield. (4) A set of event selection cuts along these considerations is proposed, with the aim of achieving optimal efficiency and purity

Neutron-gazdag atommagok Coulomb-felbomlási folyamatai dinamikájának vizsgálata = Investigation of the dynamics of Coulomb-breakup of neutron-rich nuclei

A kutatómunka egy megfelelően kiválasztott magreakció vizsgálatának segítségével kívánt következtetni a neutron-gazdag atommagok Coulomb-felbomlási folyamatainak részleteire. A Michigan-i Állami Egyetemen lévő Nemzeti Szupravezető Ciklotron Laboratórium K-1200 gyorsítója mellett kísérletet hajtottunk végre 70 és 40 MeV/u energiájú radioaktív 8Li nyalábbal ólom és szén céltárgyakon, amelyben a bombázó részecske 7Li-re és neutronra való felbomlását figyeltük meg. A 7Li fragmentumot mágnessel térítettük az erre a célra kifejlesztett iondetektor-rendszerbe, a neutronokat a repülési-idő technikával detektáltuk. A több bonyolult részfeladat megoldása után minden megfigyelt bomlásra meghatároztuk a felbomló 8Li izotóp, valamint a felhasadáskor keletkezett neutron és 7Li ion impulzusát. A szén targeten végrehajtott kísérlet lehetővé tette, hogy a Coulomb- és a nukleáris felbomlást mindkét bombázó energiánál az ólomtargettel mért adatoknál elválasszuk. Az eredményekből a 8Li Coulomb-felbomlása hatáskeresztmetszetét meghatároztuk a bomlási energia függvényében. Az előzetes eredmények szerint a 8Li felbomlási hatáskeresztmetszete összhangban van a 7Li(n,?)8Li inverz reakció korábban kísérletileg meghatározott hatáskeresztmetszetével. Kísérleti eredményeink lehetővé teszik a 8Li Coulomb-felbomlásának ütközési paraméter szerinti vizsgálatát és a felbomlási folyamatoknak a két különböző bombázó energiánál való összehasonlítását. Az eredmények véglegesítése és publikálása folyamatban van. | The research work focused on the details of Coulomb-breakup processes of neutron-rich nuclei by means of the investigation of a selected nuclear reaction. Experiments have been performed on lead and carbon targets with 8Li beams of 70 and 40 MeV/u energies at the K-1200 cyclotron of NSCL at Michigan State University. The breakup of 8Li ions into neutrons and 7Li ions was observed. The 7Li fragments were deflected by a sweeper magnet into a detector system. The neutrons from the breakup processes were detected by time-of-flight technique. The evaluation of the experimental data required the development of several sophisticated methods. In the analysis of the data the momenta of the incoming 8Li ion and that of both decay products, the 7Li and the neutron were determined for each detected event. The use of the data for the carbon target made it possible to separate the Coulomb and nuclear part of the decay in the case of the lead target. The cross sections for the neutron breakup of 8Li were determined as the function of the decay energy. According to the preliminary results, the breakup cross section of 8Li is in accordance with the experimentally determined cross section of the inverse reaction 7Li(n,?)8Li. The results of the measurements make it possible to investigate the Coulomb-breakup of 8Li as a function of the impact parameter and the comparison of the breakup processes at the two bombarding energy. The publications of the results are in progress

Hadronfizika a CMS detektorral = Hadronic physics at the CMS experiment

A CERN CMS kísérletében kifejlesztettük a töltött részecskék nyomkövetésének kis tévesztésű, nagyon kis impulzus esetén is jó hatásfokú módszerét. A szilíciumdetektorokban leadott energia, valamint a bomlási topológia figyelembe vételével kidolgoztuk a töltött és semleges részecskék azonosításának technikáját. Megmutattuk, hogy új matematikai eszközökkel a semleges pionok spektruma az egyfoton eloszlásból visszafejthető. A fenti eszközök segítségével elkészítettük a 0.9-7-10 TeV-es proton-proton ütközésekben keletkezett hadronok számával és eloszlásával foglalkozó példa-analíziseket, melyek a 2009-es év végén a CMS kísérlet első publikációi lesznek. A Pb-Pb ütközésben keletkezett anyagon áthaladó partonok energiaveszteségének vizsgálatához kidolgoztuk a nukleáris elnyomási faktorok mérésének módszerét, nagy transzverzális impulzusokra, amely csak jet triggerek alkalmazásával érhető el. A módszerrel várhatóan többszörösére nő majd az az impulzustartomány, ahol a mérés elvégezhető. Létrehoztunk egy megbízható, szcintillátorokon alapuló triggert, amely az első nehézion mérések alapvető triggere lehet 2010-ben. | Working in the CERN CMS experiment we have developed a new method of charged particle tracking that has good efficiency even at very low momentum. With help of the measured energy deposited in the silicon detectors, as well as by using the decay topology, we have worked out a technique of particle identification of charged and neutral hadrons. We have shown that with new mathematical methods the spectrum of neutral pions can be extracted from that of the photons. The above mentioned tools enabled us to prepare and accomplish the example analyses dealing with the measurement of the number distribution and momentum spectrum of hadrons produced in proton-proton collisions at 0.9-7-10 TeV. They will be the first publications of the CMS Collaboration at the end of 2009. For the study of energy loss of partons produced in Pb-Pb collisions, we have developed a method to measure the nuclear modification factors, for high transverse momenta. It was possible with help of jet triggers which multipled the reach of the measurement. We have created a reliable, scintillator based trigger, that can be a basic trigger for the first heavy ion collisions in 2010

Haptoglobin Polymorphism: A Novel Genetic Risk Factor for Celiac Disease Development and Its Clinical Manifestations

Background: Haptoglobin (Hp) α-chain alleles 1 and 2 account for 3 phenotypes that may influence the course of inflammatory diseases via biologically important differences in their antioxidant, scavenging, and immunomodulatory properties. Hp1-1 genotype results in the production of small dimeric, Hp2-1 linear, and Hp2-2 cyclic polymeric haptoglobin molecules. We investigated the haptoglobin polymorphism in patients with celiac disease and its possible association to the presenting symptoms. Methods: We studied 712 unrelated, biopsy-proven Hungarian celiac patients (357 children, 355 adults; severe malabsorption 32.9%, minor gastrointestinal symptoms 22.8%, iron deficiency anemia 9.4%, dermatitis herpetiformis 15.6%, silent disease 7.2%, other 12.1%) and 384 healthy subjects. We determined haptoglobin phenotypes by gel electrophoresis and assigned corresponding genotypes. Results: Hp2-1 was associated with a significant risk for celiac disease (P = 0.0006, odds ratio [OR] 1.54, 95% CI 1.20–1.98; prevalence 56.9% in patients vs 46.1% in controls). It was also overrepresented among patients with mild symptoms (69.2%) or silent disease (72.5%). Hp2-2 was less frequent in patients than in controls (P = 0.0023), but patients having this phenotype were at an increased risk for severe malabsorption (OR 2.21, 95% CI 1.60–3.07) and accounted for 45.3% of all malabsorption cases. Celiac and dermatitis herpetiformis patients showed similar haptoglobin phenotype distributions. Conclusions: The haptoglobin polymorphism is associated with susceptibility to celiac disease and its clinical presentations. The predominant genotype in the celiac population was Hp2-1, but Hp2-2 predisposed to a more severe clinical course. The phenotype-dependent effect of haptoglobin may result from the molecule’s structural and functional properties

Anti-microbial antibodies in celiac disease: trick or treat?

AIM: To determine the prevalence of a new set of anti-glycan and anti-outer membrane protein (anti-OMP) antibodies in a Hungarian cohort of adult Celiac disease (CD) patients. METHODS: 190 consecutive CD patients [M/F: 71/119, age:39.9 (SD:14.1) years], 100 healthy, and 48 gastrointestinal controls were tested for glycan anti-Saccharomyces cerevisiae (gASCA), anti-laminaribioside (ALCA), anti-chitobioside, anti-mannobioside, anti-OMP antibodies and major NOD2/CARD15 mutations. Thirty out of 82 CD patients enrolled at the time of diagnosis were re-evaluated for the same antibodies after longstanding gluten-free diet (GFD). RESULTS: 65.9% of the CD patients were positive for at least one of the tested antibodies at the time of the diagnosis. Except anti-OMP and ALCA, anti-microbial antibodies were exclusively seen in untreated CD; however, the overall sensitivity was low. Any glycan positivity (LR+: 3.13; 95% CI: 2.08-4.73) was associated with an increased likelihood ratio for diagnosing CD. Significant correlation was found between the levels of anti-glycan and anti-endomysial or anti-transglutaminase antibodies. Anti-glycan positivity was lost after longstanding GFD. Anti-glycan antibody titers were associated with symptoms at presentation, but not the presence of NOD2/CARD15 mutations. Patients with severe malabsorption more frequently had multiple antibodies at diagnosis (P = 0.019). CONCLUSION: The presence of anti-glycan antibodies in CD seems to be secondary to the impaired small bowel mucosa which can lead to increased antigen presentation. Furthermore, anti-glycan positivity may be considered an additional marker of CD and dietary adherence