Three-jet angular correlations and subjet distributions at ZEUS

Besides structure function measurements and jet physics, there is a lively collection of more specific QCD analyses at HERA. In this contribution we present three-jet angular correlations and subjet distributions measured in ep collisions with the ZEUS detector. The angular correlations provide sensitivity to the color factors of the underlying gauge group and thus facilitate tests of basic properties of the strong interaction. The subjet distributions allow tests of the QCD radiation pattern within a jet in the perturbative regime.Comment: 4 pages, 2 figures, talk given on behalf of the ZEUS collaboration at DIS06, Tsukuba, Japan, April 200

Measurement of angular correlations of jets at sqrt(s)=1.96 TeV and determination of the strong coupling at high momentum transfers

We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance Delta-R in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of Delta-R and for different transverse momentum requirements for the neighboring jets. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider in pp-bar collisions at sqrt(s)=1.96 The results are well described by a perturbative QCD calculation in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects. From these results, we extract the strong coupling and test the QCD predictions for its running over a range of momentum transfers of 50-400 GeV.Comment: 10 pages, 3 figures, 3 tables; v2 as published in Phys. Lett.

Observation of the decay hc→3(π+π−)π0h_{c}\to3(\pi^{+}\pi^{-})\pi^{0}

Based on $(2712.4\pm14.1)\times10^{6}$ $\psi(3686)$ events collected with the BESIII detector, we study the decays $h_{c}\to3(\pi^{+}\pi^{-})\pi^{0}$, $h_{c}\to2(\pi^{+}\pi^{-})\omega$, $h_{c}\to2(\pi^{+}\pi^{-})\pi^{0}\eta$, $h_{c}\to2(\pi^{+}\pi^{-})\eta$, and $h_{c}\to p\bar{p}$ via $\psi(3686)\to\pi^{0}h_{c}$. The decay channel $h_{c}\to3(\pi^{+}\pi^{-})\pi^{0}$ is observed for the first time, and its branching fraction is determined to be $\left( {9.28\pm 1.14 \pm 0.77} \right) \times {10^{ - 3}}$, where the first uncertainty is statistical and the second is systematic. In addition, first evidence is found for the modes $h_{c} \to 2(\pi^{+}\pi^{-})\pi^{0}\eta$ and $h_{c}\to2(\pi^{+}\pi^{-})\omega$ with significances of 4.8$\sigma$ and 4.7$\sigma$, and their branching fractions are determined to be $(7.55\pm1.51\pm0.77)\times10^{-3}$ and $\left( {4.00 \pm 0.86 \pm 0.35}\right) \times {10^{ - 3}}$, respectively. No significant signals of $h_c\to 2(\pi^+\pi^-)\eta$ and $h_{c}\to p\bar{p}$ are observed, and the upper limits of the branching fractions of these decays are determined to be $<6.19\times10^{-4}$ and $<4.40\times10^{-5}$ at the 90% confidence level, respectively.Comment: 11 pages, 3 figure

Measurement of angular correlations of jets at root s=1.96 TeV and determination of the strong coupling at high momentum transfers

We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance �R in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of �R and for different transverse momentum requirements for the neighboring jets. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb−1 collected with the D0 detector at the Fermilab Tevatron Collider in p¯p collisions at √ s = 1.96 TeV. The results are well described by a perturbative QCD calculation in next-toleading order in the strong coupling constant, corrected for non-perturbative effects. From these results, we extract the strong coupling and test the QCD predictions for its running over a range of momentum transfers of 50–400 GeV

High Performance Numerical Computing for High Energy Physics: A New Challenge for Big Data Science

The publication of this article was funded by SCOAP 3 . Modern physics is based on both theoretical analysis and experimental validation. Complex scenarios like subatomic dimensions, high energy, and lower absolute temperature are frontiers for many theoretical models. Simulation with stable numerical methods represents an excellent instrument for high accuracy analysis, experimental validation, and visualization. High performance computing support offers possibility to make simulations at large scale, in parallel, but the volume of data generated by these experiments creates a new challenge for Big Data Science. This paper presents existing computational methods for high energy physics (HEP) analyzed from two perspectives: numerical methods and high performance computing. The computational methods presented are Monte Carlo methods and simulations of HEP processes, Markovian Monte Carlo, unfolding methods in particle physics, kernel estimation in HEP, and Random Matrix Theory used in analysis of particles spectrum. All of these methods produce data-intensive applications, which introduce new challenges and requirements for ICT systems architecture, programming paradigms, and storage capabilities

High Performance Numerical Computing for High Energy Physics: A New Challenge for Big Data Science

Modern physics is based on both theoretical analysis and experimental validation. Complex scenarios like subatomic dimensions, high energy, and lower absolute temperature are frontiers for many theoretical models. Simulation with stable numerical methods represents an excellent instrument for high accuracy analysis, experimental validation, and visualization. High performance computing support offers possibility to make simulations at large scale, in parallel, but the volume of data generated by these experiments creates a new challenge for Big Data Science. This paper presents existing computational methods for high energy physics (HEP) analyzed from two perspectives: numerical methods and high performance computing. The computational methods presented are Monte Carlo methods and simulations of HEP processes, Markovian Monte Carlo, unfolding methods in particle physics, kernel estimation in HEP, and Random Matrix Theory used in analysis of particles spectrum. All of these methods produce data-intensive applications, which introduce new challenges and requirements for ICT systems architecture, programming paradigms, and storage capabilities

Measurement of the decay η′ →π0π0η at MAMI

An experimental study of the η′→π0π0η→6γ decay has been conducted with the best up-to-date statistical accuracy, by measuring η′ mesons produced in the γp→η′p reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The results obtained for the standard parametrization of the η′→π0π0η matrix element are consistent with the most recent results for η′→ππη decays, but have smaller uncertainties. The available statistics and experimental resolution allowed, for the first time, an observation of a structure below the π+π- mass threshold, the magnitude and sign of which, checked within the framework of the nonrelativistic effective-field theory, demonstrated good agreement with the cusp that was predicted based on the ππ scattering length combination, a0-a2, extracted from K→3π decays