4,460 research outputs found

    A Linear Iterative Unfolding Method

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    A frequently faced task in experimental physics is to measure the probability distribution of some quantity. Often this quantity to be measured is smeared by a non-ideal detector response or by some physical process. The procedure of removing this smearing effect from the measured distribution is called unfolding, and is a delicate problem in signal processing, due to the well-known numerical ill behavior of this task. Various methods were invented which, given some assumptions on the initial probability distribution, try to regularize the unfolding problem. Most of these methods definitely introduce bias into the estimate of the initial probability distribution. We propose a linear iterative method, which has the advantage that no assumptions on the initial probability distribution is needed, and the only regularization parameter is the stopping order of the iteration, which can be used to choose the best compromise between the introduced bias and the propagated statistical and systematic errors. The method is consistent: "binwise" convergence to the initial probability distribution is proved in absence of measurement errors under a quite general condition on the response function. This condition holds for practical applications such as convolutions, calorimeter response functions, momentum reconstruction response functions based on tracking in magnetic field etc. In presence of measurement errors, explicit formulae for the propagation of the three important error terms is provided: bias error, statistical error, and systematic error. A trade-off between these three error terms can be used to define an optimal iteration stopping criterion, and the errors can be estimated there. We provide a numerical C library for the implementation of the method, which incorporates automatic statistical error propagation as well.Comment: Proceedings of ACAT-2011 conference (Uxbridge, United Kingdom), 9 pages, 5 figures, changes of corrigendum include

    10 Years of Object-Oriented Analysis on H1

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    Over a decade ago, the H1 Collaboration decided to embrace the object-oriented paradigm and completely redesign its data analysis model and data storage format. The event data model, based on the RooT framework, consists of three layers - tracks and calorimeter clusters, identified particles and finally event summary data - with a singleton class providing unified access. This original solution was then augmented with a fourth layer containing user-defined objects. This contribution will summarise the history of the solutions used, from modifications to the original design, to the evolution of the high-level end-user analysis object framework which is used by H1 today. Several important issues are addressed - the portability of expert knowledge to increase the efficiency of data analysis, the flexibility of the framework to incorporate new analyses, the performance and ease of use, and lessons learned for future projects.Comment: 14th International Workshop on Advanced Computing and Analysis Techniques in Physics Researc

    Signals of Disoriented Chiral Condensate

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    If a disoriented chiral condensate is created over an extended space-time region following a rapid cooling in hadronic or nuclear collisions, the misalignment of the condensate with the electroweak symmetry breaking can generate observable effects in the processes which involve both strong and electromagnetic interactions. We point out the relevance of the dilepton decay of light vector mesons as a signal for formation of the disoriented condensate. We predict that the decay \rho^0 to dileptons will be suppressed and/or the \rho resonance peak widens, while the decay \omega to dileptons will not be affected by the condensate.Comment: 13 pages in LaTeX, UCB-PTH-94/05, LBL-3533

    Validation of Kalman Filter alignment algorithm with cosmic-ray data using a CMS silicon strip tracker endcap

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    A Kalman Filter alignment algorithm has been applied to cosmic-ray data. We discuss the alignment algorithm and an experiment-independent implementation including outlier rejection and treatment of weakly determined parameters. Using this implementation, the algorithm has been applied to data recorded with one CMS silicon tracker endcap. Results are compared to both photogrammetry measurements and data obtained from a dedicated hardware alignment system, and good agreement is observed.Comment: 11 pages, 8 figures. CMS NOTE-2010/00

    EU-Funded Telemedicine Projects 鈥 Assessment of, and Lessons Learned From, in the Light of the SARS-CoV-2 Pandemic

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    The SARS-CoV-2 health emergency has demonstrated the need for developing structured telemedicine systems to protect citizens from the spread of the virus. Thereby, their importance and the necessity to tailor their diffusion at large scale for providing services both at a distance and in time has been shown. For these reasons, the European Union advocates the digital transition of health systems for the next 5 years. The main aim of this work is to revisit the telemedicine research projects financed by European Community during the period 2000-2020 with particular respect to the results derived from their application. The analysis showed that some integration of tele-care and tele-health could be obtained with tele-monitoring systems and the implementation of Electronic Personal Record (EPR). Furthermore, telemedicine allows enhancing health care in critical environments, to protect health and life of the most vulnerable patients, and to encourage cross-border dialogue. The criteria of 鈥渇rom distance鈥 and 鈥渢imely delivered鈥 are granted, but the effectiveness of the overall offered services highly depends on the availability and the quality of the input data. Unfortunately, this remains a relevant problem in the SARS-CoV-2 pandemic

    鏂板弾浣滃搧 : 銈搞儳銉偢銉ャ兓銉夈兓銉┿兓銉堛偉銉笺儷銆婅仏銉堛優銈广

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    We present a tomographic technique making use of a gigaelectronvolt electron beam for the determination of the material budget distribution of centimeter-sized objects by means of simulations and measurements. In both cases, the trajectory of electrons traversing a sample under test is reconstructed using a pixel beam-telescope. The width of the deflection angle distribution of electrons undergoing multiple Coulomb scattering at the sample is estimated. Basing the sinogram on position-resolved estimators enables the reconstruction of the original sample using an inverse radon transform. We exemplify the feasibility of this tomographic technique via simulations of two structured cubes鈥攎ade of aluminium and lead鈥攁nd via an in-beam measured coaxial adapter. The simulations yield images with FWHM edge resolutions of (177鈥壜扁13)鈥壩糾 and a contrast-to-noise ratio of 5.6鈥壜扁0.2 (7.8鈥壜扁0.3) for aluminium (lead) compared to air. The tomographic reconstruction of a coaxial adapter serves as experimental evidence of the technique and yields a contrast-to-noise ratio of 15.3鈥壜扁1.0 and a FWHM edge resolution of (117鈥壜扁4)鈥壩糾

    Charged-Particle Multiplicity in Proton-Proton Collisions

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    This article summarizes and critically reviews measurements of charged-particle multiplicity distributions and pseudorapidity densities in p+p(pbar) collisions between sqrt(s) = 23.6 GeV and sqrt(s) = 1.8 TeV. Related theoretical concepts are briefly introduced. Moments of multiplicity distributions are presented as a function of sqrt(s). Feynman scaling, KNO scaling, as well as the description of multiplicity distributions with a single negative binomial distribution and with combinations of two or more negative binomial distributions are discussed. Moreover, similarities between the energy dependence of charged-particle multiplicities in p+p(pbar) and e+e- collisions are studied. Finally, various predictions for pseudorapidity densities, average multiplicities in full phase space, and multiplicity distributions of charged particles in p+p(pbar) collisions at the LHC energies of sqrt(s) = 7 TeV, 10 TeV, and 14 TeV are summarized and compared.Comment: Invited review for Journal of Physics G -- version 2: version after referee's comment

    (770)0\rho(770)^0, K(892)0^*(892)^0 and f0(980)_{0}(980) Production in Au-Au and pp Collisions at sNN\sqrt{s_{NN}} = 200 GeV

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    Preliminary results on (770)0+\rho(770)^0 \to \pi^{+}\pi^{-}, K(892)0^{*}(892)^{0} \to \piK and f0(980)+f_{0}(980) \to \pi^{+}\pi^{-} production using the mixed-event technique are presented. The measurements are performed at mid-rapidity by the STAR detector in sNN\sqrt{s_{NN}}= 200 GeV Au-Au and pp interactions at RHIC. The results are compared to different measurements at various energies.Comment: 4 pages, 6 figures. Talk presented at Quark Matter 2002, Nantes, France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A

    The directed flow maximum near c_s=0

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    We investigate the excitation function of quark-gluon plasma formation and of directed in-plane flow of nucleons in the energy range of the BNL-AGS and for the E(Lab)=40AGeV Pb+Pb collisions performed recently at the CERN-SPS. We employ the three-fluid model with dynamical unification of kinetically equilibrated fluid elements. Within our model with first-order phase transition at high density, droplets of QGP coexisting with hadronic matter are produced already at BNL-AGS energies, E(Lab)=10AGeV. A substantial decrease of the isentropic velocity of sound, however, requires higher energies, E(Lab)=40AGeV. We show the effect on the flow of nucleons in the reaction plane. According to our model calculations, kinematic requirements and EoS effects work hand-in-hand at E(Lab)=40AGeV to allow the observation of the dropping velocity of sound via an increase of the directed flow around midrapidity as compared to top BNL-AGS energy.Comment: 10 pages, 4 figures; plot of p(e) at various specific entropies shows why mixed phase is not soft at AGS energ

    J/Psi Suppression in Heavy Ion Collisions at the CERN SPS

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    We reexamine the production of J/Psi and other charmonium states for a variety of target-projectile choices at the SPS. For this study we use a newly constructed cascade code LUCIFER II, which yields acceptable descriptions of both hard and soft processes, specifically Drell-Yan and hidden charm production, and soft energy loss and meson production, at the SPS. Glauber calculations of other authors are redone, and compared directly to the cascade results. The modeling of the charmonium states differs from that of earlier workers in its unified treatment of the hidden charm meson spectrum, which is introduced from the outset as a set of coupled states. The result is a description of the NA38 and NA50 data in terms of a conventional hadronic picture. The apparently anomalous suppression found in the most massive Pb+Pb system arises from three sources: destruction in the initial nucleon-nucleon cascade, use of coupled channels to exploit the larger breakup in the less bound Chi and Psi' states, and comover interaction in the final low energy phase.Comment: 36 pages (15 figures
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