Topological Cuts Research Articles

Radiogenic backgrounds in the NEXT double beta decay experiment

Natural radioactivity represents one of the main backgrounds in the search for neutrinoless double beta decay. Within the NEXT physics program, the radioactivity- induced backgrounds are measured with the NEXT-White detector. Data from 37.9 days of low-background operations at the Laboratorio Subterráneo de Canfranc with xenon depleted in 136Xe are analyzed to derive a total background rate of (0.84±0.02) mHz above 1000 keV. The comparison of data samples with and without the use of the radon abatement system demonstrates that the contribution of airborne-Rn is negligible. A radiogenic background model is built upon the extensive radiopurity screening campaign conducted by the NEXT collaboration. A spectral fit to this model yields the specific contributions of 60Co, 40K, 214Bi and 208Tl to the total background rate, as well as their location in the detector volumes. The results are used to evaluate the impact of the radiogenic backgrounds in the double beta decay analyses, after the application of topological cuts that reduce the total rate to (0.25±0.01) mHz. Based on the best-fit background model, the NEXT-White median sensitivity to the two-neutrino double beta decay is found to be 3.5σ after 1 year of data taking. The background measurement in a Qββ±100 keV energy window validates the best-fit background model also for the neutrinoless double beta decay search with NEXT-100. Only one event is found, while the model expectation is (0.75±0.12) events.

Cast shadow detection based on the YCbCr color space and topological cuts

In order to solve the moving objects shadow problem in foreground extraction of surveillance video images, a new cast shadow detection algorithm based on the YCbCr color space and topological cutting was proposed. Preliminary shadow removal was first performed based on the difference of the three components in the YCbCr color space of shadows and foregrounds. Besides, the maximum-flow/minimum-cut algorithm for image segmentation was optimized considering the topological constraints. The optimal segmentation of the foreground image was obtained during the continuous updating of the label. Finally, two sets of experiments were performed in video image sequences, including real surveillance videos and a well-known benchmark test set. By comparing with two other existing algorithms, the feasibility and effectiveness of the cast shadow detection algorithm were verified by the smooth border and higher recognition accuracy. In addition, the adaptability to foreground object density and different light intensities was measured in an airport terminal, showing that this algorithm can provide a high quality of moving foreground detection in surveillance video images and can be applied in monitoring of public places.

Exploring the doubly charged Higgs boson of the left-right symmetric model using vector boson fusionlike events at the LHC

This paper studies the pair production of the doubly charged Higgs boson of the left-right symmetric models using multilepton final state in the vector boson fusion (VBF)-like processes. The study is performed in the framework consistent with the model's correction to the standard model $\rho_{EW}$ parameter. VBF topological cuts, number of leptons in the final state and $p_T$ cuts on the leptons are found to be effective in suppressing the background. Significant mass reach can be achieved for exclusion/discovery of the doubly charge Higgs boson for the upcoming LHC run with a luminosity of $\mathcal{O}(10^3)$ fb$^{-1}$.

A plan for directional dark matter sensitivity in high-pressure xenon detectors through the addition of wavelength shifting gaseous molecules

Xenon is an especially attractive candidate for both direct WIMP and 0νββ decay searches. Although the current trend has exploited the liquid phase, the gas phase xenon offers remarkable performance advantages for: energy resolution, topology visualization, and discrimination between electron and nuclear recoils. The NEXT-100 experiment, now under construction in the Canfranc Underground Laboratory, Spain, will operate at ∼ 15 bars with 100 kg of 136Xe for the 0νββ decay search. We will describe recent results with small prototypes, indicating that NEXT-100 can provide about 0.5% FWHM energy resolution at the decay's Q value (2457.83 keV), as well as rejection of γ-rays with topological cuts. However, sensitivity goals for WIMP dark matter and 0νββ decay searches indicate the probable need for ton-scale active masses. NEXT-100 provides the springboard to reach this scale with xenon gas. We describe a scenario for performing both searches in a single, high-pressure, ton-scale xenon gas detector, without significant compromise to either. In addition, even in a single ton-scale, high-pressure xenon gas TPC, an intrinsic sensitivity to the nuclear recoil direction may exist. This plausibly offers an advance of more than two orders of magnitude relative to current low-pressure TPC concepts. We argue that, in an era of deepening fiscal austerity, such a dual-purpose detector may be possible at acceptable cost, within the time frame of interest, and deserves our collective attention.

Numerical evaluation of multi-loop integrals for arbitrary kinematics with SecDec 2.0

We present the program SecDec 2.0, which contains various new features. First, it allows the numerical evaluation of multi-loop integrals with no restriction on the kinematics. Dimensionally regulated ultraviolet and infrared singularities are isolated via sector decomposition, while threshold singularities are handled by a deformation of the integration contour in the complex plane. As an application, we present numerical results for various massive two-loop four-point diagrams. SecDec 2.0 also contains new useful features for the calculation of more general parameter integrals, related for example to phase space integrals. Program summaryProgram title: SecDec 2.0Catalogue identifier: AEIR_v2_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEIR_v2_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 156829No. of bytes in distributed program, including test data, etc.: 2137907Distribution format: tar.gzProgramming language: Wolfram Mathematica, Perl, Fortran/C++.Computer: From a single PC to a cluster, depending on the problem.Operating system: Unix, Linux.RAM: Depending on the complexity of the problemClassification: 4.4, 5, 11.1.Catalogue identifier of previous version: AEIR_v1_0Journal reference of previous version: Comput. Phys. Comm. 182(2011)1566Does the new version supersede the previous version?: YesNature of problem: Extraction of ultraviolet and infrared singularities from parametric integrals appearing in higher order perturbative calculations in gauge theories. Numerical integration in the presence of integrable singularities (e.g., kinematic thresholds).Solution method: Algebraic extraction of singularities in dimensional regularization using iterated sector decomposition. This leads to a Laurent series in the dimensional regularization parameter ϵ, where the coefficients are finite integrals over the unit hypercube. Those integrals are evaluated numerically by Monte Carlo integration. The integrable singularities are handled by choosing a suitable integration contour in the complex plane, in an automated way.Reasons for new version: In the previous version the calculation of multi-scale integrals was restricted to the Euclidean region. Now multi-loop integrals with arbitrary physical kinematics can be evaluated. Another major improvement is the possibility of full parallelization.Summary of revisions:•No restriction on the kinematics for multi-loop integrals.•The integrand can be constructed from the topological cuts of the diagram.•Possibility of full parallelization.•Numerical integration of multi-loop integrals written in C++ rather than Fortran.•Possibility to loop over ranges of parameters.Restrictions: Depending on the complexity of the problem, limited by memory and CPU time. The restriction that multi-scale integrals could only be evaluated at Euclidean points is superseded in version 2.0.Running time: Between a few minutes and several days, depending on the complexity of the problem. Test runs provided take only seconds.

Astrophysical Tau Neutrino Searches with IceCube

IceCube, a cubic kilometer size neutrino telescope operating in the deep ice at the South Pole, has the capability to detect all flavors of neutrinos: νe, νμ and ντ. For the IceCube 22 string (IC22) data we applied some simple topological cuts to identify Ultra High Energy (UHE) tau neutrinos in the energy range from 1 PeV to 1 EeV. These cuts are also sensitive to astrophysical νe and νμ as well as ντ in the final event selection. Thus, here, we present our sensitivity on the astrophysical all flavor neutrino flux for the 200 live days with IC22.

An FPGA based demonstrator for a topological processor in the future ATLAS L1-Calo trigger “GOLD”

The existing ATLAS trigger consists of three levels. The level 1 (L1) is an FPGAs based custom designed trigger, while the second and third levels are software based. The LHC machine plans to bring the beam energy to the maximum value of 7 TeV and to increase the luminosity in the coming years. The current L1 trigger system is therefore seriously challenged. To cope with the resulting higher event rate, as part of the ATLAS trigger upgrade, a new electronics module is foreseen to be added into the ATLAS Level-1 Calorimeter Trigger electronics chain: the topological Processor (TP). Such a processor needs fast optical I/O and large aggregate bandwidth to use the information on trigger object position in space (e.g. jets in the calorimeters or muons measured in the muon detectors) to improve the purity of the L1 triggers streams by applying topological cuts within the L1 latency budget. In this paper, an overview of the adopted technological solutions and the R&}D activities on the demonstrator for the TP (“GOLD”) are presented.

Perspectives for the measurement of D s + mesons via the D s + →K + K − π + channel in the ALICE experiment

Heavy quarks, such as charm, are produced in hard scatterings in the early stages of high energy nucleus-nucleus collisions and are expected to be a powerful tool to investigate the properties of the quark gluon plasma (QGP). The tracking detectors of the ALICE apparatus will allow to track and identify particles in central rapidity range down to low P t . Among D mesons it would be particularly interesting to measure D s yield via an exclusive hadronic decay channel because it could help to disentangle different hadronization mechanisms. The possibility of reconstructing the D s meson through its D s + →K + K − π + decay channel in the central barrel was studied. The problem considered is characterized by the comparatively low yield of the D s mesons against the huge amount of combinatorial background. Different kinematic and topological cuts have been studied in order to increase the signal-to-background ratio and the statistical significance. In addition, D s mesons preferentially decay through intermediate resonant states and this fact can improve the separation of signal from background. Results of cut parameters tuning and values of significance for an analysis performed on simulated data are presented.

Identification of the K*± resonance decay by topological cuts and multivariate discrimination methods

A study of the identification of the short-lived K*± resonance via its decay into a K0s and a charged pion has been carried out. A sample of minimum bias PYTHIA pp collision events has been simulated and fully reconstructed in the ALICE detector. Traditional methods based on multidimensional topological cuts and artificial neural networks with different architectures have been compared in detail. Examples of additional use of multivariate discrimination methods are also reported.

CERES measurement of strangeness production at top SPS energy

A measurement of the K0S yield in central PbAu collisions at top SPS energy is reported. The analysis was performed without topological cuts taking advantage of the large data sample of 30 × 106 events. The obtained rapidity spectrum follows a Gaussian distribution with width σ = 1.3 ± 0.2 and a yield at midrapidity dN/dy = 21.2 ± 0.9stat ± 1.7syst. The rapidity spectrum was compared to measurements by NA49 and NA57 and to calculation of the thermal model. The inverse slope parameter of the transverse momentum distribution equals T = 222 ± 3stat ± 10syst MeV and follows global systematics.

A measurement of the gluon splitting rate into [formula omitted] pairs in hadronic Z decays

A measurement of the fraction of hadronic Z decays in which a gluon splits into a b b ̄ pair, g b b ̄ , is presented using data collected by ALEPH from 1992 to 1995 at the Z resonance. The selection is based on four-jet events. Events are selected by means of topological cuts and a lifetime tag. The result is g b b ̄ =(2.77±0.42 (stat)±0.57 (syst))×10 −3 .

Search for Bc and ϒ in Hadronic Z Decays

Out of 3.9 million hadronic Z decays collected by the ALEPH detector, a sample of approximately 700 J/ψ events decaying into e+ e- or μ+μ- are selected. A search for the Bc meson decaying into the channels J/ψπ+, J/ψe+νe and J/ψμ+νμ is then performed, resulting in the observation of 0, 1 and 1 candidate in each of these channels respectively, with 0.37, 0.28 and 0.36 background events expected. The following 90% confidence level upper limits are derived: [Formula: see text] An intriguing candidate, found in an independent analysis, is also described in detail. Using the same data sample, a search is performed for the ϒ(1S), ϒ(2S) and ϒ(3S) states, decaying into either e+e- or μ+μ-. After kinematic and topological cuts a total of 1.2 ± 0.4 background events are expected for both channels in the mass window chosen. Two events are observed, allowing the following 90% confidence level branching fraction upper limit to be derived: [Formula: see text]

Measurement of the [formula omitted] lifetime

We present the measurement of the lifetime of the Ω c 0 we have performed using three independent data samples from two different decay modes. Using a Σ − beam of 340 GeV c we have obtained clean signals for the Ω c 0 decaying i Ξ − K − π + π + and Ω −π +π −π + , avoiding topological cuts normally used in charm analysis. The short but measurable lifetime of the Ω c 0 is demonstrated by a clear enhancement of the signals at short but finite decay lengths. Using a continuous maximum likelihood method we determined the lifetime to be τ ω c 0 = 55 −11 +13(stat) −23 +18(syst) fs. This makes the Ω c 0 the shortest living weakly decaying particle observed so far. The short value of the lifetime comfirms the predicted pattern of the charmed baryon lifetimes and demonstrates that the strong interaction plays a vital role in the lifetimes of charmed hadrons.

B2-EIRENE simulation of ASDEX and ASDEX-Upgrade scrape-off layer plasmas

The 2D multifluid edge code B2 coupled with the 3D neutral gas Monte Carlo code EIRENE is being used for edge interpretation and model validation on the axisymmetric poloidal divertor experiments ASDEX and ASDEX-Upgrade. For this purpose B2 was significantly improved especially by a fully implicit treatment of the topological cuts appearing in X-point configurations, and a reasonably accurate handling of inclined target plates. A fast, automatic grid generator has been developed, which allows direct implementation of experimental MHD equilibria into B2-EIRENE. Typical ASDEX and ASDEX-Upgrade simulations are presented and discussed.

Multijet cross sections in hadronic collisions.

Multijet events have been extensively studied at the CERN pp-bar collider. The production rates and the topology of the events can be quantitatively understood in the framework of perturbative QCD. There are many ''new physics'' processes for which such multijet events are an important background. We examine several such processes, including Higgs boson, heavy-quark pair, and heavy Z production. In each case we calculate the signal and background rates and investigate the efficacy of topological cuts on the final states. Our results have important consequences for future very-high-energy hadron colliders.