Publications (25)5.72 Total impact
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Article: Model-Independent Identification of Inelastic WIMPs from Direct Dark Matter Detection Experiments
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ABSTRACT: In this article we introduce model-independent data analysis procedures for identifying inelastic WIMP-nucleus scattering as well as for reconstructing the mass and the mass splitting of inelastic WIMPs simultaneously and separately. Our simulations show that, with O(50) observed WIMP signals from one experiment, one could already distinguish the inelastic WIMP scattering scenarios from the elastic one. By combining two or more data sets with positive signals, the WIMP mass and the mass splitting could even be reconstructed with statistical uncertainties of less than a factor of two.03/2013; -
Article: Background effects on reconstructed WIMP couplings
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ABSTRACT: In this talk, I presented effects of small, but non-negligible unrejected background events on the determinations of WIMP couplings/cross sections.01/2012; -
Article: Analyzing direct dark matter detection data with unrejected background events by the AMIDAS website
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ABSTRACT: In this talk I have presented the data analysis results of extracting properties of halo WIMPs: the mass and the (ratios between the) spin-independent and spin-dependent couplings/cross sections on nucleons by the AMIDAS website by taking into account possible unrejected background events in the analyzed data sets. Although non-standard astronomical setup has been used to generate pseudodata sets for our analyses, it has been found that, without prior information/assumption about the local density and velocity distribution of halo Dark Matter, these WIMP properties have been reconstructed with ~ 2% to <~ 30% deviations from the input values.11/2011; -
Article: Effects of Residue Background Events in Direct Dark Matter Detection Experiments on the Determinations of Ratios of WIMP-Nucleon Cross Sections
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ABSTRACT: In our work on the development of model-independent data analysis methods for determining ratios between different couplings/cross sections of Weakly Interacting Massive Particles (WIMPs) by using measured recoil energies from direct Dark Matter detection experiments directly, it was assumed that the analyzed data sets are background-free, i.e., all events are WIMP signals. In this article, as a more realistic study, we take into account a fraction of possible residue background events, which pass all discrimination criteria and then mix with other real WIMP-induced events in our data sets. Our simulations show that, assuming that the spin-dependent (SD) WIMP-nucleus interaction dominates over the spin-independent (SI) one, the maximal acceptable fraction of residue background events in the analyzed data sets for determining the ratio of the SD WIMP coupling on neutrons to that on protons is ~ 20% - 40%; whereas considering a general combination of the SI and SD WIMP interactions, the maximal acceptable background ratio for determining the ratio between two SD WIMP couplings as well as the ratios of the SD cross section on protons (neutrons) to the SI one is ~ 10% - 20%. Moreover, by considering different forms of background spectrum, we find that only background events in the lowest energy ranges could affect the reconstructions (significantly); those in high energy ranges would almost not change the reconstructed ratios or only very slightly.04/2011; -
Article: Effects of Residue Background Events in Direct Dark Matter Detection Experiments on the Estimation of the Spin-Independent WIMP-Nucleon Coupling
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ABSTRACT: In our work on the development of a model-independent data analysis method for estimating the spin-independent (SI) scalar coupling of Weakly Interacting Massive Particles (WIMPs) on nucleons by using measured recoil energies from direct Dark Matter detection experiments directly, it was assumed that the analyzed data sets are background-free, i.e., all events are WIMP signals. In this article, as a more realistic study, we take into account a fraction of possible residue background events, which pass all discrimination criteria and then mix with other real WIMP-induced events in our data sets. Our simulations show that, for the estimation of the SI WIMP-nucleon coupling, the maximal acceptable fraction of residue background events in the analyzed data set of O(50) total events is ~ 10% - 20%. For a WIMP mass of 100 GeV and 20% residue background events, the systematic deviation of the reconstructed SI WIMP coupling (with a reconstructed WIMP mass) would in principle be ~ +13% with a statistical uncertainty of ~ ^{+21%}_{-14%} (~ -3.3%^{+18%}_{-13%} for background-free data sets).03/2011; -
Article: Estimating the Spin-Independent WIMP-Nucleon Coupling from Direct Dark Matter Detection Data
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ABSTRACT: Weakly Interacting Massive Particles (WIMPs) are one of the leading candidates for Dark Matter. For understanding the nature of WIMPs and identifying them among new particles produced at colliders (hopefully in the near future), determinations of their mass and couplings on nucleons from direct Dark Matter detection experiments are essential. Based on our model-independent method for determining the WIMP mass from experimental data, I present a way to also estimate the spin-independent (SI) WIMP-nucleon coupling by using measured recoil energies directly. This method is independent of the velocity distribution of halo WIMPs as well as (practically) of the as yet unknown WIMP mass. In a background-free environment, for a WIMP mass of ~ 100 GeV the SI WIMP-nucleon coupling could in principle be estimated with an uncertainty of ~ 15% by using 2 (or 3) x 50 events from experiments.03/2011; -
Article: Determining Ratios of WIMP-Nucleon Cross Sections from Direct Dark Matter Detection Data
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ABSTRACT: Weakly Interacting Massive Particles (WIMPs) are one of the leading candidates for Dark Matter. So far the usual procedure for constraining the WIMP-nucleon cross sections in direct Dark Matter detection experiments have been to fit the predicted event rate based on some model(s) of the Galactic halo and of WIMPs to experimental data. One has to assume whether the spin-independent (SI) or the spin-dependent (SD) WIMP-nucleus interaction dominates, and results of such data analyses are also expressed as functions of the as yet unknown WIMP mass. In this article, I introduce methods for extracting information on the WIMP-nucleon cross sections by considering a general combination of the SI and SD interactions. Neither prior knowledge about the local density and the velocity distribution of halo WIMPs nor about their mass is needed. Assuming that an exponential-like shape of the recoil spectrum is confirmed from experimental data, the required information are only the measured recoil energies (in low energy ranges) and the number of events in the first energy bin from two or more experiments.03/2011; -
Article: Effects of Residue Background Events in Direct Detection Experiments on Identifying WIMP Dark Matter
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ABSTRACT: We reexamine the model-independent data analysis methods for extracting properties of Weakly Interacting Massive Particles (WIMPs) by using data (measured recoil energies) from direct Dark Matter detection experiments directly and, as a more realistic study, consider a small fraction of residue background events, which pass all discrimination criteria and then mix with other real WIMP-induced signals in the analyzed data sets. In this talk, the effects of residue backgrounds on the determination of the WIMP mass as well as the spin-independent WIMP coupling on nucleons will be discussed. Comment: 8 pages, 6 eps figures, to appear in the proceedings of the 2nd International Workshop on Dark Matter, Dark Eaergy, and Matter-Antimatter Asymmetry, Hsinchu, Taiwan, November 5-6, 201012/2010; -
Article: Effects of Residue Background Events in Direct Detection Experiments on Determining Properties of Halo Dark Matter
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ABSTRACT: We reexamine the model-independent data analysis methods for extracting properties of Weakly Interacting Massive Particles (WIMPs) by using data (measured recoil energies) from direct Dark Matter detection experiments directly and, as a more realistic study, consider a small fraction of residue background events, which pass all discrimination criteria and then mix with other real WIMP-induced signals in the analyzed data sets. In this talk, the effects of residue backgrounds on the determination of the mass of halo Dark Matter particle as well as on the reconstruction of its one-dimensional velocity distribution function will be discussed. Comment: 7 pages, 10 eps figures, to appear in the proceedings of Identification of Dark Matter (IDM 2010), Montpellier, France, 26-30 July, 201011/2010; -
Article: Script Handbook for Interactive Scientific Website Building
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ABSTRACT: In this handbook, I collect the basic (and eventually upgraded) PHP scripts used for building the AMIDAS website (http://pisrv0.pit.physik.uni-tuebingen.de/darkmatter/amidas/), an online interactive simulation/data analysis system for direct Dark Matter detection experiments. Some basic, often used commands of (X)HTML, CSS, JavaScript, HTML DOM, and PHP are also given in an appendix. Comment: 205 pages, 48 eps figures; lecture material for NCKU Computation Summer Camp, Tainan, Taiwan, August 9-14, 2010; v2: typos fixed, notes added08/2010; -
Article: Effects of Residue Background Events in Direct Dark Matter Detection Experiments on the Reconstruction of the Velocity Distribution Function of Halo WIMPs
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ABSTRACT: In our earlier work on the development of a model-independent data analysis method for reconstructing the (moments of the) time-averaged one-dimensional velocity distribution function of Weakly Interacting Massive Particles (WIMPs) by using measured recoil energies from direct Dark Matter detection experiments directly, it was assumed that the analyzed data sets are background-free, i.e., all events are WIMP signals. In this article, as a more realistic study, we take into account a fraction of possible residue background events, which pass all discrimination criteria and then mix with other real WIMP-induced events in our data sets. Our simulations show that, for the reconstruction of the one-dimensional WIMP velocity distribution, the maximal acceptable fraction of residue background events in the analyzed data set(s) of O(500) total events is ~10% - 20%. For a WIMP mass of 50 GeV with a negligible uncertainty and 20% residue background events, the deviation of the reconstructed velocity distribution would in principle be ~7.5% with a statistical uncertainty of ~18% (~19% for a background-free data set). Comment: 23 pages, 38 eps figures; v2: revised version for publication, references added and updated03/2010; -
Article: Effects of Residue Background Events in Direct Dark Matter Detection Experiments on the Determination of the WIMP Mass
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ABSTRACT: In the earlier work on the development of a model-independent data analysis method for determining the mass of Weakly Interacting Massive Particles (WIMPs) by using measured recoil energies from direct Dark Matter detection experiments directly, it was assumed that the analyzed data sets are background-free, i.e., all events are WIMP signals. In this article, as a more realistic study, we take into account a fraction of possible residue background events, which pass all discrimination criteria and then mix with other real WIMP-induced events in our data sets. Our simulations show that, for the determination of the WIMP mass, the maximal acceptable fraction of residue background events in the analyzed data sets of O(50) total events is ~20%, for background windows of the entire experimental possible energy ranges, or in low energy ranges; while, for background windows in relatively higher energy ranges, this maximal acceptable fraction of residue background events can not be larger than ~10%. For a WIMP mass of 100 GeV with 20% background events in the windows of the entire experimental possible energy ranges, the reconstructed WIMP mass and the 1-sigma statistical uncertainty are ~97 GeV^{+61%}_{-35%} (~94 GeV^{+55%}_{-33%} for background-free data sets). Comment: 27 pages, 22 eps figures; v2: revised version for publication, references added and updated03/2010; -
Article: Extracting Dark Matter Properties Model-Independently from Direct Detection Experiments
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ABSTRACT: In this article I review model-independent procedures for extracting properties of Weakly Interacting Massive Particles (WIMPs) from direct Dark Matter detection experiments. Neither prior knowledge about the velocity distribution function of halo Dark Matter particles nor about their mass or cross sections on target nucleus is needed. The unique required information is measured recoil energies from experiments with different detector materials. Comment: 10 pages, to appear in the proceedings of the International Workshop on Dark Matter, Dark Eaergy, and Matter-Antimatter Asymmetry, Hsinchu, Taiwan, November 20-21, 200903/2010; -
Article: Uploading User-Defined Functions onto the AMIDAS Website
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ABSTRACT: The AMIDAS website has been established as an online interactive tool for running simulations and analyzing data in direct Dark Matter detection experiments. At the first phase of the website building, only some commonly used WIMP velocity distribution functions and elastic nuclear form factors have been involved in the AMIDAS code. In order to let the options for velocity distribution as well as for nuclear form factors be more flexible, we have extended the AMIDAS code to be able to include user-uploaded files with their own functions. In this article, I describe the preparation of files of user-defined functions onto the AMIDAS website. Some examples will also be given. Comment: 10 pages, part of the "Users' Guide to the AMIDAS Code and Website"10/2009; -
Article: The AMIDAS Website: An Online Tool for Direct Dark Matter Detection Experiments
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ABSTRACT: Following our long-term work on development of model-independent data analysis methods for reconstructing the one-dimensional velocity distribution function of halo WIMPs as well as for determining their mass and couplings on nucleons by using data from direct Dark Matter detection experiments directly, we combined the simulation programs to a compact system: AMIDAS (A Model-Independent Data Analysis System). For users' convenience an online system has also been established at the same time. AMIDAS has the ability to do full Monte Carlo simulations, faster theoretical estimations, as well as to analyze (real) data sets recorded in direct detection experiments without modifying the source code. In this article, I give an overview of functions of the AMIDAS code based on the use of its website. Comment: 4 pages, to appear in the proceedings of the 17th International Conference on Supersymmetry and the Unification of Fundamental Interactions (SUSY09), Boston, USA, 5-10 June, 200909/2009; -
Article: Determining the Mass of Dark Matter Particles with Direct Detection Experiments
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ABSTRACT: In this article I review two data analysis methods for determining the mass (and eventually the spin-independent cross section on nucleons) of Weakly Interacting Massive Particles with positive signals from direct Dark Matter detection experiments: a maximum likelihood analysis with only one experiment and a model-independent method requiring at least two experiments. Uncertainties and caveats of these methods will also be discussed. Comment: 24 pages, 10 figures, 1 reference added, typos fixed, published version, to appear in the NJP Focus Issue on "Dark Matter and Particle Physics"03/2009; -
Article: How Precisely Could We Identify WIMPs Model-Independently with Direct Dark Matter Detection Experiments
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ABSTRACT: In this talk we present data analysis methods for reconstructing the mass and couplings of Weakly Interacting Massive Particles (WIMPs) by using directly future experimental data (i.e., measured recoil energies) from direct Dark Matter detection. These methods are independent of the model of Galactic halo as well as of WIMPs. The basic ideas of these methods and the feasibility and uncertainties of applying them to direct detection experiments with the next generation detectors will be discussed. Comment: 14 pages, 8 figures, typos fixed, one conclusion modified, to appear in the proceedings of the Seventh International Heidelberg Conference on Dark Matter in Astro and Particle Physics (Dark 2009), Christchurch, New Zealand, 19-23 January, 200903/2009; -
Article: Improvement of the Determination of the WIMP Mass from Direct Dark Matter Detection Data
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ABSTRACT: Weakly Interacting Massive Particles (WIMPs) are one of the leading candidates for Dark Matter. We developed a model-independent method for determining the WIMP mass by using data (i.e., measured recoil energies) of direct detection experiments. Our method is independent of the as yet unknown WIMP density near the Earth, of the form of the WIMP velocity distribution, as well as of the WIMP-nucleus cross section. It requires however positive signals from at least two detectors with different target nuclei. At the first phase of this work we found a systematic deviation of the reconstructed WIMP mass from the real one for heavy WIMPs. Now we improved this method so that this deviation can be strongly reduced for even very high WIMP mass. The statistical error of the reconstructed mass has also been reduced. In a background-free evironment, a WIMP mass of ~ 50 GeV could in principle be determined with an error of ~ 35% with only 2 times 50 events.10/2008; -
Article: Constraining the Spin-Independent WIMP-Nucleon Coupling from Direct Dark Matter Detection Data
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ABSTRACT: Weakly Interacting Massive Particles (WIMPs) are one of the leading candidates for Dark Matter. For understanding the properties of WIMPs and identifying them among new particles produced at colliders (hopefully in the near future), determinations of their mass and their couplings on nucleons from direct Dark Matter detection experiments are essential. Based on our method for determining the WIMP mass model-independently from experimental data, we present a way to also estimate the spin-independent (SI) WIMP-nucleon coupling by using measured recoil energies directly. This method isindependent of the as yet unknown velocity distribution of halo WIMPs. In spite of the uncertainty of the local WIMP density (of a factor of ~ 2), at least an upper limit on the SI WIMP-nucleon coupling could be given, once two (or more) experiments with different target nuclei obtain positive signals. In a background-free environment, for a WIMP mass of 100 GeV its SI coupling on nucleons could in principle be estimated with a statistical error of only ~ 15% with just 50 events from each experiment. Comment: 5 pages, 4 figures, plots updated, to appear in the proceedings of Identification of Dark Matter (IDM 2008), Stockholm, Sweden, 18-22 August, 200809/2008; -
Article: Model-Independent Determination of the WIMP Mass from Direct Dark Matter Detection Data
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ABSTRACT: Weakly Interacting Massive Particles (WIMPs) are one of the leading candidates for Dark Matter. We develop a model-independent method for determining the mass $m_\chi$ of the WIMP by using data (i.e., measured recoil energies) of direct detection experiments. Our method is independent of the as yet unknown WIMP density near the Earth, of the form of the WIMP velocity distribution, as well as of the WIMP-nucleus cross section. However, it requires positive signals from at least two detectors with different target nuclei. In a background-free environment, $m_\chi \sim 50$ GeV could in principle be determined with an error of $\sim 35%$ with only $2 \times 50$ events; in practice upper and lower limits on the recoil energy of signal events, imposed to reduce backgrounds, can increase the error. The method also loses precision if $m_\chi$ significantly exceeds the mass of the heaviest target nucleus used.05/2008;
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2007
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Rheinische Friedrich-Wilhelms-Universität Bonn
- Physics Institute
Bonn, North Rhine-Westphalia, Germany
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