Using Subsystem MT2 for Complete Mass Determinations in Decay Chains with Missing Energy at Hadron Colliders

We propose to use the MT2 concept to measure the masses of all particles in SUSY-like events with two unobservable, identical particles. To this end we generalize the usual notion of MT2 and define a new MT2(n,p,c) variable, which can be applied to various subsystem topologies, as well as the full event topology. We derive analytic formulas for its endpoint MT2{max}(n,p,c) as a function of the unknown test mass Mc of the final particle in the subchain and the transverse momentum pT due to radiation from the initial state. We show that the endpoint functions MT2{max}(n,p,c)(Mc,pT) may exhibit three different types of kinks and discuss the origin of each type. We prove that the subsystem MT2(n,p,c) variables by themselves already yield a sufficient number of measurements for a complete determination of the mass spectrum (including the overall mass scale). As an illustration, we consider the simple case of a decay chain with up to three heavy particles, X2 -> X1 -> X0, which is rather problematic for all other mass measurement methods. We propose three different MT2-based methods, each of which allows a complete determination of the masses of particles X0, X1 and X2. The first method only uses MT2(n,p,c) endpoint measurements at a single fixed value of the test mass Mc. In the second method the unknown mass spectrum is fitted to one or more endpoint functions MT2{max}(n,p,c)(Mc,pT) exhibiting a kink. The third method is hybrid, combining MT2 endpoints with measurements of kinematic edges in invariant mass distributions. As a practical application of our methods, we show that the dilepton W+W- and tt-bar samples at the Tevatron can be used for an independent determination of the masses of the top quark, the W boson and the neutrino, without any prior assumptions.Comment: 47 pages, 9 figures. revised version, published in JHEP. Major addition: a new appendix with the complete set of formulas for the MT2 endpoints as functions of the upstream transverse momentum pT and test mass M

Planar Induced Subgraphs of Sparse Graphs

We show that every graph has an induced pseudoforest of at least $n-m/4.5$ vertices, an induced partial 2-tree of at least $n-m/5$ vertices, and an induced planar subgraph of at least $n-m/5.2174$ vertices. These results are constructive, implying linear-time algorithms to find the respective induced subgraphs. We also show that the size of the largest $K_h$-minor-free graph in a given graph can sometimes be at most $n-m/6+o(m)$.Comment: Accepted by Graph Drawing 2014. To appear in Journal of Graph Algorithms and Application

Evaluation of long-term tropospheric NO2 columns and the effect of different ecosystem in Yangtze River Delta

AbstractThe spatial and temporal characters of tropospheric NO2 column over Yangtze River Delta (YZD) are analyzed using monthly averaged tropospheric NO2 column densities from GOME (1996-2002) and SCIAMACHY (2003-2010) measurements. In addition, with the NO2 column densities data and the land cover maps of YZD, the characters of NO2 concentration over different ecosystem have been analyzed. The results indicated that the tropospheric NO2 column densities in YZD increased distinctly from 1996 to 2010 and it showed distinct regional and seasonal variation characteristics. It has the highest concentration in winter while lowest in summer. It also presents zonal distribution and decreasing along the Yangtze River from eastern to western. Under the influence of the urbanization process, the highest NO2 column densities appeared at cities and metropolis which are located in the Shanghai, Nanjing as well as Hangzhou. Moreover the lowest column densities appeared at the forest areas which are in the south and west of Zhejiang province. The sharp increasing of appeared in water bodies, followed urban area and water bodies. The lowest increasing of NO2 column appeared in grassland. Furthermore, we inferred the ground-level NO2 concentration from the GOME and SCIAMACHY data in this paper. We compared with the dry plus of N deposition which inferred from the remote sensing data and the mass concentration of N dry deposition from the control experiments, they performed significant correlation (P<0.001), and have the high R value (R2=0.86)

Assess the effect of different degrees of urbanization on land surface temperature using remote sensing images

AbstractUrbanization is a human-dominated process and has greatly impacted biodiversity, ecosystem processes, and regional climate. In this study we assess the effect of different degrees of urbanization on land surface temperature using remote sensing images. Landsat TM images were used for land surface temperature retrieval using the algorithm proposed by Artis and Carnahan. ALOS multispectral images were used for landcover classification using classification trees in three study areas, namely Xicheng district(A), Haidian district(B), Shijingshan district(C), of different degrees of urbanization in Beijing. Landcover-specific surface temperatures were estimated through an inversion alorithm. At the different degrees of urbanization, reducing the within-pixel coverage ratio of vegetations will result in an land surface temperature rise. Quantitative assessment of the relationship between different degrees of urbanization and land surface temperature was simulated by an urbanization index which integrates the coverage ratio of built-up landcover type and the cell-average NDVI. Urbanization indices of the Xicheng district, Haidian district, Shijingshan district were calculated to be 0.91, 0.72, and, 0.55 respectively. Such results are consistent with the trend of evaluation using quantitative estimation land surface temperature

New method for characterizing electron mediators in microbial systems using a thin-layer twin-working electrode cell

Microbial biofilms are significant ecosystems where the existence of redox gradients drive electron transfer often via soluble electron mediators. This study describes the use of two interfacing working electrodes (WEs) to simulate redox gradients within close proximity (250 µm) for the detection and quantification of electron mediators. By using a common counter and reference electrode, the potentials of the two WEs were independently controlled to maintain a suitable “voltage window”, which enabled simultaneous oxidation and reduction of electron mediators as evidenced by the concurrent anodic and cathodic currents, respectively. To validate the method, the electrochemical properties of different mediators (hexacyanoferrate, HCF, riboflavin, RF) were characterized by stepwise shifting the “voltage window” (ranging between 25 and 200 mV) within a range of potentials after steady equilibrium current of both WEs was established. The resulting differences in electrical currents between the two WEs were recorded across a defined potential spectrum (between −1 V and +0.5 V vs. Ag/AgCl). Results indicated that the technique enabled identification (by the distinct peak locations at the potential scale) and quantification (by the peak of current) of the mediators for individual species as well as in an aqueous mixture. It enabled a precise determination of mid-potentials of the externally added mediators (HCF, RF) and mediators produced by pyocyanin-producing Pseudomonas aeruginosa (WACC 91) culture. The twin working electrode described is particularly suitable for studying mediator-dependent microbial electron transfer processes or simulating redox gradients as they exist in microbial biofilms

How can the Odderon be detected at RHIC and LHC

The Odderon remains an elusive object, 33 years after its invention. The Odderon is now a fundamental object in QCD and CGC and it has to be found experimentally if QCD and CGC are right. In the present paper, we show how to find it at RHIC and LHC. The most spectacular signature of the Odderon is the predicted difference between the differential cross-sections for proton-proton and antiproton-proton at high s and moderate t. The experiment can be done by using the STAR detector at RHIC and by combining these future data with the already present UA4/2 data. The Odderon could also be found by ATLAS exeperiment at LHC by performing a high-precision measurement of the real part of the hadron elastic scattering amplitude at small t.Comment: 14 pages, 16 figures, two typographical errors corrected and acknowledgments adde

Occupational exposure assessment for power frequencyelectromagnetic fields

Exposure assessment is the determination or estimate of the magnitude, frequency of occurrence, and rate of exposure of an individual or a group to an environmental agent. The agents of interest in this case are the electric and magnetic fields (EMF) in the extreme low frequency range that includes the power frequency of 50/60 Hz. There are an increasing concern that exposure to EMF may be associated with biological and health effects. This concern has prompted numerous measurement projects and the development of instrumentation, methodologies, and exposure models and simulations. This paper identifies the status of EMF exposure assessment research related to occupational exposures. It draws the results to emphasize the unique aspects of EMF exposures in the home and utilities environments, and highlights the research needs. The intensities of electromagnetic fields have been measured under power transmission and distribution lines, at substations and industrial plants and near various electric devices including domestic electrical equipment. The field intensities have been related to the exposure time (duration of staying) in the different areas and have been compared with the international established standards. The data presented are useful for understanding the levels of electromagnetic fields that can be encountered in various places and also for estimating possible occupational and residential exposure level

Occupational exposure assessment for power frequencyelectromagnetic fields

Exposure assessment is the determination or estimate of the magnitude, frequency of occurrence, and rate of exposure of an individual or a group to an environmental agent. The agents of interest in this case are the electric and magnetic fields (EMF) in the extreme low frequency range that includes the power frequency of 50/60 Hz. There are an increasing concern that exposure to EMF may be associated with biological and health effects. This concern has prompted numerous measurement projects and the development of instrumentation, methodologies, and exposure models and simulations. This paper identifies the status of EMF exposure assessment research related to occupational exposures. It draws the results to emphasize the unique aspects of EMF exposures in the home and utilities environments, and highlights the research needs. The intensities of electromagnetic fields have been measured under power transmission and distribution lines, at substations and industrial plants and near various electric devices including domestic electrical equipment. The field intensities have been related to the exposure time (duration of staying) in the different areas and have been compared with the international established standards. The data presented are useful for understanding the levels of electromagnetic fields that can be encountered in various places and also for estimating possible occupational and residential exposure level

Neutralino Decays at the CERN LHC

We study the distribution of lepton pairs from the second lightest neutralino decay \tchi^0_2\to\tchi^0_1 l^+l^-. This decay mode is important to measure the mass difference between \tchi^0_2 and the lightest neutralino \tchi^0_1, which helps to determine the parameters of the minimal supersymmetric standard model at the CERN LHC. We found that the decay distribution strongly depends on the values of underlying MSSM parameters. For some extreme cases, the amplitude near the end point of the lepton invariant mass distribution can be suppressed so strongly that one needs the information of the whole m_{ll} distribution to extract m_{\tchi^0_2}-m_{\tchi^0_1}. On the other hand, if systematic errors on the acceptance can be controlled, this distribution can be used to constrain slepton masses and the Z\tchi^0_2\tchi^0_1 coupling. Measurements of the velocity distribution of \tchi^0_2 from samples near the end point of the m_{ll} distribution, and of the asymmetry of the p_T of leptons, would be useful to reduce the systematic errors.Comment: 23 pages, latex2e, 9 figures, minor change, accepted to PR

Near-Earth asteroid sample return missions

The rate of discovery of new NEAs and the success of D-S 1 and NEAR-Shoemaker, suggest that sample return from NEAs is now technically feasible. Here we present a summary of a recent workshop on the topic