3,106 research outputs found

    Search for dark matter at the LHC using missing transverse energy

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    Results are presented for a search for dark matter at the LHC using the signatures of a monojet plus missing transverse energy and a monophoton plus missing transverse energy. The data were collected by the CMS detector at the LHC with pp collisions at a centre-of-mass energy of 7 TeV and an integrated luminosity of 5 inverse femtobarns. In the absence of an excess of events in the data compared to the Standard Model prediction, limits are set on the dark matter-nucleon scattering cross section which can be directly compared with bounds from the direct detection experiments.Comment: Contribution to Moriond Cosmology 2012 proceeding

    Search for New Physics with Monojet plus missing transverse energy at CMS

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    Results are presented for the search for new physics in the monojet plus missing transverse energy channel using pp collision data at a centre-of-mass energy of 7 TeV. The data were collected by the CMS detector at the LHC, and correspond to an integrated luminosity of 36 pb-1. The number of observed events is found to be in good agreement with Standard Model predictions and limits are placed on parameters in the framework of the ADD model and unparticles.Comment: Proceedings for the DPF2011 conference (Brown University, Providence, RI, USA

    Ratios of WW and ZZ cross sections at large boson pTp_T as a constraint on PDFs and background to new physics

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    We motivate a measurement of various ratios of WW and ZZ cross sections at the Large Hadron Collider (LHC) at large values of the boson transverse momentum (pTMW,Zp_T\gtrsim M_{W,Z}). We study the dependence of predictions for these cross-section ratios on the multiplicity of associated jets, the boson pTp_T and the LHC centre-of-mass energy. We present the flavour decomposition of the initial-state partons and an evaluation of the theoretical uncertainties. We show that the W+/WW^+/W^- ratio is sensitive to the up-quark to down-quark ratio of parton distribution functions (PDFs), while other theoretical uncertainties are negligible, meaning that a precise measurement of the W+/WW^+/W^- ratio at large boson pTp_T values could constrain the PDFs at larger momentum fractions xx than the usual inclusive WW charge asymmetry. The W±/ZW^\pm/Z ratio is insensitive to PDFs and most other theoretical uncertainties, other than possibly electroweak corrections, and a precise measurement will therefore be useful in validating theoretical predictions needed in data-driven methods, such as using W(ν)W(\to\ell\nu)+jets events to estimate the Z(ννˉ)Z(\to\nu\bar{\nu})+jets background in searches for new physics at the LHC. The differential WW and ZZ cross sections themselves, dσ/dpT{\rm d}\sigma/{\rm d}p_T, have the potential to constrain the gluon distribution, provided that theoretical uncertainties from higher-order QCD and electroweak corrections are brought under control, such as by inclusion of anticipated next-to-next-to-leading order QCD corrections.Comment: 33 pages, 13 figures. v2: expanded version published in JHE

    Constraining Dark Matter Interactions with Pseudoscalar and Scalar Mediators Using Collider Searches for Multi-jets plus Missing Transverse Energy

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    The mono-jet search, looking for events involving missing transverse energy (MET) plus one or two jets, is the most prominent collider dark matter search. We show that multi-jet searches, which look for MET plus two or more jets, are significantly more sensitive than the mono-jet search for pseudoscalar- and scalar-mediated interactions. We demonstrate this in the context of a simplified model with a pseudoscalar interaction that explains the excess in GeV energy gamma rays observed by the Fermi Large Area Telescope. We show that multi-jet searches already constrain a pseudoscalar interpretation of the excess in much of the parameter space where the mass of the mediator (mA) is more than twice the dark matter mass (mDM). With the forthcoming run of the LHC at higher energies, the remaining regions of the parameter space where mA>2mDM will be fully explored. Furthermore, we highlight the importance of complementing the mono-jet final state with multi-jet final states to maximise the sensitivity of the search for the production of dark matter at colliders.Comment: 7 pages, 2 figures. v2: Updated to match the journal versio

    Uterine contractions in rodent models and humans

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    Aberrant uterine contractions can lead to preterm birth and other labour complications and are a significant cause of maternal morbidity and mortality. To investigate the mechanisms underlying dysfunctional uterine contractions, researchers have used experimentally tractable small animal models. However, biological differences between humans and rodents change how researchers select their animal model and interpret their results. Here, we provide a general review of studies of uterine excitation and contractions in mice, rats, guinea pigs, and humans, in an effort to introduce new researchers to the field and help in the design and interpretation of experiments in rodent models

    Quantum walk approach to simulating parton showers

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    This paper presents a novel quantum walk approach to simulating parton showers on a quantum computer. We demonstrate that the quantum walk paradigm offers a natural and more efficient approach to simulating parton showers on quantum devices, with the emission probabilities implemented as the coin flip for the walker, and the particle emissions to either gluons or quark pairs corresponding to the movement of the walker in two dimensions. A quantum algorithm is proposed for a simplified, toy model of a 31-step, collinear parton shower, hence significantly increasing the number of steps of the parton shower that can be simulated compared to previous quantum algorithms. Furthermore, it scales efficiently: the number of possible shower steps increases exponentially with the number of qubits, and the circuit depth grows linearly with the number of steps. Reframing the parton shower in the context of a quantum walk therefore brings dramatic improvements, and is a step towards extending the current quantum algorithms to simulate more realistic parton showers

    A multi-tier trust-based security mechanism for vehicular ad-hoc network communications

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    Securing communications in vehicle ad hoc networks is crucial for operations. Messages exchanged in vehicle ad hoc network communications hold critical information such as road safety information, or road accident information and it is essential these packets reach their intended destination without any modification. A significant concern for vehicle ad hoc network communications is that malicious vehicles can intercept or modify messages before reaching their intended destination. This can hamper vehicle ad hoc network operations and create safety concerns. The multi-tier trust management system proposed in this paper addresses the concern of malicious vehicles in the vehicle ad hoc network using three security tiers. The first tier of the proposed system assigns vehicles in the vehicle ad hoc network a trust value based on behaviour such as processing delay, packet loss and prior vehicle behavioural history. This will be done by selecting vehicles as watchdogs to observe the behaviour of neighbouring vehicles and evaluate the trust value. The second tier is to protect the watchdogs, which is done by watchdogs’ behaviour history. The third security tier is to protect the integrity of data used for trust value calculation. Results show that the proposed system is successful in identifying malicious vehicles in the VANET. It also improves the packet delivery ratio and end-to-end delay of the vehicle ad hoc network in the presence of malicious vehicles

    HERMITE NUMERICAL METHOD TO ESTIMATE THE RADON AND RADIUM EFFECTS OF THE SOIL IN BARTELLA REGION

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    The Hermite numerical interpolation method used to estimate and predict the radon and radium concentrations, from some of the experimental measurements made on the soil samples of the Bartella region in Iraq. The results obtained from deductible mathematical method were close to real experimental results. Predicted results are in the range of 80.04–4051.59 Bq/m3radon concentrations and 0.322–17.276 Bq/Kgradium concentrations corresponding to 200-10000 tracks of alpha particles. The maximum errors were less than 0.289 and 1.172 percent for radon and radium concentrations, respectively. The effects of radium and radon radiations estimated of soil in the studied area depend on its concentrations, a higher number of alpha particle tracks mean high radiation concentration, the high radiation will cause human health damage. The values are below 370 Bq/Kg the recommended radium concentration permissible values, by the Organization ащк Economic Cooperation and Development (OECD), the studied area is safe from hazards on health of radium and radon exposure from the soi

    Retinal Vasculitis: A Case Study

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    Purpose: To describe a case of idiopathic retinal vasculitis. Methods: Case report and literature review. Case: A healthy 25-year-old female presented with a one-week history of a large floater in her right eye. Patient’s subjective complaint of floaters, including the scotoma on VF and the FA findings were most consistent with retinal vasculitis displaying predominant venous involvement. However, findings for acute macular neuroretinopathy and multiple evanescent white dot syndrome (MEWDS) were present as well. Autoimmune and infectious disease panels were negative. Neuro consult and brain MRI showed nonspecific, non contributory findings. Several weeks later, following Medrol dose pack, patient reported significantly improved visual field and this was consistent with improved clinical and diagnostic findings. Conclusion: Although cases of retinal vasculitis have been linked to infectious, neoplastic, systemic and autoimmune diseases, idiopathic cases can present concurrently with other retinopathies

    Impact of Evaporation on the Performance of Ant Colony Optimization-Based Routing Protocols on the Wireless Sensor Network

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    Wireless Sensor Network (WSN) has the characteristics limited computing, memory and energy, so a routing protocol that supports WSN network performance is needed. Routing protocols based Ant Colony Optimization (ACO) are very suitable for use in WSN for routing data packets. In this report, we will try out several kinds of parameter values that bear on the pheromone evaporation (ρ) on the ACO algorithms applied to the WSN routing protocol with grid topology on the number of nodes variables in the WSN network. Where this can increase the number of delivery packets on a busy WSN network and each node transmits a packet continuously. From the results, the value of ρ 0.75 makes WSN performance on the grid topology with the number of nodes 12 and 30 very good in terms of the delivery packet, but with the number of nodes 70 the value of ρ 0.70 makes WSN performance better than the delivery packet side
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