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‣ A search for anisotropy in the arrival directions of ultra high energy cosmic rays recorded at the Pierre Auger Observatory

Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, Ivone Freire da Mota e; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muniz, J.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Antici'
Fonte: IOP PUBLISHING LTD; BRISTOL Publicador: IOP PUBLISHING LTD; BRISTOL
Tipo: Artigo de Revista Científica
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Observations of cosmic rays arrival directions made with the Pierre Auger Observatory have previously provided evidence of anisotropy at the 99% CL using the correlation of ultra high energy cosmic rays (UHECRs) with objects drawn from the Veron-Cetty Veron catalog. In this paper we report on the use of three catalog independent methods to search for anisotropy. The 2pt-L, 2pt+ and 3pt methods, each giving a different measure of self-clustering in arrival directions, were tested on mock cosmic ray data sets to study the impacts of sample size and magnetic smearing on their results, accounting for both angular and energy resolutions. If the sources of UHECRs follow the same large scale structure as ordinary galaxies in the local Universe and if UHECRs are deflected no more than a few degrees, a study of mock maps suggests that these three method can efficiently respond to the resulting anisotropy with a P-value = 1.0% or smaller with data sets as few as 100 events. using data taken from January 1, 2004 to July 31, 2010 we examined the 20, 30, ... , 110 highest energy events with a corresponding minimum energy threshold of about 49.3 EeV. The minimum P-values found were 13.5% using the 2pt-L method, 1.0% using the 2pt+ method and 1.1% using the 3pt method for the highest 100 energy events. In view of the multiple (correlated) scans performed on the data set...

‣ Growth, metabolic status and ovarian function in buffalo (Bubalus bubalis) heifers fed a low energy or high energy diet

CAMPANILE, G; BARUSELLI, Pietro Sampaio; VECCHIO, Domenico; PRANDI, Alfonso; NEGLIA, Gianluca; CARVALHO, N. A. T; SALES, J. N. S; GASPARRINI, Bianca; D'OCCHIO, M. J
Fonte: Amsterdam Publicador: Amsterdam
Tipo: Artigo de Revista Científica
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The aim was to establish the capacity of buffalo heifers to adapt their metabolic requirements to a low energy diet. Murrah buffalo (Bubalus bubalis) heifers undergoing regular estrous cycles were randomly assigned by age, live weight (LW) and body condition score (BCS) to a high energy group (HE, 5.8 milk forage units (MFU)/day, n = 6) or low energy group (LE, 3.6 MFU/day, n = 6). Circulating concentrations of metabolic substrates, metabolic hormones and reproductive hormones were determined weekly for 19 weeks. Ovarian follicular characteristics and oocyte parameters were also ascertained weekly. Heifers fed the LE diet had a better dry matter conversion than heifers fed the HE diet and the calculated daily energy provision was negative for heifers fed the LE diet (−0.248 MFU) and positive for heifers fed the HE diet (5.4 MFU). Heifers fed the HE diet had an increase in 50 kg LW over the duration of the study whereas LW remained constant for heifers fed the LE diet. The BCS of heifers fed the HE diet (4.2) was greater (P < 0.05) than the BCS for heifers fed the LE diet (3.4). Heifers fed the HE diet had greater (P < 0.05) circulating concentrations of metabolic substrates (glucose, total cholesterol and HDL cholesterol) and metabolic hormones (insulin...

‣ Estudo de tecnologias aplicáveis à automação da medição de energia elétrica residencial visando à minimização de perdas.; Study of applicable technologies for residential electric energy metering automation in order to minimize losses.

Paulino, Clóvis Aparecido
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/10/2006 Português
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Atualmente a medição de energia elétrica para residências em centros urbanos é realizada por meio de medidores eletromecânicos lidos de forma manual. Neste processo uma série de problemas foram observados, dos quais se destacam: erros de leitura, dificuldade de acesso ao ponto de medição, bancos de dados sem atualização, dentre outros. A automação do processo de medição e da leitura, com base nos medidores existentes ou com o uso de medidores eletrônicos da energia elétrica, além de resolver os problemas citados, tem potencialmente uma série de vantagens, que incluem: combate a fraudes e furto de energia, implementação de tarifas diferenciadas em função da hora de consumo (tarifa amarela), corte e religamento remoto de energia, implementação de programas de energia pré-paga, levantamento de curvas de carga e eliminação de erros e custos do processo de leitura manual. Por outro lado observa-se que existem no Brasil cerca de 43 milhões de medidores residenciais instalados, sendo relativamente baixos os custos dos medidores eletromecânicos e do sistema de leitura manual. Desta forma, somente será possível implementar sistemas de automação da medição de energia elétrica residencial se os sistemas ora propostos forem ao mesmo tempo de custo reduzido e altamente confiáveis. O sistema de automação em estudo irá considerar inclusive o aproveitamento dos medidores eletromecânicos existentes...

‣ Breve análise da estratégia da União Europeia (UE) para a eficiência energética do ambiente construído; Brief analysis of the European Union (EU) strategy for the energy efficiency of the built environment

Torgal, Fernando Pacheco
Fonte: Associação Nacional de Tecnologia do Ambiente Construído (ANTAC) Publicador: Associação Nacional de Tecnologia do Ambiente Construído (ANTAC)
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
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O aquecimento global é um dos mais graves problemas com que se depara o Planeta Terra. Este problema se origina do aumento da concentração de gases de efeito estufa (CO2) na atmosfera. Esses gases provêm, na sua maioria, da queima de combustíveis fósseis para produção de energia. Na Europa as emissões relacionadas com a produção de energia representam a maior parte das emissões totais. Portanto, a fim de lidar com o problema do aquecimento global, os países da União Européia (UE) decidiram que em 2020 seu nível de emissões conjunto será 20% inferior ao de 1990 e ainda que em 2050 essa redução deverá situar-se entre 80% e 95% abaixo do nível de emissões de 1990. Além disso, a UE se comprometeu a aumentar em 20% o consumo de energia oriunda de fontes renováveis. O aumento da eficiência energética em edifícios novos e existentes é fundamental para a transformação do sistema energético da UE. O presente artigo analisa sucintamente a estratégia da UE para a eficiência energética no ambiente construído.; Climate change is one of the most serious environmental problems that the planet faces today. This problem is due to an increasing concentration of of greenhouse gases (CO2) in the atmosphere. Most of those gases originate from the burning of fossil fuels for energy production. Energy related emissions account for the largest share of the EU's total greenhouse gas emissions. Therefore...

‣ Barriers to and driving forces for energy efficiency in the portuguese industrial SMEs

Pereira, Vasco Manuel Figueiredo
Fonte: Universidade da Beira Interior Publicador: Universidade da Beira Interior
Tipo: Dissertação de Mestrado
Publicado em //2011 Português
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Industry accounts for about one-third of global final energy use. However, despite the need for increased industrial energy efficiency, studies indicate that cost-effective energy efficiency measures are not always implemented, resulting in an ―energy efficiency gap‖, which is explained by the existence of barriers to energy efficiency. Considering that SMEs are usually less efficient than Large Enterprises (LEs), this study based on a survey among Portuguese industrial SMEs, investigates the barriers that are inhibiting the adoption of energy efficiency measures and how they vary over firm‘s characteristics and over sector. Additionally the study points some drivers that could overcome those barriers. The results support the existence of barriers to energy efficiency in Portuguese industry, where lack of capital and other investments priorities were considered the most important ones. Furthermore it concludes that factors related with public policy could overcome those barriers, suggesting the need of public intervention to increase the levels of energy efficiency in the Portuguese industry.

‣ The economy-wide impact of controlling energy consumption in Indonesia: An analysis using a Social Accounting Matrix framework

Hartono, Djoni; Resosudarmo, Budy
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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Escalating oil prices and the need to control carbon emissions sound the alarm for Indonesia to reduce or be more efficient in its energy use. Instead of eliminating the fuel oil subsidy to promote better and more efficient use of energy, the Indonesian g

‣ Systematics of High Temperature Perturbation Theory: The Two-Loop Electron Self-Energy in QED

Mottola, Emil; Szep, Zsolt
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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In order to investigate the systematics of the loop expansion in high temperature gauge theories beyond the leading order hard thermal loop (HTL) approximation, we calculate the two-loop electron proper self-energy in high temperature QED. The two-loop bubble diagram contains a linear infrared divergence. Even if regulated with a non-zero photon mass M of order of the Debye mass, this infrared sensitivity implies that the two-loop self-energy contributes terms to the fermion dispersion relation that are comparable to or even larger than the next-to-leading-order (NLO) contributions at one-loop. Additional evidence for the necessity of a systematic restructuring of the loop expansion comes from the explicit gauge parameter dependence of the fermion damping rate at both one and two-loops. The leading terms in the high temperature expansion of the two-loop self-energy for all topologies arise from an explicit hard-soft factorization pattern, in which one of the loop integrals is hard, nested inside a second loop integral which is soft. There are no hard-hard contributions to the two-loop Sigma at leading order at high T. Provided the same factorization pattern holds for arbitrary ell loops, the NLO high temperature contributions to the electron self-energy come from ell-1 hard loops factorized with one soft loop integral. This hard-soft pattern is both a necessary condition for the resummation over ell to coincide with the one-loop self-energy calculated with HTL dressed propagators and vertices...

‣ Constraining the runaway dilaton and quintessential dark energy

Neupane, Ishwaree P.; Trowland, Holly
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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Dark Energy is some of the weirdest and most mysterious stuff in the universe that tends to increase the rate of expansion of the universe. Two commonly known forms of dark energy are the cosmological constant, a constant energy density filling space homogeneously, and scalar fields such as quintessence or moduli whose energy density can vary with time. We explore one particular model for dynamic dark energy; quintessence driven by a scalar dilaton field. We propose an ansatz for the form of the dilaton field, $|\phi(a)|/m_P \equiv \alpha_1 \ln t+ \alpha_2 t^n=\alpha\ln a+ \beta\, a^{2\zeta}$, where $a$ is the scale factor and $\alpha$ and $\zeta$ are parameters of the model. This phenomenological ansatz for $\phi$ can be motivated by generic solutions of a scalar dilaton field in many effective string theory and string-inspired gravity models in four dimensions. Using a compilation of current data including type Ia supernovae, we impose observational constraints on the slope parameters like $\alpha$ and $\zeta$ and then discuss the relation of our results to analytical constrains on various cosmological parameters, including the dark energy equation of state. Sensible constraints are imposed on model parameters like $\alpha$ and $\zeta$ as well as on the dark energy/dark matter couplings using results from structure formation. The constraints of this model are shown to encompass the cosmological constant limit within $1\sigma$ error bars.; Comment: 32 pages...

‣ Dark energy cosmology: the equivalent description via different theoretical models and cosmography tests

Bamba, Kazuharu; Capozziello, Salvatore; Nojiri, Shin'ichi; Odintsov, Sergei D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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We review different dark energy cosmologies. In particular, we present the $\Lambda$CDM cosmology, Little Rip and Pseudo-Rip universes, the phantom and quintessence cosmologies with Type I, II, III and IV finite-time future singularities and non-singular dark energy universes. In the first part, we explain the $\Lambda$CDM model and well-established observational tests which constrain the current cosmic acceleration. After that, we investigate the dark fluid universe where a fluid has quite general equation of state (EoS) [including inhomogeneous or imperfect EoS]. All the above dark energy cosmologies for different fluids are explicitly realized, and their properties are also explored. It is shown that all the above dark energy universes may mimic the $\Lambda$CDM model currently, consistent with the recent observational data. Furthermore, special attention is paid to the equivalence of different dark energy models. We consider single and multiple scalar field theories, tachyon scalar theory and holographic dark energy as models for current acceleration with the features of quintessence/phantom cosmology, and demonstrate their equivalence to the corresponding fluid descriptions. In the second part, we study another equivalent class of dark energy models which includes $F(R)$ gravity as well as $F(R)$ Ho\v{r}ava-Lifshitz gravity and the teleparallel $f(T)$ gravity. The cosmology of such models representing the $\Lambda$CDM-like universe or the accelerating expansion with the quintessence/phantom nature is described. Finally...

‣ Notes on High Energy Limit of Bosonic Closed String Scattering Amplitudes

Chan, Chuan-Tsung; Lee, Jen-Chi; Yang, Yi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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We study bosonic closed string scattering amplitudes in the high-energy limit. We find that the methods of decoupling of high-energy zero-norm states and the high-energy Virasoro constraints, which were adopted in the previous works to calculate the ratios among high-energy open string scattering amplitudes of different string states, persist for the case of closed string. However, we clarify the previous saddle-point calculation for high-energy open string scattering amplitudes and claim that only (t,u) channel of the amplitudes is suitable for saddle-point calculation. We then discuss three evidences to show that saddle-point calculation for high-energy closed string scattering amplitudes is not reliable. By using the relation of tree-level closed and open string scattering amplitudes of Kawai, Lewellen and Tye (KLT), we calculate the high-energy closed string scattering amplitudes for arbitrary mass levels. For the case of high-energy closed string four-tachyon amplitude, our result differs from the previous one of Gross and Mende, which is NOT consistent with KLT formula, by an oscillating factor.; Comment: 14 pages, no figure. Equations and Conclusion added

‣ Upper limits of particle emission from high-energy collision and reaction near a maximally rotating Kerr black hole

Harada, Tomohiro; Nemoto, Hiroya; Miyamoto, Umpei
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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The center-of-mass energy of two particles colliding near the horizon of a maximally rotating black hole can be arbitrarily high if the angular momentum of either of the incident particles is fine-tuned, which we call a critical particle. We study particle emission from such high-energy collision and reaction in the equatorial plane fully analytically. We show that the unconditional upper limit of the energy of the emitted particle is given by 218.6% of that of the injected critical particle, irrespective of the details of the reaction and this upper limit can be realized for massless particle emission. The upper limit of the energy extraction efficiency for this emission as a collisional Penrose process is given by 146.6%, which can be realized in the collision of two massive particles with optimized mass ratio. Moreover, we analyze perfectly elastic collision, Compton scattering, and pair annihilation and show that net positive energy extraction is really possible for these three reactions. The Compton scattering is most efficient among them and the efficiency can reach 137.2%. On the other hand, our result is qualitatively consistent with the earlier claim that the mass and energy of the emitted particle are at most of order the total energy of the injected particles and hence we can observe neither super-heavy nor super-energetic particles.; Comment: 22 pages...

‣ Active Galactic Nuclei with Starbursts: Sources for Ultra High Energy Cosmic Rays

Biermann, P. L.; Becker, J. K.; Caramete, L.; Gergely, L. A.; Maris, I. C.; Meli, A.; de Souza, V.; Stanev, T.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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Ultra high energy cosmic ray events presently show a spectrum, which we interpret here as galactic cosmic rays due to a starburst in the radio galaxy Cen A pushed up in energy by the shock of a relativistic jet. The knee feature and the particles with energy immediately higher in galactic cosmic rays then turn into the bulk of ultra high energy cosmic rays. This entails that all ultra high energy cosmic rays are heavy nuclei. This picture is viable if the majority of the observed ultra high energy events come from the radio galaxy Cen A, and are scattered by intergalactic magnetic fields across most of the sky.; Comment: 4 pages, 1 figure, proceedings of "High-Energy Gamma-rays and Neutrinos from Extra-Galactic Sources", Heidelberg

‣ Baryon Binding Energy in Sakai-Sugimoto Model

Sadeghi, J.; Pahlavani, M. R.; Heshmatian, S.; Morad, R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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The binding energy of baryon has been studied in the dual $AdS_5\times S^5$ string theory with a black hole interior. In this picture baryon is constructed of a $D_5$ brane vertex wrapping on $S^5$ and $N_c$ fundamental strings connected to it. Here, we calculate the baryon binding energy in Sakai-Sugimoto model with a $D_4/D_8/\bar{D_8}$ in which the supersymmetry is completely broken. Also we check the $T$ dependence of the baryon binding energy. We believe that this model represents an accurate description of baryons due to the existence of Chern-Simones coupling with the gauge field on the brane. We obtain an analytical expression for the baryon binding energy . In that case we plot the baryon binding energy in terms of radial coordinate. Then by using the binding energy diagram, we determine the stability range for baryon configuration. And also the position and energy of the stable equilibrium point is obtained by the corresponding diagram. Also we plot the baryon binding energy in terms of temperature and estimate a critical temperature in which the baryon would be dissociated.; Comment: 14 pages, 1 fig

‣ Holographic dark energy in a universe with spatial curvature and massive neutrinos: a full Markov Chain Monte Carlo exploration

Li, Yun-He; Wang, Shuang; Li, Xiao-Dong; Zhang, Xin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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In this paper, we report the results of constraining the holographic dark energy model with spatial curvature and massive neutrinos, based on a Markov Chain Monte Carlo global fit technique. The cosmic observational data include the full WMAP 7-yr temperature and polarization data, the type Ia supernova data from Union2.1 sample, the baryon acoustic oscillation data from SDSS DR7 and WiggleZ Dark Energy Survey, and the latest measurements of $H_0$ from HST. To deal with the perturbations of dark energy, we adopt the parameterized post-Friedmann method. We find that, for the simplest holographic dark energy model without spatial curvature and massive neutrinos, the phenomenological parameter $c<1$ at more than $4\sigma$ confidence level. The inclusion of spatial curvature enlarges the error bars and leads to $c<1$ only in about $2.5\sigma$ range; in contrast, the inclusion of massive neutrinos does not have significant influence on $c$. We also find that, for the holographic dark energy model with spatial curvature but without massive neutrinos, the $3\sigma$ error bars of the current fractional curvature density $\Omega_{k0}$ are still in order of $10^{-2}$; for the model with massive neutrinos but without spatial curvature, the $2\sigma$ upper bound of the total mass of neutrinos is $\sum m_{\nu} < 0.48$ eV. Moreover...

‣ GZK cutoff distortion due to the energy error distribution shape

Albuquerque, Ivone F. M.; Smoot, George F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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The observed energy spectrum of ultra high energy cosmic rays (UHECR) is distorted by errors in the energy reconstruction. Here we show that if the shape of the error distribution is lognormal, the high end of the cosmic ray spectrum will be distorted. This is distinct and potentially more significant than the effect of the magnitude of the error in the energy. We estimate the UHECR spectrum at the Earth assuming it is originated from a cosmological flux. We then convolute this flux assuming a lognormal error in the energy. We show that if the standard deviation of the lognormal error distribution is equal or larger than 0.25, both the shape and the normalization of the measured energy spectra will be modified significantly. As a consequence the GZK cutoff might be sufficiently smeared and as not to be seen. This result is independent of the power law of the cosmological flux. As a conclusion we show that in order to establish the presence or not of the GZK feature, not only more data is needed but also that the shape of the energy error distribution has to be known well.; Comment: 4 pages, 6 figures; to appear in Astroparticle Physics

‣ Energy Loss of Charm Quarks in the Quark-Gluon Plasma: Collisional vs Radiative

Mustafa, Munshi G.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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Considering the collisional energy loss rates of heavy quarks from hard light parton interactions the total energy loss of a charm quark for a static medium has been computed. For the energy range $E\sim (5-10)$ GeV of charm quark, it is found to be almost same order as that of radiative ones estimated to a first order opacity expansion. The collisional energy loss will become much more important for lower energy charm quarks and this feature could be very interesting for phenomenology of hadrons spectra. Using such collisional energy loss rates we estimate the momentum loss distribution employing a Fokker-Planck equation and the total energy loss of a charm quark for an expanding quark-gluon plasma under conditions resembling the RHIC energies. The fractional collisional energy loss is found to be suppressed by a factor of 5 as compared to static case and does not depend linearly on the system size. We also investigate the heavy to light hadrons $D/\pi$ ratio at moderately large (5-10) GeV/$c$ transverse momenta and comment on its enhancement.; Comment: 14 pages, 6 figures; this version is compiled with various sections than the earlier one along with additional discussion, one extra figure (Fig. 3) and two new curves in Fig. 4 in support of one approximation; revised version accepted in Phys. Rev. C

‣ Energy-Dependent GRB Pulse Width due to the Curvature Effect and Intrinsic Band Spectrum

Peng, Z. Y.; Zhao, X. H.; Yin, Y.; Bao, Y. Y.; Ma, L.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 16/04/2012 Português
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Previous studies have found that the width of gamma-ray burst (GRB) pulse is energy dependent and that it decreases as a power-law function with increasing photon energy. In this work we have investigated the relation between the energy dependence of pulse and the so-called Band spectrum by using a sample including 51 well-separated fast rise and exponential decay long-duration GRB pulses observed by BATSE (Burst and Transient Source Experiment on the Compton Gamma Ray Observatory). We first decompose these pulses into rise, and decay phases and find the rise widths, and the decay widths also behavior as a power-law function with photon energy. Then we investigate statistically the relations between the three power-law indices of the rise, decay and total width of pulse (denoted as $\delta_r$, $\delta_d$ and $\delta_w$, respectively) and the three Band spectral parameters, high-energy index ($\alpha$), low-energy index ($\beta$) and peak energy ($E_p$). It is found that (1)$\alpha$ is strongly correlated with $\delta_w$ and $\delta_d$ but seems uncorrelated with $\delta_r$; (2)$\beta$ is weakly correlated with the three power-law indices and (3)$E_p$ does not show evident correlations with the three power-law indices. We further investigate the origin of $\delta_d-\alpha$ and $\delta_w-\alpha$. We show that the curvature effect and the intrinsic Band spectrum could naturally lead to the energy dependence of GRB pulse width and also the $\delta_d-\alpha$ and $\delta_w-\alpha$ correlations. Our results would hold so long as the shell emitting gamma rays has a curve surface and the intrinsic spectrum is a Band spectrum or broken power law. The strong $\delta_d-\alpha$ correlation and inapparent correlations between $\delta_r$ and three Band spectral parameters also suggest that the rise and decay phases of GRB pulses have different origins.; Comment: 29 pages...

‣ Ultra high energy cosmic rays: the highest energy frontier

Neto, João R. T. de Mello
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/10/2015 Português
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Ultra-high energy cosmic rays (UHECRs) are the highest energy messengers of the present universe, with energies up to $10^{20}$ eV. Studies of astrophysical particles (nuclei, electrons, neutrinos and photons) at their highest observed energies have implications for fundamental physics as well as astrophysics. The primary particles interact in the atmosphere and generate extensive air showers. Analysis of those showers enables one not only to estimate the energy, direction and most probable mass of the primary cosmic particles, but also to obtain information about the properties of their hadronic interactions at an energy more than one order of magnitude above that accessible with the current highest energy human-made accelerator. In this contribution we will review the state-of-the-art in UHECRs detection. We will present the leading experiments Pierre Auger Observatory and Telescope Array and discuss the cosmic ray energy spectrum, searches for directional anisotropy, studies of mass composition, the determination of the number of shower muons (which is sensitive to the shower hadronic interactions) and the proton-air cross section.; Comment: Prepared for the XIII International Workshop on Hadron Physics - March, 2015 - Rio de Janeiro...

‣ Energy dependence of barKN interactions and resonance pole of strange dibaryons

Ikeda, Yoichi; Kamano, Hiroyuki; Sato, Toru
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/04/2010 Português
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We study the resonance energy of the strange dibaryons using two models with the energy-independent and energy-dependent potentials for the s-wave barKN interaction, both of which are derived by certain reductions from the leading order term of the effective chiral Lagrangian. These potential models produce rather different off-shell behaviors of the two-body barKN - piSigma amplitudes in I=0 channel, i.e., the model with energy-independent (energy-dependent) potential predicts one (two) resonance pole in the Lambda(1405) region, while they describe the available data equally well. We find that the energy-independent potential model predicts one resonance pole of the strange dibaryons, whereas the energy-dependent potential model predicts two resonance poles: one is the shallow quasi-bound state of the barKNN, and another is the resonance of the piYN with large width. An investigation of the binding energy of the strange dibaryons will make a significant contribution to clarify resonance structure of s-wave barKN - piSigma around the Lambda(1405) region.; Comment: 6 pages, 6 figures.

‣ Performance of the CMS missing transverse energy reconstruction in pp data at sqrt(s) = 8 TeV

CMS Collaboration
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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The performance of missing transverse energy reconstruction algorithms is presented using sqrt(s) = 8 TeV proton-proton (pp) data collected with the CMS detector. Events with anomalous missing transverse energy are studied, and the performance of algorithms used to identify and remove these events is presented. The scale and resolution for missing transverse energy, including the effects of multiple pp interactions (pileup), are measured using events with an identified Z boson or isolated photon, and are found to be well described by the simulation. Novel missing transverse energy reconstruction algorithms developed specifically to mitigate the effects of large numbers of pileup interactions on the missing transverse energy resolution are presented. These algorithms significantly reduce the dependence of the missing transverse energy resolution on pileup interactions. Finally, an algorithm that provides an estimate of the significance of the missing transverse energy is presented, which is used to estimate the compatibility of the reconstructed missing transverse energy with a zero nominal value.; Comment: Replaced with published version. Added journal reference and DOI