Factorization and Resummation for Dijet Invariant Mass Spectra

Multijet cross sections at the LHC and Tevatron are sensitive to several distinct kinematic energy scales. When measuring the dijet invariant mass m_jj between two signal jets produced in association with other jets or weak bosons, m_jj will typically be much smaller than the total partonic center-of-mass energy Q, but larger than the individual jet masses m, such that there can be a hierarchy of scales m << m_jj << Q. This situation arises in many new-physics analyses at the LHC, where the invariant mass between jets is used to gain access to the masses of new-physics particles in a decay chain. At present, the logarithms arising from such a hierarchy of kinematic scales can only be summed at the leading-logarithmic level provided by parton-shower programs. We construct an effective field theory, SCET+, which is an extension of soft-collinear effective theory that applies to this situation of hierarchical jets. It allows for a rigorous separation of different scales in a multiscale soft function and for a systematic resummation of logarithms of both m_jj/Q and m/Q. As an explicit example, we consider the invariant mass spectrum of the two closest jets in e+e- -> 3 jets. We also give the generalization to pp -> N jets plus leptons relevant for the LHC.Comment: 37 pages, 6 figures; v2: journal versio

The Flow Regimes Associated with Hydraulic Fractured Horizontal Wells in Shale Formations

Shale gas in the United States went from a practically invisible resource to massive reserves that challenge the largest conventional gas accumulations in the world. Shale gas success is directly the result of economically managed deployment of petroleum technology, namely horizontal wells .Horizontal drilling and multi-stage stimulation technologies are driving the successful development of shale plays.;The production performance of hydraulically fractured horizontal wells in naturally fractured ultra-low permeability shale formations is not well established since the interaction among the hydraulic fractures, natural fracture system, and the shale matrix leads to a complex production mechanism that has not been fully investigated. Modeling and simulation of shale gas reservoir is challenging due to the complex nature of the reservoir, the strong heterogeneous and anisotropic characteristics of the system, different reservoir behavior, multiple gas-storage mechanisms and unique attributes that control the production.;The objective of this study was to understand the impact of hydraulic fracture on the flow behavior of the horizontal wells completed in ultralow permeability shale formations such as Marcellus Shale. A synthetic numerical model was developed using a commercial reservoir simulator (Eclipse) with different realizations to identify the impact of number of hydraulic fractures and gas desorption on the flow regime. Diagnostic plots were used to identify the flow regimes. The diagnostic plots were also used to investigate the impact of hydraulic fractures and shale characteristics on the duration of the flow periods. The most dominant flow regimes included the Early Linear Flow and Compounded Linear Flow. The detail investigation of the flow regimes revealed that as the number of hydraulic fracture increased, the duration of the Early Linear Flow became longer while the duration of the Compounded Linear Flow became shorter. Furthermore as the fracture half-length was reduced, the Early Linear Flow became shorter and the Compounded Linear Flow became longer. Also as the fissure permeability increased, the linear flow diminished

Jet p_T Resummation in Higgs Production at NNLL'+NNLO

We present predictions for Higgs production via gluon fusion with a p_T veto on jets and with the resummation of jet-veto logarithms at NNLL'+$NNLO order. These results incorporate explicit O(alphas^2) calculations of soft and beam functions, which include the dominant dependence on the jet radius R. In particular the NNLL' order accounts for the correct boundary conditions for the N3LL resummation, for which the only unknown ingredients are higher-order anomalous dimensions. We use scale variations in a factorization theorem in both rapidity and virtuality space to estimate the perturbative uncertainties, accounting for both higher fixed-order corrections as well as higher-order towers of jet-p_T logarithms. This formalism also predicts the correlations in the theory uncertainty between the exclusive 0-jet and inclusive 1-jet bins. At the values of R used experimentally, there are important corrections due to jet algorithm clustering that include logarithms of R. Although we do not sum logarithms of R, we do include an explicit contribution in our uncertainty estimate to account for higher-order jet clustering logarithms. Precision predictions for this H+0-jet cross section and its theoretical uncertainty are an integral part of Higgs analyses that employ jet binning.Comment: 24 pages, 11 figure

Retention of Low Income Children in Three Dental Studies Investigating Early Childhood Caries

Background: To our knowledge no dental studies have looked closely at subject retention, which is crucial to better understand oral health disparities. In this paper, we report retention rates and review and attempt to assess which retention strategies utilized in 3 dental research studies investigating ECC were effective for retaining WIC-enrolled children. The purpose of this paper is to discuss challenges that were encountered when working with these populations, describe characteristics of those not retained, and summarize some recommendations for future dental studies working at WIC sites. Methods: Three dental studies were conducted at WIC clinics in Iowa. Retention strategies focused on maintenance of contact over time, persistence in rescheduling appointments, utilization of incentives, high recruitment, and frequent communication with parents and program staff. Results: Retention rates in the studies ranged from 60 to 75 percent at the final research interventions. Studies were challenged by frequent moves of subjects, missed appointments, disconnected phones, busy schedules of parents, transportation problems, loss of child custody, family illness, and lack of interest. Those not retained in the studies were more likely to be younger, single, and less educated, with a lower household income and a non-Caucasian child. Lower retention was also associated with the presence of carious lesions. Conclusions: Despite many challenges, studies had good retention rates and benefited from the retention strategies. Future dental studies at WIC clinics may also benefit from arranging transportation, obtaining a free, 800 callback number, and offering after-hours appointments for working parents

Rapid soft X-ray fluctuations in solar flares observed with the X-ray polychromator

Three flares observed by the Soft X-Ray Polychromator on the Solar Maximum Mission were studied. Flare light curves from the Flat Crystal Spectrometer and Bent Crystal Spectrometer were examined for rapid signal variations. Each flare was characterized by an initial fast (less than 1 min) burst, observed by the Hard X-Ray Burst Spectrometer (HXRBS), followed by softer gradual X-ray emission lasting several minutes. From an autocorrelation function analysis, evidence was found for quasi-periodic fluctuations with rise and decay times of 10 s in the Ca XIX and Fe XXV light curves. These variations were of small amplitude (less than 20%), often coincided with hard X-ray emissions, and were prominent during the onset of the gradual phase after the initial hard X-ray burst. It is speculated that these fluctuations were caused by repeated energy injections in a coronal loop that had already been heated and filled with dense plasma associated with the initial hard X-ray burst

Genetic diversity among varieties and wild species accessions of pea (Pisum sativum L.) based on SSR markers

To assess the genetic relations inPisum genus and to examine putative duplicate accessions, 20 pea varieties (Pisum sativum L.) with 57 accessions from wild Pisum species fulvum, subspecies (subsp.) asiaticum, elatius, thebaicum, abyssinicum, transcaucasicum and arvense were analyzed using 10 out of 20 microsatellite primer pairs. We genotyped all accessions. In total, 59 alleles were identified in whole collection. The maximum number of alleles (8 alleles) was obtained from the PEACPLHPP, AF004843, and AA43090 loci. The maximum number of private alleles (4) in the wild collection was detected in AF004843 locus but in the cultivar collection, it was detected in AA430902 and PSBLOX13.2 loci. Cluster analysis and principal coordinate analysis located accessions in 3 groups and cultivated varieties were obviously separated from the wild accessions. Analysis of molecular variance (AMOVA) revealed that the intergroups component of variance (29%) is lower than the intragroups component of variance (71%). The lowest value of genetic differentiation ( Pisum genus and to examine putative duplicate accessions, 20 pea varieties (Pisum sativum L.) with 57 accessions from wild Pisum species fulvum, subspecies (subsp.) asiaticum, elatius, thebaicum, abyssinicum, transcaucasicum and arvense were analyzed using 10 out of 20 microsatellite primer pairs. We genotyped all accessions. In total, 59 alleles were identified in whole collection. The maximum number of alleles (8 alleles) was obtained from the PEACPLHPP, AF004843, and AA43090 loci. The maximum number of private alleles (4) in the wild collection was detected in AF004843 locus but in the cultivar collection, it was detected in AA430902 and PSBLOX13.2 loci. Cluster analysis and principal coordinate analysis located accessions in 3 groups and cultivated varieties were obviously separated from the wild accessions. Analysis of molecular variance (AMOVA) revealed that the intergroups component of variance (29%) is lower than the intragroups component of variance (71%). The lowest value of genetic differentiation (Pisum genus and to examine putative duplicate accessions, 20 pea varieties (Pisum sativum L.) with 57 accessions from wild Pisum species fulvum, subspecies (subsp.) asiaticum, elatius, thebaicum, abyssinicum, transcaucasicum and arvense were analyzed using 10 out of 20 microsatellite primer pairs. We genotyped all accessions. In total, 59 alleles were identified in whole collection. The maximum number of alleles (8 alleles) was obtained from the PEACPLHPP, AF004843, and AA43090 loci. The maximum number of private alleles (4) in the wild collection was detected in AF004843 locus but in the cultivar collection, it was detected in AA430902 and PSBLOX13.2 loci. Cluster analysis and principal coordinate analysis located accessions in 3 groups and cultivated varieties were obviously separated from the wild accessions. Analysis of molecular variance (AMOVA) revealed that the intergroups component of variance (29%) is lower than the intragroups component of variance (71%). The lowest value of genetic differentiation (PT = 0.27) of pair wise collections between wild and variety collections, was detected in ssp. elatius. Assignment test on the basis of log-likelihood to estimate the likelihood that an individual belongs to a given group, showed that 96% of accessions being assigned correctly to their groups. This study showed that genetic probability profiles of accessions can corroborate clustering analyses while providing additional information as a powerful tool for assigning accessions into their related groups

Hard X-ray and UV Observations of the 2005 January 15 Two-ribbon Flare

In this paper, we present comprehensive analysis of a two-ribbon flare observed in UV 1600{\AA} by Transition Region and Coronal Explorer and in HXRs by Reuven Ramaty High Energy Solar Spectroscopic Imager. HXR (25-100 keV) imaging observations show two kernels of size (FWHM) 15?? moving along the two UV ribbons. We find the following results. (1) UV brightening is substantially enhanced wherever and whenever the compact HXR kernel is passing, and during the HXR transit across a certain region, the UV count light curve in that region is temporally correlated with the HXR total flux light curve. After the passage of the HXR kernel, the UV light curve exhibits smooth monotonical decay. (2)We measure the apparent motion speed of the HXR sources and UV ribbon fronts, and decompose the motion into parallel and perpendicular motions with respect to the magnetic polarity inversion line (PIL). It is found that HXR kernels and UV fronts exhibit similar apparent motion patterns and speeds. The parallel motion dominates during the rise of the HXR emission, and the perpendicular motion starts and dominates at the HXR peak, the apparent motion speed being 10-40 km s-1. (3) We also find that UV emission is characterized by a rapid rise correlated with HXRs, followed by a long decay on timescales of 15-30 minutes. The above analysis provides evidence that UV brightening is primarily caused by beam heating, which also produces thick-target HXR emission. The thermal origin of UV emission cannot be excluded, but would produce weaker heating by one order of magnitude. The extended UV ribbons in this event are most likely a result of sequential reconnection along the PIL, which produces individual flux tubes (post-flare loops), subsequent non-thermal energy release and heating in these flux tubes, and then the very long cooling time of the transition region at the feet of these flux tubes.Comment: 8 figure

Quantum reflection of atoms from a solid surface at normal incidence

We observed quantum reflection of ultracold atoms from the attractive potential of a solid surface. Extremely dilute Bose-Einstein condensates of ^{23}Na, with peak density 10^{11}-10^{12}atoms/cm^3, confined in a weak gravito-magnetic trap were normally incident on a silicon surface. Reflection probabilities of up to 20 % were observed for incident velocities of 1-8 mm/s. The velocity dependence agrees qualitatively with the prediction for quantum reflection from the attractive Casimir-Polder potential. Atoms confined in a harmonic trap divided in half by a solid surface exhibited extended lifetime due to quantum reflection from the surface, implying a reflection probability above 50 %.Comment: To appear in Phys. Rev. Lett. (December 2004)5 pages, 4 figure

Isonitrile-responsive and bioorthogonally removable tetrazine protecting groups.

In vivo compatible reactions have a broad range of possible applications in chemical biology and the pharmaceutical sciences. Here we report tetrazines that can be removed by exposure to isonitriles under very mild conditions. Tetrazylmethyl derivatives are easily accessible protecting groups for amines and phenols. The isonitrile-induced removal is rapid and near-quantitative. Intriguingly, the deprotection is especially effective with (trimethylsilyl)methyl isocyanide, and serum albumin can catalyze the elimination under physiological conditions. NMR and computational studies revealed that an imine-tautomerization step is often rate limiting, and the unexpected cleavage of the Si-C bond accelerates this step in the case with (trimethylsilyl)methyl isocyanide. Tetrazylmethyl-removal is compatible with use on biomacromolecules, in cellular environments, and in living organisms as demonstrated by cytotoxicity experiments and fluorophore-release studies on proteins and in zebrafish embryos. By combining tetrazylmethyl derivatives with previously reported tetrazine-responsive 3-isocyanopropyl groups, it was possible to liberate two fluorophores in vertebrates from a single bioorthogonal reaction. This chemistry will open new opportunities towards applications involving multiplexed release schemes and is a valuable asset to the growing toolbox of bioorthogonal dissociative reactions

X ray spectra of X Per

The cosmic X-ray spectroscopy experiment on OSO-8 observed X Per for twenty days during two observations in Feb. 1976 and Feb. 1977. The spectrum of X Per varies in phase with its 13.9 min period, hardening significantly at X-ray minimum. Unlike other X-ray binary pulsar spectra, X Per's spectra do not exhibit iron line emission or strong absorption features. The data show no evidence for a 22 hour periodicity in the X-ray intensity of X Per. These results indicate that the X-ray emission from X Per may be originating from a neutron star in a low density region far from the optically identified Be star