14771068
Soft Collinear Effective Theory: An Overview
In this talk I give an overview of soft collinear effective theory (SCET), including a discussion of some recent advances. First, I briefly cover the foundation upon which SCET is built, namely QCD factorization, and review the theoretical framework of SCET. Next, I cover some recent calculations involving SCET. Since there are more interesting results than I can cover, I have picked four that that I find particularly exciting. The first two topics are dynamical threshold enhancements in Drell-Yan and resummation of higgs production at the LHC. Both topics center on the resummation of large Sudakov logarithms, however, for each there is a twist. In the case of threshold enhancements in Drell-Yan, it is partonic, not hadronic logarithms that are summed. In the case of higgs production at the LHC, the twist is that the logarithms are of a time-like scale. The third topic highlighted is electroweak corrections at high energy. In particular the electroweak Sudakov form factor. Finally, I end by discussing generalized event shapes in e+e− annihilation.
14211746
Power counting and effective field theory for charmonium
We hypothesize that the correct power counting for charmonia is in the parameter {Lambda}{sub QCD}/m{sub c}, but is not based purely on dimensional analysis (as is heavy quark effective theory). This power counting leads to predictions which differ from those resulting from the usual velocity power counting rules of non-relativistic QCD (NRQCD). In particular, we show that while {Lambda}{sub QCD}/m{sub c} power counting preserves the empirically verified predictions of spin symmetry in decays, it also leads to new predictions which include a hierarchy between spin singlet and triplet octet matrix elements in the J/{psi} system, a quenching of the net polarization in production at large transverse momentum, and no end point enhancement in radiative decays. We discuss explicit tests which can differentiate between the traditional and new theories of NRQCD.
120287775
Extending theSTUFormalism for Electroweak Oblique Corrections to the Case of Light New Physics
Abstract The STU formalism, which parametrizes oblique electroweak corrections due to heavy new physics, has recently been extended to the case of light new physics. In principle, this extended formalism, which involves the six parameters STUVWX , must be used if loop contributions to the oblique corrections entail light new particles with masses in the range ∼ M Z or less. Applying classical equations of motion to manipulate the effective lagrangian, we present here a thorough introductory discussion of the STUVWX formalism, elucidating such subtleties as the connection between S − X and the star formalism of Kennedy and Lynn, the connection between S − X , and the e parameters of Altarelli and Barbieri, and the loss of definite symmetry properties which S and U undergo as the STU parameter set is extended to the case of light new physics. This paper provides a significantly more detailed, expanded, and pedagogic presentation than previous expositions of the STUVWX parameters.
118168769
The N N scattering 3S1 - 3D1 mixing angle at NNLO
The 3S1-3D1 mixing angle for nucleon-nucleon scattering, epsilon_1, is calculated to next-to-next-to-leading order in an effective field theory with perturbative pions. Without pions, the low energy theory fits the observed epsilon_1 well for momenta less than $\sim 50$ MeV. Including pions perturbatively significantly improves the agreement with data for momenta up to $\sim 150$ MeV with one less parameter. Furthermore, for these momenta the accuracy of our calculation is similar to an effective field theory calculation in which the pion is treated non-perturbatively. This gives phenomenological support for a perturbative treatment of pions in low energy two-nucleon processes. We explain why it is necessary to perform spin and isospin traces in d dimensions when regulating divergences with dimensional regularization in higher partial wave amplitudes.
117895382
Exclusive Radiative Decays of Upsilon in SCET
We study exclusive radiative decays of the $\Upsilon$ using soft-collinear effective theory and non-relativistic QCD. In contrast to inclusive radiative decays at the endpoint we find that color-octet contributions are power suppressed in exclusive decays, and can safely be neglected, greatly simplifying the analysis. We determine the complete set of Lorentz structures that can appear in the SCET Wilson coefficients and match onto them using results from a previous calculation. We run these coefficients from the scale $\mups$ to the scale $\Lambda \sim 1 \textrm{GeV}$, thereby summing large logarithms. Finally we use our results to predict the ratio of branching fractions $B(\Upsilon \to \gamma f_2)/B(J/\psi \to \gamma f_2)$, $B(J/\psi \to \gamma f_2)/B(\psi' \to \gamma f_2)$, and the partial rate for $\Upsilon \to \gamma \pi \pi$.
56195115
Doubly Heavy Baryons, Heavy Quark-DiQuark Symmetry and NRQCD
In the heavy quark limit, properties of heavy mesons and doubly heavy baryons are related by heavy quark-diquark symmetry. This problem is reanalyzed in the framework of Non-Relativistic QCD (NRQCD). We introduce a novel method for deriving Potential NRQCD (pNRQCD) Lagrangians for composite fields from vNRQCD, which contains quarks and antiquarks as explicit degrees of freedom and maintains manifest power counting in the velocity via a label formalism. A Hubbard-Stratonovich transformation is used to eliminate four quark interactions in vNRQCD and then quarks and antiquarks are integrated out to get effective Lagrangians for composite fields. This method is used to rederive Lagrangians for the Q ¯
16972795
The XO Project: Searching for Transiting Extrasolar Planet Candidates
The XO project’s first objective is to find hot Jupiters transiting bright stars, i.e. V < 12, by precision differential photometry. Two XO cameras have been operating since September 2003 on the 10,000-foot Haleakala summit on Maui. Each XO camera consists of a 200-mm f/1.8 lens coupled to a 1024x1024 pixel, thinned CCD operated by drift scanning. In its first year of routine operation, XO has observed 6.6% of the sky, within six 7 ◦ -wide strips scanned from 0 ◦ to +63 ◦ of declination and centered at RA=0, 4, 8, 12, 16, and 20 hours. Autonomously operating, XO records 1 billion pixels per clear night, calibrates them photometrically and astrometrically, performs aperture photometry, archives the pixel data and transmits the photometric data to STScI for further analysis. From the first year of operation, the resulting database consists of photometry of �100,000 stars at more than 1000 epochs per star with differential photometric precision better than 1% per epoch. Analysis of the light curves of those stars produces transiting-planet candidates requiring detailed follow up, described elsewhere, culminating in spectroscopy to measure radial-velocity variation in order to differentiate genuine planets from the more numerous impostors, primarily eclipsing binary and multiple stars.
38052681
Eclipsing Binary Science via the Merging of Transit and Doppler Exoplanet Survey Data—A Case Study with the MARVELS Pilot Project and SuperWASP
Exoplanet transit and Doppler surveys discover many binary stars during their operation that can be used to conduct a variety of ancillary science. Specifically, eclipsing binary stars can be used to study the stellar mass-radius relationship and to test predictions of theoretical stellar evolution models. By cross-referencing 24 binary stars found in the MARVELS Pilot Project with SuperWASP photometry, we find two new eclipsing binaries, TYC 0272-00458-1 and TYC 1422-01328-1, which we use as case studies to develop a general approach to eclipsing binaries in survey data. TYC 0272-00458-1 is a single-lined spectroscopic binary for which we calculate a mass of the secondary and radii for both components using reasonable constraints on the primary mass through several different techniques. For a primary mass of M_1 = 0.92 ± 0.1 M_☉, we find M_2 = 0.610 ± 0.036 M_☉, R_1 = 0.932 ± 0.076 R_☉, and R_2 = 0.559 ± 0.102 R_☉, and find that both stars have masses and radii consistent with model predictions. TYC 1422-01328-1 is a triple-component system for which we can directly measure the masses and radii of the eclipsing pair. We find that the eclipsing pair consists of an evolved primary star (M_1 = 1.163 ± 0.034 M_☉, R_1 = 2.063 ± 0.058 R_☉) and a G-type dwarf secondary (M_2 = 0.905 ± 0.067 M_☉, R_2 = 0.887 ± 0.037 R_☉). We provide the framework necessary to apply this analysis to much larger data sets.
17485541
MEASURING STELLAR RADIAL VELOCITIES WITH A DISPERSED FIXED-DELAY INTERFEROMETER
We demonstrate the ability to measure precise stellar barycentric radial velocities with the dispersed fixed-delay interferometer technique using the Exoplanet Tracker (ET), an instrument primarily designed for precision differential Doppler velocity measurements using this technique. Our barycentric radial velocities, derived from observations taken at the KPNO 2.1 m telescope, differ from those of Nidever et al. by 0.047 km s−1 (rms) when simultaneous iodine calibration is used, and by 0.120 km s−1 (rms) without simultaneous iodine calibration. Our results effectively show that a Michelson interferometer coupled to a spectrograph allows precise measurements of barycentric radial velocities even at a modest spectral resolution of R ~ 5100. A multiobject version of the ET instrument capable of observing ~500 stars per night is being used at the Sloan 2.5 m telescope at Apache Point Observatory for the Multiobject APO Radial Velocity Exoplanet Large-area Survey (MARVELS), a wide-field radial velocity survey for extrasolar planets around TYCHO-2 stars in the magnitude range 7.6 < V < 12. In addition to precise differential velocities, this survey will also yield precise barycentric radial velocities for many thousands of stars using the data analysis techniques reported here. Such a large kinematic survey at high velocity precision will be useful in identifying the signature of accretion events in the Milky Way and understanding local stellar kinematics, in addition to discovering exoplanets, brown dwarfs, and spectroscopic binaries.
5757747
Detecting ‘Temperate’ Jupiters: the prospects of searching for transiting gas giants in Habitable Zones
Wide-field photometric surveys in search of transiting extrasolar planets are now numerous and have met with some success in finding hot Jupiters. These transiting planets have very short periods and very small semimajor axes, facilitating their discovery in such surveys. Transiting planets with longer periods present more of a challenge, since they transit their parent stars less frequently. This paper investigates the effects of observing windows on detecting transiting planets by calculating the fraction of planets with a given period that have zero, one (single), two (double), or ≥3 (multiple) transits occurring while observations are being taken. We also investigate the effects of collaboration by performing the same calculations with combined observing times from two wide-field transit survey groups. For a representative field of the 2004 observing season, both XO and SuperWASP experienced an increase in single and double transit events by up to 20–40 per cent for planets with periods 14 < P < 150 d when collaborating by sharing data. For the XO Project using its data alone, between 20–40 per cent of planets with periods 14–150 d should have been observed at least once. For the SuperWASP Project, 50–90 per cent of planets with periods between 14–150 d should have been observed at least once. If XO and SuperWASP combine their observations, 50–100 per cent of planets with periods less than 20 d should be observed three or more times. We find that in general wide-field transit surveys have selected appropriate observing strategies to observe a significant fraction of transiting giant planets with semimajor axes larger than the hot Jupiter regime. The actual number of intermediate-period transiting planets that are detected depends upon their true semimajor axis distribution and the signal-to-noise ratio of the data. We therefore conclude that the investment of resources needed to investigate more sophisticated photometry calibrations or examine single and double transit events from wide-field surveys might be a worthwhile endeavour. The collaboration of different transit surveys by combining photometric data can greatly increase the number of transits observed for all semimajor axes. In addition, the increased number of data points can improve the signal-to-noise ratio of binned data, increasing the chances of detecting transiting extrasolar planets.
118446053
The Metallicity of the CM Draconis System
The CM Draconis system comprises two eclipsing mid-M dwarfs of nearly equal mass in a 1.27?day orbit. This well-studied eclipsing binary has often been used for benchmark tests of stellar models, since its components are among the lowest mass stars with well-measured masses and radii ( 1% relative precision). However, as with many other low-mass stars, non-magnetic models have been unable to match the observed radii and effective temperatures for CM Dra at the 5%-10% level. To date, the uncertain metallicity of the system has complicated comparison of theoretical isochrones with observations. In this Letter, we use data from the SpeX instrument on the NASA Infrared Telescope Facility to measure the metallicity of the system during primary and secondary eclipses, as well as out of eclipse, based on an empirical metallicity calibration in the H and K near-infrared (NIR) bands. We derive an [Fe/H] = -0.30 ? 0.12 that is consistent across all orbital phases. The determination of [Fe/H] for this system constrains a key dimension of parameter space when attempting to reconcile model isochrone predictions and observations.