31,082 research outputs found
Soft-Collinear Messengers: A New Mode in Soft-Collinear Effective Theory
It is argued that soft-collinear effective theory for processes involving
both soft and collinear partons, such as exclusive B-meson decays, should
include a new mode in addition to soft and collinear fields. These
"soft-collinear messengers" can interact with both soft and collinear particles
without taking them far off-shell. They thus can communicate between the soft
and collinear sectors of the theory. The relevance of the new mode is
demonstrated with an explicit example, and the formalism incorporating the
corresponding quark and gluon fields into the effective Lagrangian is
developed.Comment: 22 pages, 5 figures. Extended Section 6, clarifying the relevance of
different types of soft-collinear interaction
Phase Transitions in a Two-Component Site-Bond Percolation Model
A method to treat a N-component percolation model as effective one component
model is presented by introducing a scaled control variable . In Monte
Carlo simulations on , , and simple cubic
lattices the percolation threshold in terms of is determined for N=2.
Phase transitions are reported in two limits for the bond existence
probabilities and . In the same limits, empirical formulas
for the percolation threshold as function of one
component-concentration, , are proposed. In the limit a new
site percolation threshold, , is reported.Comment: RevTeX, 5 pages, 5 eps-figure
A proof of factorization for B -> D pi
We prove that the matrix elements of four fermion operators mediating the
decay B^0 -> D^+ \pi^- and B^- -> D^0 \pi^- factor into the product of a form
factor describing the B -> D transition and a convolution of a short distance
coefficient with the nonperturbative pion light-cone wave function. This is
shown to all orders in alpha_s, up to corrections suppressed by factors of
1/mb, 1/mc, and 1/E_pi. It is not necessary to assume that the pion state is
dominated by the q-qbar Fock state.Comment: 4 pages, 3 figs, PRL versio
Abnormal Perceptual Sensitivity in Body-Focused Repetitive Behaviors
Objective Several compulsive grooming habits such as hair pulling, skin picking, and nail biting are collectively known as body-focused repetitive behaviors (BFRBs). Although subclinical BFRBs are common and benign, more severe and damaging manifestations exist that are difficult to manage. Researchers have suggested that BFRBs are maintained by various cognitive, affective, and sensory contingencies. Although the involvement of cognitive and affective processes in BFRBs has been studied, there is a paucity of research on sensory processes. Methods The current study tested whether adults with subclinical or clinical BFRBs would report abnormal patterns of sensory processing as compared to a healthy control sample. Results Adults with clinical BFRBs (n = 26) reported increased sensory sensitivity as compared to persons with subclinical BFRBs (n = 48) and healthy individuals (n = 33). Elevations in sensation avoidance differentiated persons with clinical versus subclinical BFRBs. Sensation seeking patterns were not different between groups. Unexpectedly, BFRB severity was associated with lower registration of sensory stimuli, but this finding may be due to high psychiatric comorbidity rates in the BFRB groups. Conclusions These findings suggest that several sensory abnormalities may underlie BFRBs. Implications for the etiology and treatment of BFRBs are discussed
Power Counting in the Soft-Collinear Effective Theory
We describe in some detail the derivation of a power counting formula for the
soft-collinear effective theory (SCET). This formula constrains which operators
are required to correctly describe the infrared at any order in the
Lambda_QCD/Q expansion (lambda expansion). The result assigns a unique
lambda-dimension to graphs in SCET solely from vertices, is gauge independent,
and can be applied independent of the process. For processes with an OPE the
lambda-dimension has a correspondence with dynamical twist.Comment: 12 pages, 1 fig, journal versio
Application of Computer Axial Tomography (CAT) to measuring crop canopy geometry
The feasibility of using the principles of computer axial topography (CAT) to quantify the structure of crop canopies was investigated because six variables are needed to describe the position-orientation with time of a small piece of canopy foliage. Several cross sections were cut through the foliage of healthy, green corn and soybean canopies in the dent and full pod development stages, respectively. A photograph of each cross section representing the intersection of a plane with the foliage was enlarged and the air-foliage boundaries delineated by the plane were digitized. A computer program was written and used to reconstruct the cross section of the canopy. The approach used in applying optical computer axial tomography to measuring crop canopy geometry shows promise of being able to provide needed geometric information for input data to canopy reflectance models. The difficulty of using the CAT scanner to measure large canopies of crops like corn is discussed and a solution is proposed involving the measurement of plants one at a time
Emotion Regulation Deficits in Persons with Body-Focused Repetitive Behavior Disorders
Background
Conceptualizations of emotion dysregulation (ED) and body-focused repetitive behavior disorders (BFRBDs) imply that ED may be a central component of BFRBDs as well as a factor that distinguishes BFRBDs from non-impairing, subclinical body-focused repetitive behaviors (BFRBs). The current study empirically tested these observations.
Methods
One hundred thirty-eight undergraduates (of 1900 who completed a screening survey) completed self-report measures assessing four emotion regulation (ER) deficits hypothesized to underlie ED (alexithymia, maladaptive emotional reactivity, experiential avoidance, and response inhibition when distressed); 34 of these participants had BFRBDs, 64 had subclinical BFRBs, and 42 were unaffected by BFRBs.
Results
Results indicated that participants with BFRBDs reported higher levels of maladaptive emotional reactivity, experiential avoidance, and response inhibition when distressed than participants with subclinical BFRBs and participants unaffected by BFRBs. These results held even when controlling for comorbidity and total number of reported BFRBs. Participants did not differ on alexithymia.
Limitations
Limitations of the current study include the BFRB groups’ different distributions of BFRB types (e.g., hair pulling versus skin picking), the sample\u27s demographic uniformity, and the fact that negative affectivity was not controlled when exploring BFRB group differences on ER deficits. Future research should improve on these limitations.
Conclusions
The current results suggest that ED is a factor that differentiates BFRBDs from subclinical BFRBs. Such results may be useful for generating hypotheses regarding mechanisms responsible for BFRBs’ development into BFRBDs. Furthermore, these results may provide insight into factors that explain the efficacy of more contemporary behavioral treatments for BFRBDs
Crossover from Single-Ion to Coherent Non-Fermi Liquid Behavior in CeLaNiGe
We report specific heat and magneto-resistance studies on the compound
CeLaNiGe for various concentrations over the entire
stoichiometric range. Our data reveal single-ion scaling with Ce-concentration
between and 0.95. Furthermore, CeNiGe turns out to have
the largest ever recorded value of the electronic specific heat 5.5 J at K which was found in Cerium
f-electron lattice systems. In the doped samples increases
logarithmically in the temperature range between 3 K and 50 mK typical for
non-Fermi liquid (nFl) behavior, while exhibits a Kondo-like minimum
around 30 K, followed by a single-ion local nFl behavior. In contrast to this,
CeNiGe flattens out in below 300 mK and displays a
pronounced maximum in the resistivity curve at 1.5 K indicating a coherent
heavy fermion groundstate. These properties render the compound
CeLaNiGe a unique system on the borderline between
Fermi liquid and nFl physics.Comment: 2 pages, 3 figures, SCES0
Shape-Function Effects and Split Matching in B-> Xs l+ l-
We derive the triply differential spectrum for the inclusive rare decay B ->
Xs l+ l- in the shape function region, in which Xs is jet-like with . Experimental cuts make this a relevant region. The
perturbative and non-perturbative parts of the matrix elements can be defined
with the Soft-Collinear Effective Theory, which is used to incorporate alphas
corrections consistently. We show that, with a suitable power counting for the
dilepton invariant mass, the same universal jet and shape functions appear as
in B-> Xs gamma and B-> Xu l nu decays. Parts of the usual alphas(m_b)
corrections go into the jet function at a lower scale, and parts go into the
non-perturbative shape function. For B -> Xs l+ l-, the perturbative series in
alphas are of a different character above and below mu=mb. We introduce a
``split matching'' method that allows the series in these regions to be treated
independently.Comment: 33 pages; journal versio
Size Matters: Origin of Binomial Scaling in Nuclear Fragmentation Experiments
The relationship between measured transverse energy, total charge recovered
in the detector, and size of the emitting system is investigated. Using only
very simple assumptions, we are able to reproduce the observed binomial
emission probabilities and their dependences on the transverse energy.Comment: 14 pages, including 4 figure
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