118648061
ObservingCPviolation in many-body decays
It is well known that observing $CP$ violation in many-body decays could provide strong evidence for physics beyond the standard model. Many searches have been carried out; however, no $5\ensuremath{\sigma}$ evidence for $CP$ violation has yet been found in these types of decays. A novel model-independent method for observing $CP$ violation in many-body decays is presented in this paper. It is shown that the sensitivity of this method is significantly larger than those used to-date.
209834699
Analysis of the resonant components in B¯º → J/ ψπ+π-
Interpretation of CP violation measurements using charmonium decays, in both the B¯o and B¯os systems, can be subject to changes due to "penguin" type diagrams. These effects can be investigated using measurements of the Cabibbo-suppressed B¯o → J/ ψπ+π- decays. The final state composition of this channel is investigated using a 1.0 fb(-1) sample of data produced in 7 TeV pp collisions at the LHC and collected by the LHCb experiment. A modified Dalitz-plot analysis is performed using both the invariant mass spectra and the decay angular distributions. An improved measurement of the B¯o → J/ ψπ+π- branching fraction of (3.97 ± 0.09 ± 0.11 ± 0.16) x 10(-5) is reported where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty of the branching fraction of the decay B¯ → J/ ψ K¯ used as a normalization channel. Significant production of fₒ(500) and ρ(770) resonances is found in the substructure of the J/ ψπ+π- final state, and this indicates that they are viable final states for CP violation studies. In contrast evidence for the fₒ(980) resonance is not found. This allows us to establish the first upper limit on the branching fraction product Β(B¯o → J/ ψfₒ (980)) x Β(fₒ(980) → π+π- < 1.1 x 10(-6), leading to an upper limit on the absolute value of the mixing angle of the fₒ(980) with the fₒ(500) of less than 31°, both at 90% confidence level.
18677949
Separating Signals from Non-Interfering Backgrounds using Probabilistic Event Weightings
A common situation in experimental physics is to have a signal which can not be separated from a non-interfering background through the use of any cut. In this paper, we describe a procedure for determining, on an event-by-event basis, a quality factor (Q-factor) that a given event originated from the signal distribution. This Q-factor can then be used as an event weight in subsequent analysis procedures, allowing one to more directly access the true spectrum of the signal.
119112453
How good are your fits? Unbinned multivariate goodness-of-fit tests in high energy physics
Multivariate analyses play an important role in high energy physics. Such analyses often involve performing an unbinned maximum likelihood fit of a probability density function (p.d.f.) to the data. This paper explores a variety of unbinned methods for determining the goodness of fit of the p.d.f. to the data. The application and performance of each method is discussed in the context of a real-life high energy physics analysis (a Dalitz-plot analysis). Several of the methods presented in this paper can also be used for the non-parametric determination of whether two samples originate from the same parent p.d.f. This can be used, e.g., to determine the quality of a detector Monte Carlo simulation without the need for a parametric expression of the efficiency.
108512977
Distributed analysis at LHCb
The distributed analysis experience to date at LHCb has been positive: job success rates are high and wait times for high-priority jobs are low. LHCb users access the grid using the GANGA job-management package, while the LHCb virtual organization manages its resources using the DIRAC package. This clear division of labor has benefitted LHCb and its users greatly; it is a major reason why distributed analysis at LHCb has been so successful. The newly formed LHCb distributed analysis support team has also proved to be a success.
118830218
Prospects for the measurement of the unitarity triangle angle gamma from B-0 -> DK+pi(-) decays
The potential for a precise measurement of the unitarity triangle angle gamma in future experiments from the decay B-0 -> DK*0 is well known. It has recently been suggested that the sensitivity can be significantly enhanced by analyzing the B-0 -> DK+pi(-) Dalitz plot to extract amplitudes relative to those of the flavor-specific decay B-0 -> D2*-K+. An extension to this method which includes the case where the neutral D meson is reconstructed in suppressed final states is presented. The sensitivity to gamma is estimated using this method and compared to that obtained using the B-0 -> DK*0 decay alone. Experimental effects, such as background contamination, are also considered. This approach appears to be a highly attractive addition to the family of methods that can be used to determine gamma.
117248378
Accidental Supersymmetry and the Naturalness of Codimension-2 Branes
This thesis addresses two separate naturalness issues which generically come to bear on physical theories with large extra dimensions, and so a gravity scale much lower than the Planck scale. The first is related to the observed stability of the proton, wherein we determine the relevant constraints on an additional gauge boson which conserves baryon number. Although several such proposals have been previously considered, our analysis is distinctive in its interest in lighter gauge boson masses (which naturally arise in such models), and in its focus on the dependence of constraints due to kinetic mixing effects. The second is related to the main purpose of large extra dimensions—namely, to address the smallness of the observed vacuum energy—wherein we compute the leading-order quantum corrections to the four-dimensional (4D) vacuum energy resulting from loops of extradimensional fields. We compute the contributions from bulk scalars (spin 0), fermions (spin 12 ), and gauge fields (spin 1) in a flux-stabilized, spheroidal extra-dimensional geometry whose rugbyball shape is due to two codimension-2 branes—one at each pole. (We also obtain the corresponding beta functions for both bulk and brane operators.) These results are then combined to obtain the net contribution from various multiplets in the context of a particular supersymmetric extra-dimensional model that has been shown to give a vanishing result for the 4D vacuum energy at the classical level. Surprisingly, we find that supersymmetry can be preserved dynamically at one loop in the case of identical branes, without arranging any particular relationship between the brane parameters. Perturbing away from the case of identical branes is shown to give a positive 1-loop contribution to the 4D vacuum energy whose size is set by the radius of the extra dimensions.
118732841
Running with rugby balls: bulk renormalization of codimension-2 branes
A bstractWe compute how one-loop bulk effects renormalize both bulk and brane effective interactions for geometries sourced by codimension-two branes. We do so by explicitly integrating out spin-zero, -half and -one particles in 6-dimensional Einstein-Maxwell-Scalar theories compactified to 4 dimensions on a flux-stabilized 2D geometry. (Our methods apply equally well for D dimensions compactified to D − 2 dimensions, although our explicit formulae do not capture all divergences when D > 6.) The renormalization of bulk interactions are independent of the boundary conditions assumed at the brane locations, and reproduce standard heat-kernel calculations. Boundary conditions at any particular brane do affect how bulk loops renormalize this brane’s effective action, but not the renormalization of other distant branes. Although we explicitly compute our loops using a rugby ball geometry, because we follow only UV effects our results apply more generally to any geometry containing codimension-two sources with conical singularities. Our results have a variety of uses, including calculating the UV sensitivity of one-loop vacuum energy seen by observers localized on the brane. We show how these one-loop effects combine in a surprising way with bulk back-reaction to give the complete low-energy effective cosmological constant, and comment on the relevance of this calculation to proposed applications of codimension-two 6D models to solutions of the hierarchy and cosmological constant problems.
3581209
EFT beyond the horizon: stochastic inflation and how primordial quantum fluctuations go classical
A bstractWe identify the effective field theory describing the physics of super-Hubble scales and show it to be a special case of a class of effective field theories appropriate to open systems. Open systems are those that allow information to be exchanged between the degrees of freedom of interest and those that are integrated out, such as would be appropriate for particles moving through a fluid. Strictly speaking they cannot in general be described by an effective lagrangian; rather the appropriate ‘low-energy’ limit is instead a Lindblad equation describing the time-evolution of the density matrix of the slow degrees of freedom. We derive the equation relevant to super-Hubble modes of quantum fields in de Sitter (and near-de Sitter) spacetimes and derive two of its implications. We show that the evolution of the diagonal density-matrix elements quickly approach the Fokker-Planck equation of Starobinsky’s stochastic inflationary picture. This allows us both to identify the leading corrections and provide an alternative first-principles derivation of this picture’s stochastic noise and drift. (As applications we show that the noise for massless fields is independent of the details of the window function used, and also compute how the noise changes for systems with a sub-luminal speed of sound, cs< 1.) We then argue that the presence of interactions drive the off-diagonal density-matrix elements to zero in the field
118294173
A measurement of the inclusive branching ratio for $b o sgamma$ with the ALEPH detector at LEP
118827257
Who you gonna call? Runaway ghosts, higher derivatives and time-dependence in EFTs
A bstractWe briefly review the formulation of effective field theories (EFTs) in timedependent situations, with particular attention paid to their domain of validity. Our main interest is the extent to which solutions of the EFT capture the dynamics of the full theory. For a simple model we show by explicit calculation that the low-energy action obtained from a sensible UV completion need not take the restrictive form required to obtain only secondorder field equations, and we clarify why runaway solutions are nevertheless typically not a problem for the EFT. Although our results will not be surprising to many, to our knowledge they are only mentioned tangentially in the EFT literature, which (with a few exceptions) largely addresses time-independent situations.