118268350
Laser wakefield acceleration of electrons at Ecole Polytechnique
The acceleration of electrons injected in a plasma wave generated by the laser wakefield mechanism has been observed. A maximum energy gain of 1.6 MeV has been measured and the maximum longitudinal electric field is estimated to 1.5 GV/m. The experimental data agree with theoretical predictions when 3D effects are taken into account. The duration of the plasma wave inferred from the number of accelerated electrons is of the order of 1 ps.
125343210
Measurement of the CKM matrix element $|V_{ub}|$ with $B \to \rho e \nu$ decays
120104270
Operation of the Cherenkov detector DIRC of BABAR at high luminosity
The DIRC (acronym for Detection of Internally Reflected Cherenkov (light)) is the ring imaging Cherenkov detector of the BABAR detector at the PEP-II ring of SLAC. It provides the identification of pions, kaons and protons for momenta up to 4 GeV/c with high efficiency. This is needed to reconstruct CP-violating B-decay final states and to provide B-meson flavour tagging for time dependent asymmetry measurements. The DIRC radiators consists of long rectangular bars made of synthetic fused silica and the photon detector is a water tank equipped with an array of 10.752 conventional photomultipliers. At the end of the year 2000 BABAR has recorded about 22 million B~B pairs reaching the design luminosity of L=3/spl middot/10/sup 33//cm/sup 2/s. The ability to keep the beam background level low at highest collision rates and the long term reliability of the DIRC components during continuous data taking are requirements of BABAR to accomplish its physics program.
202048438
Branching fraction for $B^{+} \to \pi^0 \ell^{+} \nu$, measured in $\upsilon_{4S} \to B \bar{B}$ events tagged by $B^{-} \to D^0 \ell^{-}$ anti-v ($X$) decays
160033287
Improved Measurement of CP Violation in Neutral B Decays to c cs
126404399
Measurements of branching fractions and CP-violating asymmetries in B-meson decays to the charmless two-body states K0 pi+, anti-K0 K+, and K0 anti-K0
119210548
Scrutinizing the Cosmological Constant Problem and a possible resolution
We suggest a new perspective on the Cosmological Constant Problem by scrutinizing its standard formulation. In classical and quantum mechanics without gravity, there is no definition of the zero point of energy. Furthermore, the Casimir effect only measures how the vacuum energy {\it changes} as one varies a geometric modulus. This leads us to propose that the physical vacuum energy in a Friedman-Lema\^itre-Robertson-Walker expanding universe only depends on the time variation of the scale factor $a(t)$. Equivalently, requiring that empty Minkowski space is gravitationally stable is a principle that fixes the ambiguity in the zero point energy. On the other hand, if there is a meaningful bare cosmological constant, this prescription should be viewed as a fine-tuning. 
We describe two different choices of vacuum, one of which is consistent with the current universe consisting only of matter and vacuum energy. The resulting vacuum energy density $\rhovac$ is constant in time and approximately $k_c^2 H_0^2$, where $k_c$ is a momentum cut-off and $H_0$ is the current Hubble constant; for a cut-off close to the Planck scale, values of $\rhovac$ in agreement with astrophysical measurements are obtained. Another choice of vacuum is more relevant to the early universe consisting of only radiation and vacuum energy, and we suggest it as a possible model of inflation.
16311021
Dressing symmetries
We study the group of dressing transformations in soliton theories. We show that it is generated by the monodromy matrix. This provides a new proof of their Lie-Poisson property. We treat in detail the examples of the Toda field theories and the Heisenberg model. We show that the group of dressing transformations is the classical precursor of the various manifestations of quantum groups in these models, e.g. algebraic Bethe ansatz, non-local currents, or quantum group symmetries. Finally, we define field multiplets supporting a linear representation of the dressing group and we show that their exchange algebras are encoded in the classical double.
7555598
SLE martingales and the Virasoro algebra
Abstract We present an explicit relation between representations of the Virasoro algebra and polynomial martingales in stochastic Loewner evolutions (SLE). We show that the Virasoro algebra is the spectrum generating algebra of SLE martingales. This is based on a new representation of the Virasoro algebra, inspired by the Borel–Weil construction, acting on functions depending on coordinates parametrizing conformal maps.
14748642
Differential equations for sine-Gordon correlation functions at the free fermion point
We demonstrate that for the sine-Gordon theory at the free fermion point, the 2-point correlation functions of the fields eiαΦ for 0 < α < 1 can be parameterized in terms of a solution to the sinh-Gordon equation. This result is derived by summing over intermediate multiparticle states and using the form factors to express this as a Fredholm determinant. The proof of the differential equations relies on a Z2 graded multiplication law satisfied by the integral operators of the Fredholm determinant. Using this methodology, we give a new proof of the differential equations which govern the spin and disorder field correlations in the Ising model.
119630140
Form factors, KdV and deformed hyperelliptic curves
Abstract We review and summarize recent works on the relation between form factors in integrable quantum field theory and deformation of geometrical data associated to hyper-elliptic curves. This relation, which is based on a deformation of the Riemann bilinear identity, in particular leads to the notion of null vectors in integrable field theory and to a new description of the KdV hierarchy.