14252776
Electroweak symmetry breaking and extra dimensions
Abstract Electroweak symmetry can be naturally broken by observed quark and gauge fields in various extra-dimensional configurations. No new fundamental fields are required below the quantum gravitational scale (∼ 10–100 TeV). We examine schemes in which the QCD gauge group alone, in compact extra dimensions, forms a composite Higgs doublet out of ( t , b ) L and a linear combination of the Kaluza–Klein modes of t R . The effective theory at low energies is the Standard Model. The top-quark mass is controlled by the number of active t R Kaluza–Klein modes below the string scale, and is in agreement with experiment.
122717656
Renormalization in indefinite metric theories
We consider the Lee model,V ⇆ N+θ, and a two neutral scalar meson model with indefinite metrics. It is shown that in general the coupling will cause positive definite bare states to become negative length dressed states through renormalization effects. This can render the theory unphysical depending upon the auxiliary conditions imposed with the indefinite metric.
15028896
Fractal theory space: Space-time of noninteger dimensionality
We construct matter field theories in ``theory space'' that are fractal, and invariant under geometrical renormalization group (RG) transformations. We treat in detail complex scalars, and discuss issues related to fermions, chirality, and Yang-Mills gauge fields. In the continuum limit these models describe physics in a noninteger spatial dimension which appears above a RG invariant ``compactification scale,'' M. The energy distribution of KK modes above M is controlled by an exponent in a scaling relation of the vacuum energy (Coleman-Weinberg potential), and corresponds to the dimensionality. For truncated-s-simplex lattices with coordination number s the spacetime dimensionality is 1+(3+2ln(s)/ln(s+2)). The computations in theory space involve subtleties, owing to the 1+3 kinetic terms, yet the resulting dimensionalites are equivalent to thermal spin systems. Physical implications are discussed.
10472717
Chiral multiplets of heavy-light mesons
The recent discovery of a narrow resonance in ${D}_{s}{\ensuremath{\pi}}^{0}$ by the BaBar Collaboration is consistent with the interpretation of a heavy ${J}^{P}{(0}^{+}{,1}^{+})$ spin multiplet. This system is the parity partner of the ground state ${(0}^{\ensuremath{-}}{,1}^{\ensuremath{-}})$ multiplet, which we argue is required in the implementation of ${\mathrm{SU}(3)}_{L}\ifmmode\times\else\texttimes\fi{}{\mathrm{SU}(3)}_{R}$ chiral symmetry in heavy-light meson systems. The ${(0}^{+}{,1}^{+})\ensuremath{\rightarrow}{(0}^{\ensuremath{-}}{,1}^{\ensuremath{-}})+\ensuremath{\pi}$ transition couplings satisfy a Goldberger-Treiman relation, ${g}_{\ensuremath{\pi}}=\ensuremath{\Delta}{M/f}_{\ensuremath{\pi}},$ where $\ensuremath{\Delta}M$ is the mass gap. The BaBar resonance fits the ${0}^{+}$ state, with a kinematically blocked principal decay mode to $D+K.$ The allowed ${D}_{s}+\ensuremath{\pi},$ ${D}_{s}+2\ensuremath{\pi},$ and electromagnetic transitions are computed from the full chiral theory and found to be suppressed, consistent with the narrowness of the state. This state establishes the chiral mass difference for all such heavy-quark chiral multiplets, and precise predictions exist for the analogous ${B}_{s}$ and strange doubly heavy baryon states.
119473346
Renormalization group fixed points and the Higgs boson spectrum
Abstract We study numerically the renormalization group equations for the Higgs potential of the two-doublet model assuming perturbative unification and sufficiently large initial quartic and Higgs-Yukawa couplings such that the full nonlinearities interplay. We obtain predictions for the physical Higgs boson spectrum in the two-doublet model up to systematic differences in fermion coupling schemes. Unambiguous predictions emerge only when there exists a heavy generation in which quarks couple to both doublets. In other cases we find that the potential can become quartically unstable at low energies for arbitrary initial stable values of the coupling constants.
11755173
Cosmology with ultralight pseudo Nambu-Goldstone bosons.
We explore the cosmological implications of an ultralight pseudo Nambu-Goldstone boson. With global spontaneous symmetry breaking scale $f\ensuremath{\simeq}{10}^{18}\mathrm{GeV}$ and explicit breaking scale comparable to Mikheyev-Smirnov-Wolfenstein neutrino masses, $M\ensuremath{\sim}{10}^{\ensuremath{-}3}\mathrm{eV}$, such a field, which acquires a mass ${m}_{\ensuremath{\varphi}}\ensuremath{\sim}{M}^{2}/f\ensuremath{\sim}{H}_{0}$, would currently dominate the energy density of the Universe. The field acts as an effective cosmological constant before relaxing into a condensate of nonrelativistic bosons. Such a model can reconcile dynamical estimates of the density parameter, ${\ensuremath{\Omega}}_{m}\ensuremath{\sim}0.2$, with a spatially flat universe, yielding ${H}_{0}{t}_{0}\ensuremath{\simeq}1$ consistent with limits from gravitational lens statistics.
125438498
Top quark mass measurements
The top quark, with its extraordinarily large mass (nearly that of a gold atom), plays a significant role in the phenomenology of EWSB in the Standard Model. In particular, the top quark mass when combined with the W mass constrains the mass of the as yet unobserved Higgs boson. Thus, a precise determination of the mass of the top quark is a principal goal of the CDF and D0 experiments. With the data collected thus far in Runs 1 and 2 of the Tevatron, CDF and D0 have measured the top quark mass in both the lepton+jets and dilepton decay channels using a variety of complementary experimental techniques. The author presents an overview of the most recent of the measurements.
54890488
Study of beam parameters of the CERN proton linac using a three dimensional bunch shape monitor
A Three Dimensional Bunch Shape Monitor (3D-BSM) has been developed for the CERN Proton Linac 2. A new area for beam studies at high intensities has been opened by this detector. Bunch density distributions in all three dimensions and their variations along the beam pulse can be obtained. Changing field gradients in linac quadrupoles, emittance variation along the bunch has been calculated. Measurements of beam halos become possible thanks to the large dynamic range of the device. Beam parameters at various linac settings have been measured and analysed. Introduction The new detector [1] allows the measurement of the three dimensional density distribution I(x,y,z) of a bunch and its evolution along the beam pulse. For example, using this distribution the first and second moments and the beam profiles in each direction (x,y,z) have been obtained. The CERN Linac 2 is a high intensity accelerator consisting of an RFQ and three Alvarez tanks producing 140 mA of protons at 50 MeV [2]. As proven during the detector commissioning, the 100 μm tungsten wire can operate safely with pulse lengths up to 145 μs. The insertion of the target in the beam does not disturb injection into the downstream booster synchrotron. Therefore the 3D-BSM can be used as a nondestructive beam diagnostic tool during linac operation. Bunch Shape Measurements of the 50 MeV Beam In Fig.1 the evolution of the longitudinal profile along the beam pulse is presented. The analysis of the figure as well as of the evolution of other beam parameters along the bunch shows that beam-loading is well compensated in Linac 2. There is no variation either of the bunch centre or the bunch shape along the entire pulse length. It has been demonstrated that the bunch shape changes along the pulse if beam-loading is not sufficiently compensated. This can be seen in Fig. 2 where the RF field in tank 3 has been increased by 4% while keeping the maximum power to the tank constant. 0.0 22.9 45.8 68.8 91.7 0 10 20 30 40 50 60 70
22673060
Ions for LHC: Beam Physics and Engineering Challenges
The first phase of the heavy ion physics program at the LHC aims to provide lead-lead collisions at energies of 5.5 TeV per colliding nucleon pair and ion-ion luminosity of 1027cm-2s-1. The transformation of CERN’s ion injector complex (Linac3-LEIR-PS-SPS) presents a number of beam physics and engineering challenges, which are described in this paper. In the LHC itself, there are fundamental performance limitations due to various beam loss mechanisms. To study these without risk of damage there will be an initial period of operation with a reduced number of nominal intensity bunches. While reducing the work required to commission the LHC with ions in 2008, this will still enable early physics discoveries.
135301057
The electron cooling device developed for LEAR
92814731
Performance of the ECR ion source of CERN's heavy ion injector
In fall 1994 the new heavy ion injector at CERN was brought into operation successfully and a lead beam of 2.9 ×10 ions per pulse was accelerated in the SPS up to an energy of 157 GeV/u. The ion source, whi h was supplied by GANIL (France) was in operation almost continuously over a period of about one year and proved to be very reliable. It produces a current of more than 100 μA of Pb 27+ (after the first spectrometer) during the afterglow of the pulsed discharge. The current stays within 5% of the maximum value for a time of about 1 ms, which is more than required by the accelerators. Measurements of the charge state distribution, emittance and energy spread, which were made during this time window, are presented together with other operating data. Presented at the 12th International Workshop on ECR Ion Sources, April 25-27, 1995, RIKEN, Japan