558 research outputs found
Gauge invariance and non-constant gauge couplings
It is shown that space-time dependent gauge couplings do not completely break
gauge invariance. We demonstrate this in various gauge theories.Comment: 18 page
Luminosity goals for a 100-TeV pp collider
We consider diverse examples of science goals that provide a framework to
assess luminosity goals for a future 100-TeV proton-proton collider.Comment: 11 pages, 9 figures. Discussion white paper, arising from the
programme on "The future of high energy physics", January 5-30, 2015, Jockey
Club Institute for Advanced Study of the Hong Kong University of Science and
Technology
Universal Spacing for Heavy Quarkonium Dissociation
When a heavy quark and the corresponding antiquark are separated by more than
fm, it becomes energetically favorable for a light quark-antiquark
pair to be produced, leading to fragmentation into a pair of flavored mesons.
The relation of this critical quark separation to other dimensional constants
of the strong interactions (such as the pion decay constant, the QCD scale, and
the light-quark constituent mass) is discussed.Comment: 7 pages, latex, 1 figure. Version to be published in Phys. Lett.
Gedanken Worlds without Higgs: QCD-Induced Electroweak Symmetry Breaking
To illuminate how electroweak symmetry breaking shapes the physical world, we
investigate toy models in which no Higgs fields or other constructs are
introduced to induce spontaneous symmetry breaking. Two models incorporate the
standard SU(3)_c x SU(2)_L x U(1)_Y gauge symmetry and fermion content similar
to that of the standard model. The first class--like the standard electroweak
theory--contains no bare mass terms, so the spontaneous breaking of chiral
symmetry within quantum chromodynamics is the only source of electroweak
symmetry breaking. The second class adds bare fermion masses sufficiently small
that QCD remains the dominant source of electroweak symmetry breaking and the
model can serve as a well-behaved low-energy effective field theory to energies
somewhat above the hadronic scale. A third class of models is based on the
left-right--symmetric SU(3)_c x SU(2)_L x SU(2)_R x U(1)_{B-L} gauge group. In
a fourth class of models, built on SU(4)_{PS} x SU(2)_L x SU(2)_R gauge
symmetry, lepton number is treated as a fourth color. Many interesting
characteristics of the models stem from the fact that the effective strength of
the weak interactions is much closer to that of the residual strong
interactions than in the real world. The Higgs-free models not only provide
informative contrasts to the real world, but also lead us to consider
intriguing issues in the application of field theory to the real world.Comment: 20 pages, no figures, uses RevTeX; typos correcte
Spacings of Quarkonium Levels with the Same Principal Quantum Number
The spacings between bound-state levels of the Schr\"odinger equation with
the same principal quantum number but orbital angular momenta
differing by unity are found to be nearly equal for a wide range of power
potentials , with . Semiclassical approximations are in accord with this behavior. The
result is applied to estimates of masses for quarkonium levels which have not
yet been observed, including the 2P states and the 1D
states.Comment: 20 pages, latex, 3 uuencoded figures submitted separately (process
using psfig.sty
Unanswered Questions in the Electroweak Theory
This article is devoted to the status of the electroweak theory on the eve of
experimentation at CERN's Large Hadron Collider. A compact summary of the logic
and structure of the electroweak theory precedes an examination of what
experimental tests have established so far. The outstanding unconfirmed
prediction of the electroweak theory is the existence of the Higgs boson, a
weakly interacting spin-zero particle that is the agent of electroweak symmetry
breaking, the giver of mass to the weak gauge bosons, the quarks, and the
leptons. General arguments imply that the Higgs boson or other new physics is
required on the TeV energy scale. Indirect constraints from global analyses of
electroweak measurements suggest that the mass of the standard-model Higgs
boson is less than 200 GeV. Once its mass is assumed, the properties of the
Higgs boson follow from the electroweak theory, and these inform the search for
the Higgs boson. Alternative mechanisms for electroweak symmetry breaking are
reviewed, and the importance of electroweak symmetry breaking is illuminated by
considering a world without a specific mechanism to hide the electroweak
symmetry.
For all its triumphs, the electroweak theory has many shortcomings. . . .Comment: 31 pages, 20 figures; prepared for Annual Review of Nuclear and
Particle Science (minor changes
Testing of Noodle Creek Site 41JS102 Jones County, Texas
Staff Archeologists from the Environmental Affairs Division of Texas Department of Transportation discovered buried cultural resources that constitute archeological site 41JS102, in June and July 2001 at the proposed location of a bridge replacement over Noodle Creek in Jones County, Texas. Shovel testing and backhoe trenching revealed cultural material at 65 cm below the surface. Following this discovery the Texas Department of Transportation made recommendations to the Texas Historical Commission to assess site 41JS 102 and they concurred. In September 2001 archeologists from the Texas Department of Transportation initiated the site assessment phase. Landowner complications halted that work before completion. Subsequently, TRC Environmental was provided a Work Authorization under an existing general services contract to complete the assessment of 41JS102 in December 2001. The fieldwork consisted of the hand excavation and documentation of eight 1 by 1 m test units and the digging and documenting of six backhoe trenches. Limited and scattered historic artifacts were recovered from the upper parts of the two alluvial terraces (T0 and T1). A prehistoric component with quantities of lithic debitage and sparse burned rocks, limited stone tools and mussel shells, and one possible cultural feature were encountered in a sloping, but well defined 10 to 15 cm thick zone in the T1 deposits. The Principal Investigator recommended prehistoric site 4 1JS102 was eligible for inclusion in the National Register of Historic Places and as a State Archeological Landmark. However, the staff at Texas Department of Transportation disagreed with that recommendation and presented an opposing case to the Texas Historical Commission who concurred with the Texas Department of Transportation\u27s recommendations. Consequently, no further archeological investigations will occur prior to the proposed development
Space-Time Evolution of the Oscillator, Rapidly moving in a random media
We study the quantum-mechanical evolution of the nonrelativistic oscillator,
rapidly moving in the media with the random vector fields. We calculate the
evolution of the level probability distribution as a function of time, and
obtain rapid level diffusion over the energy levels. Our results imply a new
mechanism of charmonium dissociation in QCD media.Comment: 32 pages, 13 figure
Meson Mass Splittings in the Nonrelativistic Model
Mass splittings between isodoublet meson pairs and between and
mesons of the same valence quark content are computed in a detailed
nonrelativistic model. The field theoretic expressions for such splittings are
shown to reduce to kinematic and Breit-Fermi terms in the nonrelativistic
limit. Algebraic results thus obtained are applied to the specific case of the
linear-plus-Coulomb potential, with resultant numbers compared to experiment.Comment: 29 pages with 2 tables and 4 figures, LBL-32872 and UCB-PTH-92/3
A novel approach to light-front perturbation theory
We suggest a possible algorithm to calculate one-loop n-point functions
within a variant of light-front perturbation theory. The key ingredients are
the covariant Passarino-Veltman scheme and a surprising integration formula
that localises Feynman integrals at vanishing longitudinal momentum. The
resulting expressions are generalisations of Weinberg's infinite-momentum
results and are manifestly Lorentz invariant. For n = 2 and 3 we explicitly
show how to relate those to light-front integrals with standard energy
denominators. All expressions are rendered finite by means of transverse
dimensional regularisation.Comment: 10 pages, 5 figure
- …