754 research outputs found
The Nobel Prize in Physics 1999
The last Nobel Prize of the Millenium in Physics has been awarded jointly to
Professor Gerardus 't Hooft of the University of Utrecht in Holland and his
thesis advisor Professor Emeritus Martinus J.G. Veltman of Holland. According
to the Academy's citation, the Nobel Prize has been awarded for 'elucidating
the quantum structure of electroweak interaction in Physics'. It further goes
on to say that they have placed particle physics theory on a firmer
mathematical foundation. In this short note, we will try to understand both
these aspects of the award. The work for which they have been awarded the Nobel
Prize was done in 1971. However, the precise predictions of properties of
particles that were made possible as a result of their work, were tested to a
very high degree of accuracy only in this last decade. This was done in a
series of measurements in the experiments in the accelerator laboratories at
CERN (Geneva) and Fermilab. To understand the full significance of this Nobel
Prize, we will have to summarise briefly the developement of our current
theoretical framework about the basic constituents of matter and the forces
which hold them together. In fact the path can be partially traced in a chain
of Nobel prizes starting from one in 1965 to S. Tomonaga, J. Schwinger and R.
Feynman, to the one to S.L. Glashow, A. Salam and S. Weinberg in 1979, and then
to C. Rubia and Simon van der Meer in 1984 ending with the current one.Comment: 5 pages, LateX, no inline figures. Six 'boxes' included separately as
six jpg files. These jpg files as well as 10 separate pdf files (one for each
printed page) can be accessed from
http://144.16.74.196/~www/resonance/npp99res.htm. added journal re
Predictions for Higgs and SUSY Higgs properties and their signatures at the Hadron Colliders
In this talk I present a discussion of the theoretical bounds on the mass of
the Higgs in the Standard Model (SM) as well as in the Minimal Supersymmetric
Standard Model (MSSM). Then I will point out a few facts about the couplings of
scalars that are relevant for its search at hadronic colliders. After that I
discuss the search possibilities at the Tevatron and the LHC, paying special
attention to the issue of how well one can establish the quantum numbers and
the couplings of the Higgs, when (if) it is discovered.Comment: 12 pages, 7 figures, Latex, requires mprocl.sty included, Invited
talk at the 'Hadron Collider Physics XIII', Jan.14-20, 1999, Bombay, India.
(To appear in the proceedings
Eikonalized mini-jet cross-sections in collisions
In this note we assess the validity and uncertainties in the predictions of
the eikonalised mini-jet model for . We are able
to find a choice of parameters where the predictions are compatible with the
current data. Even for this restricted range of parameters the predictions at
the high c.m. energies, which can be reached at the TeV energy
colliders, differ by about . LEP 2 data can help pinpoint these
parameters and hence reduce the uncertainties in the predictions.Comment: 5 pages, latex, requires epsfig.sty, a4wide.sty, full ps file
available at http://hpteor.lnf.infn.it/pancheri/lc2000.p
Strange freezeout
We argue that known systematics of hadron cross sections may cause different
particles to freeze out of the fireball produced in heavy-ion collisions at
different times. We find that a simple model with two freezeout points is a
better description of data than that with a single freezeout, while still
remaining predictive. The resulting fits seem to present constraints on the
late stage evolution of the fireball, including the tantalizing possibility
that the QCD chiral transition influences the yields at sqrt(S)=2700 GeV and
the QCD critical point those at sqrt(S)=17.3 GeV
Total Cross-sections
We examine the energy dependence of total cross-sections for photon processes
and discuss the QCD contribution to the rising behaviourComment: 5 pages, LaTeX, 2 figures, talk presented by G. Pancheri at Photon -
2001, The International Conference on Structure and Interactions of Photons,
Ascona, Sept. 2-7,2001. To appear in the proceeding
Invisible Decays of the Supersymmetric Higgs and Dark Matter
We discuss effects of the light sparticles on decays of the lightest Higgs in
a supersymmetric model with nonuniversal gaugino masses at the high scale,
focusing on the `invisible' decays into neutralinos. These can impact
significanlty the discovery possibilities of the lightest Higgs at the LHC. We
show that due to these decays, there exist regions of the space where
the B.R. becomes dangerously low even after imposing
the LEP constraints on the sparticle masses, implying a possible preclusion of
its discovery in the channel. We find that there exist regions
in the parameter space with acceptable relic density and where the ratio falls
below 0.6, implying loss of signal in the channel. These
regions correspond to masses which should be
accessible already at the Tevatron. Further we find that considerations of
relic density put lower limit on the U(1) gaugino mass parameter
independently of and .Comment: 17 pages, 11 figures, Talk presented at Appi2002, Accelerator and
Particle Physics Institute, Appi, Iwate, Japan, February 13--16 200
Photon-Photon total inelastic cross-section
We discuss predictions for the total inelastic gamma-gamma cross-section and
their model dependence on the input parameters. We compare results from a
simple extension of the Regge Pomeron exchange model as well as predictions
from the eikonalized mini-jet model with recent LEP data.Comment: 7 pages, LateX, 2 eps figures. Talk presented at Photon'97, Egmond
aan Zee, May 199
Moderately light charged Higgs in \cp MSSM and NMSSM
In this talk I discuss some aspects of the phenomenology of a moderately light charged Higgs () with a mass \gts 130 GeV, lighter than the top quark, at the LHC. A charged Higgs in this mass range is still allowed in next-to-minimal Supersymmetric Standard Model (NMSSM) at low as well as in CP-violating (\cp) Minimal Supersymmetric Standard Model (MSSM) for a certain choice of \cp parameters, still respecting all the LEP-II bounds. In both the cases, the has a large branching ratio in the channel, where denotes a generic Higgs which is dominantly pseudoscalar and hence may be substantially lighter than the LEP-II mass bound. This decays dominantly into a pair. Thus production of in the top decay gives a striking signal at the LHC, where one of the top quarks decays into the channel, via and . The characteristic correlation between the , and invariant mass peaks helps reduce the Standard Model (SM) background very effectively. For these low values of the channel does not provide any reach for the . Thus this is a signal for both a light charged and a light , which is mostly pseudoscalar in nature and decays dominantly into a pair
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