de Moriond , March 1st-8th, 2008
About this presentation
The present document does
not aim at providing a detailed specialist account of the latest
in particle physics presented and discussed in depth at the Rencontres
Our purpose is rather here to
present in rather general terms some key points of the
dealing both with the scientific content and with the specific format
makes the Rencontres de Moriond a unique venue.
Considerable work relating to the preparation and analysis of future
experiments was also presented,
even though space lacks to review it here.
We will thus refer the
particle physicist directly to the summary talks by Ken Peach
(exp), Marcela Carena (th) and the detailed scanned
slides (or later to the proceedings)
the details of each presentation can be examined freely.
The illustrations below are extracted from those summary talks, where
the reference to the respective presentations can be found.
We also welcome enquiries from
information professionals: beyond the ground material found below, we
them to contact the members of the program committee (the simplest is
proceed via the Moriond secretariat, see at end of this file).
In the following paragraphs,
" information is printed in italics.
While the LHC will constitute the ideal tool for the production
and detection of the (Brout Englert Higgs) scalar boson, (the missing
piece in the Standard Model), experiments at Tevatron are accumulting
data (although at lower energy and luminosity), and refining
considerably their analysis.
Searches and preparation for the Brout-Englert Higgs particle /
For the first time, their sensitivity this year extends to the level
expected in the Standard Model (although only for relatively heavy
scalars). (remember that, at the difference of its couplings, the
scalar boson is not predicted by the Standard Model, although
constraints from radiative corrections and indirect experimental data
favour rather light scalars).
Theoretical models are evolving in expectation for the LHC !
In the domain of the Scalar sector, and its variants, attention has
long concentrated on the Supersymmetric approach (which foresees a
doubling of the scalar
structure, and generally a rather light scalar (<130 GeV), except in
the NMMS extension. Many alternate models are however currently
proposed, notably based on extra dimensions (invoking or
not a duality between strongly and weakly coupled sectors à la
AdS/CFT). In particular, in warped models (Randall-Sundrum), the
fermions and scalars can be placed according to various scenarions on
the boundaries or in the bulk. An obvious prediction is particular
flavour effects for the Top quark family.
Other possibilities (in the line discussed last year by J
Vander Bij) involve mixing the canonical scalar with other states,
in an "unparticle" configuration (in practice, a continuous effective
mass distribution, rather than a single peak ), much harder to spot at
Link with Dark Matter
Even very simple models in the scalar sectors can introduce dark matter
(it is sufficient to have a conserved "parity", like Z2, similar
in a way to the much more evolved R parity in SuperSymmetry) ) . An
interesting possibility is that precisely this sector triggers the
Single top production , and Top
Precision increases in both
the Top mass and its properties.
Both FNAL experiments now see the single top production (thus by weak
interactions), and start to study its properties in some detail, This
is also an opportunity to serach for abnormal couplings of the Top
Bottom and Charm physics ,
Abundant data emerge from B factories (and Tevatron), not only on
the general oscillation/mixing parameters but also on
particular decay modes. The results are too numerous to review
here, and we send the reader to the aforementioned summary talks, or
the original presentations.
Glitches in the picture ?
An intriguiing result is the measurement of time-dependant CP
violation in the Kshort Pi Pi mode for B decays. While the Standard
Model expects results similar to the usual J/Psi Kshort,
the newest data (still quite preliminary) stand at 2 sigma from that
The summary talk also mentioned some discrepancies in the Bs decay
phases recently claimed by the UTfit team.(but too late for
presentation at this meeting)
The potential for detecting "beyond standard model", particularly in
radiative decays of B into s , is also the subject of methodical and
extensive theoretical investigation
The D° mixing has now been confirmed, and progress on CKM fits
From Charm physics to
Charm physics continues to be studied in depth. We will
not review the details here, but stress an interesting development,
namely the study (at BES) of the "gluon -rich" domain of radiative
J/Psi decay ( the decay indeed can involve the intermediary
state: photon + 2 gluons ). This long-unraveled field starts to give
important results, whch will soon be ampliified with more sensitive
equipment, and are thus an area to watch in the future!
<>Amongst the most
neutrinos were first conjectured to account for escaping momentum and
in weak decays. Nowadays well established members of the standard model
of electroweak interactions, it is now established that they have mass,
and that the various flavours mix (as do the quarks, but with very
diffetrent characteristics). The mass differences are estimated by
"oscillations" , while the absolute masses (and their nature :
Dirac , i.e. lepton-number conserving or Majorana) are not
establised. Whether the presence of neutrino masses (which
implies either right handed neutrinos or extra scalar fields) is
a departure from the "Standard Model' is merely a matter of definition
history; except maybe for Majorana masses, the changes are minimal ,
and similar to those introduced when generalising the Standard Model to
include more quark families; in any cases, the "gauge structure" is
With the MiniBoone data now published, one might have hoped for the
situation to settle in terms of neutrino mixings.
Yet, those very result (which at face value exclude the oscillation
interpretation of the former LSND data) have suscited considerable
On the one hand, while the MiniBoone data don't find any excess in the
expected domain of energy (and thus disprove the interpretation of LSND
as naïve oscillations), they also include an unexpected excess at
very low energy (below their initially planned energy cut). Possible
explanations for this excess have been suggested, in particular, the
contribution of anomalies to neutrino X -> neutrino X photon
diffusion. (the photon being misindentified as an electron). Such
contritutions certainly exist, but their exact importance must be
studied; ore generally low-energy neutrino diffusion processes are
Theoretical efforts have also aimed at reconciling the LSND and
MiniBoone results, either by adding more sterile neutrinos (a difficult
approach), or by using the subtle differences between the experiments.
Indeed, LSND and MiniBoone strive for studiyng the same domain of L/E
(distance/energy), but with different L and E. If the oscillation can
be shown to depend on energy (as is the case when interaction with
matter, à la MSW intervenes), this can be a way to reconcile
things (the new name "chameleon" has been forged to apply to such
situation ). The cost however seems to introduce new interactions
involving more light particles.
Generic departures and Lepton mixing
An increasingly important theoretical approach deals with departures
from standard processes in leptonic interactions.
On the one hand, a systematic study evaluates the possible low-energy
effects of mixing neutrinos with heavier (unseen) partners.
More generally Lepton Flavour violation is seen as a possible signal of
physics beyond the Standard Model, including extra dimensions,
supersymmetry ? ...
asymmetry, dark matter, cosmological constant, high energy cosmic rays.
Neutrinos have also become an
"astronomical" tool, with large neutino telescopes entering
a new era. The larger IceCube is successfully developing Amanda at the
but its searches for point sources have this far given negative
results. Antares now pursues its developments and identifies neutrino
Their search also puts bounds on dark matter candidates, through their
possible annihilation (in the center of the Earth, Sun, or of the
Galaxy) into neutrinos .
Direct searches for dark matter
They complement the indirect searches (see above), and
the collider searches for long-lived particles.
See the review talks for a detailed review of the current situation.
An interesting development is the use of an "old" tool , namely small
bubble chambers in the search for dark matter (the COUPP experiment)
Cosmic Rays after Auger results
Cosmic rays , paticularly the very high energy
ones, could teach us a lot baout our Universe, but also about particle
physics and fundamental interactions in general.
One of the outstanding issues is the
so-called "GZK" cut-off: above some energy, the collisions of cosmic
rays (protons) with the cosmic background (relic photons) reduces
dramatically their effective range, resulting in an expected sharp
Another issue, particularly with very high energy cosmic rays, is their
physical origin (what are the cosmic accelerators involved), and, in an
associated way, their exact composition.
Answers to these questions are coming now,
and we are probably at a turning point in high energy cosmic rays
astronomy and astrophysice. (note that many of these questions
also arise for the neutrino telescopes, mentioned at the beginning of
Very high energy cosmic rays (and also very
high energy neutrinos) are a rare occurence, requiring the current
large instruments (from 1 to several squared kilometers) to achieve any
statistics. Even so, localizing sources remains an elusive task, since
the identification of a source by any given experiment would require
several events originiating from that direction, .. a sensitivity not
The AUGER experiment (even still only partially deployed) has made
impressive breakthroughs , and for this reason was the subject of
Meanwhile, alternate strategies are based on catalog searches. In simple
terms, this involves pooling together a number of potential sources (on
the basis of theoretical prejudice, for instance active galactic
nuclei), to associate a small area around each of the potential
sources, and to consider the total surface constituted from those
patches. If this area receives significantly more events than an
equivalent area not associated to the potential sources, a correlation
is established... This correlation establishes a link between the
observed cosmic rays and at least a subset of the considered catalog of
potential sources (or possibly other obtject closely associated).
As we will see below, it does not, at the present stage validate the
composition of the whole catalog.
First of all, the experiment has now confirmed the presence of the GZK
On a more technical level, considerable work (and progress) is devoted
to study the calibration of the "air showers' (the ratio of the light
detected to the energy deposited
in the high atmosphere by incoming cosmic rays), a complicated issue
which also requires a good knowledge of the atmosphere.
The most exciting result however was the established correlation
between high-energy cosmic rays and a catalog involving Active Galactic
This achievement is impressive.
But physicists are impatient people, and, this result barely obtained,
they want to go further... and are already venturing into the
following step, namely, the unraveling of the catalogs.
Indeed, establishing a correlation with a catalog in no way means that
all the potential sources involved indeed contribute. Acutally, even
the presence of a few (one?) powefull source in the catalog could
induce such a general correlation. The next steps will involve
detailing such catalogs, or reversing the procedure, and looking for
parts of the catalog contributing less than naïvely expected. We
look forward to exciting times in this, ... but of course the best
indication will come when experiments will localize individual sources
based on their data alone.
for the LHC ... and further Tevatron results
Several presentations dealt with the current searches
(supersymmetry, extra dimensions, Kaluza-Klein particles, ..) at the
Tevatron, but also with the final preparation for the LHC start-up. We
don't have the space to enter here in a detailed presentation, but this
augures in the best way for the next Moriond meeting!.
A special word about the Rencontres de Moriond
For 40 years now, the Rencontres
de Moriond, initiated by a small group of physicists around Professor
Thanh Van, have brought together scientists from around the world in a
unique conference format.
The size of the meeting is voluntarily
to ensure a maximum of personal contact, and to avoid parallel
all the presentations occur in plenary sessions, with strict
for experimenters to aim their talks at theorists and vice versa.
time is foreseen for general discussions between the talks, and special
extended discussions are set up by the organizers as the need arises .
More important however are the private
in particular between theorists and experimenters, where projects can
An extended break in a long working day, and the setting in a winter
resort do a lot to promote a relaxed and confident atmosphere, which
Another striking feature is the wide age range
of participants, but here, the senior staff tends to stay in the
and bring comments and suggestions while presentations are made by the
young scientists who conducted the detailed analysis. Often this is
first international meeting, (and for this European support plays
a crucial role) and the quality of their presentations is
The present review is by
essence a subjective presentation of the highlights of the
de Moriond Electroweak2007; remarks and criticisms are welcome :
Frère : email@example.com
detailed in formation on
year's "Rencontres de Moriond" and on future related events can be
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