ICHEP
06
Rochester conference goes back to Russia
Moscow hosted this year's
major summer conference, which presented the latest news across a
broad range of topics. Gennady Kozlov and Simon Eidelman report.
Résumé
La Conférence de Rochester de retour en Russie
La Conférence internationale sur la physique des hautes énergies
(ICHEP), connue aussi sous le nom de Conférence de Rochester, s'est
à nouveau tenue en Russie à la fin juillet, cette fois à Moscou, où
elle a rassemblé un millier de physiciens de 53 pays. Comme à
l'accoutumée, séances plénières et sessions parallèles se sont
combinées avec des présentations sur panneau. Les thèmes clés
allaient de l'astrophysique aux scénarios théoriques et recherches
expérimentales au-delà du modèle standard, en passant par la
cosmologie, la physique des ions lourds, les modes rares de
désintégration et la spectroscopie hadronique. Parmi les sujets
traités figuraient aussi la technologie des grilles, les nouveaux
accélérateurs et détecteurs de particules, et certains aspects de la
théorie des champs quantiques comme de la théorie des
cordes.
In summer 1976, the International Conference on High Energy
Physics (ICHEP), known traditionally as the Rochester conference,
was held in Tbilisi, the last time it would take place within the
USSR. Thirty years later, the Rochester conference returned to
Russia, when around a thousand physicists from 53 countries attended
ICHEP'06, held on 26 July – 2 August in the Russian Academy of
Sciences in Moscow. The extensive scientific programme contained the
customary mixture of plenary reports, parallel sessions and poster
presentations. For six days, participants discussed key issues in
high-energy physics, ranging from astrophysics and cosmology,
through the physics of heavy-ions, rare decays and hadron
spectroscopy, to theoretical scenarios and experimental searches
beyond the Standard Model. Topics also included Grid technology for
data processing, new accelerators and particle detectors, and
mathematical aspects of quantum field theory and string theory.
In his opening speech, the co-chair of the conference, Victor
Matveev, emphasized that the entire community of Russian high-energy
physicists was honoured to host the major international conference
of 2006. The participants were also greeted by the director of the
Budker Institute of Nuclear Physics (BINP) and co-chair of the
conference, Alexander Skrinsky, and deputy rector of the Lomonosov
Moscow State University, Vladimir Belokurov. The vice-chair of the
organizing committee, and director of the Joint Institute for
Nuclear Research (JINR), Alexei Sissakian then spoke about the
structure of ICHEP'06 and its scientific programme.
Duality, QCD and
heavy-ions
On the theory side, the progress in so-called "practical theory"
is evident, primarily in the sophisticated calculations in quantum
chromodynamics (QCD) presented by Giuseppe Marchesini of
Milano-Bicocca University and Zvi Bern of the University of
California, Los Angeles. Gerritt Schierholz from DESY, Adriano Di
Giacomo of Pisa University and Valentin Zakharov of the Institute
for Theoretical and Experimental Physics (ITEP), Moscow, explained
the remarkable achievement of the splendid harmony between
analytical calculations and the results obtained on the lattice
using dynamical quarks.
The theoretical discussions emphasized the concept and use of
gravity-gauge duality in a framework generalizing the anti-de Sitter
space/conformal field theory correspondence. This duality is a
conjectured relationship between confining gauge theories in four
dimensions on the one hand, and gravity and string theory in five
and more dimensions on the other. DESY's Volker Schomerus described
how, when applied to QCD, this approach reproduces numerous
non-perturbative features of strong interactions, from the
low-energy hadron spectrum through Regge trajectories and radial
excitations to quark counting rules. On the experimental side, Pavel
Pakhlov of ITEP Moscow, Antonio Vairo of Milano University and
Alexandre Zaitsev of the Institute for High Energy Physics (IHEP)
Protvino, reported on the numerous candidates for exotic hadronic
states, both with light quarks only and with heavy quarks and/or
gluons, that have been confirmed or newly reported by teams from the
VES experiment in Protvino, BES II in Beijing, E852 at Brookhaven,
CLEOc at Cornell, Belle at KEK, and BaBar at SLAC. These exotic
states have still to be interpreted theoretically, within either
gravity/gauge duality or more traditional approaches.
The Relativistic Heavy Ion Collider (RHIC) at the Brookhaven
National Laboratory is intensively studying a relatively new area of
QCD – the properties of matter at high temperatures and high
particle densities. Timothy Hallman from Brookhaven, Larisa Bravina
of the Skobeltsyn Institute of Nuclear Physics (SINP) Moscow
University, Nu Xu of Lawrence Berkeley National Laboratory (LBNL),
and Oleg Rogachevsky of JINR, among others, presented numerous
experimental results, some of which were reported for the first
time. These results suggest, quite surprisingly, as Xin-Nian Wang of
LBNL explained, that collisions of highly energetic ions at RHIC
result in the formation of strongly coupled quark–gluon matter,
rather than weakly interacting quark–gluon "gas". Here, too,
gravity/gauge duality can reflect the most remarkable properties
such as the low viscosity of quark–gluon "fluid", jet quenching and
so on.
Karel Safarik from CERN and Lyudmila Sarycheva of SINP described
how QCD will be probed at even higher temperatures at the Large
Hadron Collider (LHC) at CERN. Sissakian and Alexander Sorin of JINR
reported on plans at the JINR Nuclotron for complementary studies of
matter at lower temperatures but high baryon number densities; there
are also plans at GSI, Darmstadt. Most likely, matter at these
extreme conditions will exhibit new surprising properties in
addition to those observed at RHIC.
Quarks and leptons
With the B-factories and Tevatron operating, this conference
witnessed impressive progress in flavour physics, including B meson
decays, processes with CP violation, b → s and
b → d transitions and so on, which featured in the review
talks by KEK's Yasuhiro Okada and Masashi Hazumi and Robert
Kowalewski from Victoria University. The discovery of Bs
oscillations at the Tevatron was one of the highlights of the year.
Doug Glenzinski of Fermilab reported on these results from the CDF
collaboration, which reveal a mass difference between the mass
eigenstates equal to 17.31 ps-1 (central value)
(CERN Courier June 2006 p8). All data on flavour physics, including
CP violation and Bs oscillations, are now well described
by the Standard Model and Cabibbo–Kobayashi–Maskawa theory. Thus,
the Standard Model once again has passed a series of highly
non-trivial tests, this time in the heavy-quark sector.
Dugan O'Neil of Simon Fraser University and Florencia Canelli
from Fermilab were among those presenting precision measurements of
the masses of the heaviest known particles, which are still an
important aspect of experimental high-energy physics. New results
presented at the conference were based mainly on data from the CDF
and D0 collaborations at the Tevatron. The top quark became lighter
than it had been at the Beijing Conference in 2004 (CERN Courier
January/February 2005 p37): now its mass is 171.4±2.1 GeV.
Measurements of the W-boson mass are also more accurate. Making use
of these data, the Electroweak Working Group has produced a new fit
for the mass of the Standard Model Higgs boson,
mh = 85-28+39 GeV,
which is somewhat lower than before. According to this fit, the
upper limit on the Higgs boson mass is 166 GeV, as Darien Wood
of Northeastern University explained. Yuri Tikhonov from BINP
presented recent high-precision measurements of the mass of the τ
lepton at Belle and at the KEDR detector at BINP, which have
confirmed lepton universality in the Standard Model.
Beyond the Standard Model
The conference paid considerable attention to the search for new
physics. Numerous possible properties beyond the Standard Model are
even more strongly constrained than before, including supersymmetry;
extra space–time dimensions; effective contact interactions in the
quark and lepton sectors; additional heavy-gauge bosons; excited
states of quarks and leptons; and leptoquarks. This was emphasized
in various talks by Elisabetta Gallo of INFN Florence, Roger Barlow
of Manchester University, Herbert Greenlee of Fermilab, Stephane
Willocq of Massachusetts University and others. Yet most of the
community is confident that new physics is within the reach of the
LHC. Indeed, more theoretical scenarios for tera-electron-volt-scale
physics beyond the Standard Model were presented at the conference,
in talks for example by Rohini Godbole of the Indian Institute of
Science, Alexander Belyaev of Michigan University, Pierre Savard of
Toronto University and TRIUMF, Sergei Shmatov and Dmitri Kazakov of
JINR, and Satya Nandi of Oklahoma University. Notable exceptions
were Holger Bech Nielsen of the Niels Bohr Institute, who argued
that even the Higgs boson might never be discovered (for a not
necessarily scientific reason), and Mikhail Shaposhnikov of Lausanne
University and the Institute for Nuclear Research (INR) Moscow, who
defended his "nuMSM" model, which accounts for all existing data in
particle physics and cosmology at the expense of extreme
fine-tuning.
CERN's Fabiola Gianotti raised much interest by discussing the
tactics for early running at the LHC, reflecting the community's
thirst for new physics and the high expectations for the LHC. More
generally, there was a sense of expectation as this was the last
Rochester meeting before the start-up of the LHC.
The properties of neutrinos continue to be among the top issues
in high-energy physics. Geoff Pearce of the Rutherford Appleton
Laboratory presented the first data from a new player, the MINOS
collaboration, which support the pattern of the oscillations of muon
neutrinos observed by the Super-Kamiokande and KEK-to-Kamioka (K2K)
experiments. Other collaborations presented refined analyses of
their data in talks by Kiyoshi Nakamura of KamLAND and Tohoku
University, Yasuo Takeuchi of Super-Kamiokande and Tokyo
University, keVin Graham of the Sudbury Neutrino Observatory
and Carleton University, Valery Gorbachev of the Russian American
Gallium Experiment and INR Moscow, and Yuri Kudenko of K2K and INR.
These agree overall on oscillations of both electron and muon
neutrinos, with evidence for oscillations of muon neutrinos into tau
neutrinos confirmed by the Super-Kamiokande experiment. Also, the
KamLand experiment has confirmed and enhanced the case for
geo-neutrinos. The dominating oscillation parameters are now
measured with the precision of 10–20%, except for the smallest
mixing angle θ13 and a possible CP-violating phase, as
Regina Rameika of Fermilab, Ferruccio Feruglio of Padova University
and Kunio Inoue of Tohoku University explained. Interestingly, the
range of neutrino masses
0.01 eV < mν < 0.3 eV,
suggested by neutrino oscillation experiments, as well as by
cosmology and direct searches, is in the right ballpark for
leptogenesis – a mechanism for the generation of the
matter–antimatter asymmetry in the universe.
Astroparticle physics is another area of continuing interest.
Anatoli Serebrov of Petersburg Nuclear Physics Institute presented a
new measurement of the neutron lifetime, which makes a significant
contribution to the calculation of the abundance of primordial
helium-4 in the universe. Techniques for the direct and indirect
detection of dark-matter particles are rapidly developing, with
indications for positive signals from DAMA and EGRET still
persisting, as described by Alessandro Bettini of INFN Padova and by
Kazakov. In cosmic-ray physics, the Greisen–Zatsepin–Kuzmin cut-off
in the spectrum of ultra-high-energy cosmic rays is still an issue.
Giorgio Matthiae of Rome University "Tor Vergata" presented the
first data from the Pierre Auger Observatory. Masahiro Teshima of
the Max Planck Institute, Munich, and Gordon Thomson of Rutgers
University presented the new analyses by the AGASA and HiRes
collaborations, respectively. As a result, as Yoshiyuki Takahashi of
Alabama University explained, the discrepancy between different
experiments is now reduced.
Traditionally, the Rochester conferences discuss future
accelerators for high-energy physics and new developments in
particle detection, and receive reports from the International
Committee for Future Accelerators (ICFA) and the Commission on
Particles and Fields (C11) of the International Union of Pure and
Applied Physics (IUPAP). This was particularly timely in Moscow in
view of the upcoming start-up of the LHC. At present, the scientific
community is discussing a new megaproject – the large linear
electron–positron collider with an energy of 0.5–1.0 TeV, known
as the International Linear Collider (ILC). Together with the LHC,
the ILC will be a unique tool for studying fundamental properties of
matter and the universe. The talks by Skrinsky, DESY's Albrecht
Wagner and Rolf Heuer, and CERN's Lyn Evans discussed the prospects
for the project, including the contribution from Russia. Gregor
Herten of Freiburg University, who heads the IUPAP Commission (C11),
said that fundamental science is very important in Russia, and that
the research conducted by Russian scientists is highly esteemed
around the world.
Valery Rubakov of INR Moscow closed the conference with a summary
talk emphasizing both the current confusion of some theorists
regarding new physics and the impact of the LHC on the entire field
and beyond. The hope is that, with results from the LHC, at least
some of the numerous questions raised in Moscow will be answered at
the next Rochester conference, to be held in summer 2008 in
Philadelphia.
The ICHEP'06 conference was jointly organized by the Russian
Academy of Sciences, the Russian Federation (RF) Ministry of
Education and Science, the RF Federal Agency on Science and
Innovation, the RF Federal Agency on Atomic Energy, the Lomonosov
Moscow State University and JINR, the main coordinator of the
meeting. It was financially supported by IUPAP, the Russian
Foundation for Basic Research, RAS, JINR and the RF Federal Agency
on Science and Innovation.
• The authors are indebted to Valery Rubakov for his help in
preparing this article.
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