Rochester comes to Dallas

Opening the International Conference on High Energy Physics in Dallas on 6 August, Conference Chairman and Superconducting Supercollider (SSC) Laboratory Director Roy Schwitters read an encouraging message from US President George Bush. (Photos John Bird, SSC Lab)

Every two years, the traditional Superconducting Supercollider (SSC) International Conference on High Laboratory. Energy Physics, organized for the The decision could not have International Union of Pure and turned out to be more timely. On 17 Applied Physics (IUPAP), provides a June, an unexpected vote in the US major world stage. There are House of Representatives had intervening meetings, but the two- threatened the future of the SSC. If year 'Rochester' cycle (named after that decision had been upheld by the the first Conference in the series, Senate, the project for an 87- held in Rochester in 1950) is well kilometre machine to collide 20 TeV matched to the natural growth and proton beams would have been in development of the subject. real trouble. However on 3 August This year's meeting, held in the Senate wisely decided to back Dallas, Texas, from 6-12 August the SSC, so the Dallas physics reflected how verifying the Standard conference opened on 6 August in a Model and producing precision party-like atmosphere. electroweak physics results, Conference Chairman and SSC particularly at CERN's LEP electron- Laboratory Director Roy Schwitters positron collider, has now become a began the meeting, held in the major research industry. It also Southern Methodist University marked the physics debut of the new campus in Dallas, by reading a letter HERA electron-proton collider at the from US President George Bush DESY Hamburg Laboratory. By the which assured the audience that his time of the next Rochester meeting, Administration is committed to in Glasgow, Scotland, in July 1994, ensuring funding for the SSC and HERA's new physics frontiers will be maintaining its high priority. Only a major physics.' few days earlier, and before the Energy, the major paymasters (or At any Rochester meeting, the Senate vote, President Bush had 'cheerleaders' as Happer preferred to forthcoming venue is traditionally visited the SSC Laboratory to call them) of US high energy physics. confirmed, and at the 1990 underline his support for the project. Looking forward to SSC news Rochester meeting in Singapore, the In his opening speech, Schwitters featuring at future Rochester decision had been to stage the 1992 went on to pay tribute to the meetings, Happer saw the SSC event in Moscow. Subsequent events international support and being transformed into a truly made this impossible, and the cohesiveness which had challenged international project, much more so meeting was rapidly rescheduled for the initial unfavourable vote from the than had originally been conceived. Dallas, Texas, hosted by the House of Representatives. This He illustrated the increasing support, with CERN prominent, had international collaboration in major been helpful in restoring the SSC scientific projects by the proposed project to its rightful place. ITER scheme for a next generation Keynote speaker at the opening Tokamak for thermonuclear fusion, ceremony was William Happer, supported by Japan, Europe, Russia Director of the Office of Energy and the US. 'Such efforts to Research of the US Department of internationalize scientific projects will increase as times goes by,' he said.

In his keynote address at the opening session of the Dallas meeting, William Happer, Director Standard Model of the Office of Energy Research at the US Department of Energy said 'efforts to internationalize scientific projects will increase For more than a decade, major as time goes by'. physics meetings have been

CERN Courier, October 1992 1 Precision electroweak physics, dominated by the contributions from the four experiments at CERN's LEP electron-positron collider, was In his summary talk, Steven Weinberg the bread and butter of the Dallas meeting. underlined how electroweak physics has This shows a Z decay recorded by the Opal reached a new level of precision before he detector. went on to look hard at theoretical trends.

data. Here the tau lepton sector has Standard Model festivals. With this ('top') quark is constrained by Stand­ emerged as a major physics arena in twin picture of the electroweak ard Model consistency to lie some­ its own right, providing Standard unification of electromagnetism and where between 130 and 170 GeV, Model parameters to complement the weak force coupled with the the mass of the Higgs particles, those coming from other lepton quantum chromodynamics theory of responsible for the symmetry sectors. Valuable input here comes inter-quark forces looking breaking at the heart of the from the new measurements of the impregnable, Dallas summary electroweak theory, still roams tau mass at Beijing (BES), Cornell speaker Steven Weinberg could relatively freely. However Weinberg (CLEO) and DESY (Argus). show a 'Standard Conference looked forward to dramatic Throwing all electroweak Summary' transparency. improvements in the near future, information into the melting pot, The standard status of the finding the top at the Fermilab consistency arguments point to a top Standard Model is that it is in good Tevatron, and then measuring the mass in the range 118-170 GeV. The shape experimentally, but the sixth mass of the W boson to high mass of the Higgs particle looks at ('top') quark still needs to be found, precision once LEP is upgraded to first glance like being around 300 the mechanism of CP violation has to attain its full collision energy around GeV, but really could be anywhere in be explained, quantum 200 GeV. the range 50-1000 GeV, lower chromodynamics has yet to be made Then, the emerging precision masses now having definitely been completely solvable, and the picture could make a very close excluded by LEP data. Finding symmetry-breaking ('Higgs') check on the Standard Model, said where the top quark sits, either from mechanism which provides particles Weinberg, following the current experiments at Fermilab's Tevatron with mass must be uncovered. approach of 'oblique' radiative or further down the line, will provide a Electroweak physics now attains correction analyses (October 1991, surer indication of where the Higgs an impressive level of precision, page 2). should be found. largely due to the great success of Earlier, Luigi Rolandi of CERN LEP dominates the electroweak the experiments at LEP, said (who is also the current coordinator sector. Most results so far come from Weinberg. Electroweak physics for the LEP experiments) had the two million Zs seen by the four precision is now rivalling what once summarized the status of experiments - Aleph, Delphi, L3 and used to characterize quantum electroweak physics, where a major Opal - from 1989 to 1991. Rolandi electrodynamics. fraction of the world high energy hinted that this year's run was going While the long-expected sixth physics effort provides a wealth of well, promising a bumper harvest of

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30a Circle advertisement number on reader service form Persis Drell of Cornell - defining and testing Siegfried Bethke of Heidelberg - tests of the Standard Model quantum chromodynamics

Cornell's CESR ring, and Argus at DESY, as well as the E653 fixed target study at Fermilab all contributing. Unlike the comparable situation in the charm sector, where different mesons have different lifetimes, the B mesons (neutral, charged and containing a strange quark) appear to have fairly similar lifetimes. The recent appearance on

the scene of Bs mesons, containing a strange quark, adds a new richness to this physics. Another precision business is fixing quantitatively how the various quarks are related in weak decays, measuring the elements of the (Kobayashi-Maskawa) quark mixing matrix. A meson consisting of a heavy quark bound to a light antiquark can be looked on as a sort of hydrogen atom, and all sorts of Zs. In addition, valuable additional hyperfine corrections applied to came from Siegfried Bethke of precision has come this year by extract precision quark information. Heidelberg, speaking on tests of better fixes on the LEP beam energy Hydrogen atom approaches to heavy quantum chromodynamics. A wel­ using the resonance depolarization quarks systems were also covered come arrival in this sector is fresh method (November 1991, page 12), by Nathan Isgur of CEBAF in his talk data on the quark structure of nuclé­ where remaining uncertaincies of a on hadronic spectroscopy and ons (structure functions) coming from few MeV (in about 100 GeV) come structure, where heavy quark the New Muon Collaboration (NMC) from tidal effects! information provides valuable experiment at CERN. This helps to Stanford's SLC linear collider has 'engineering' input for the quark reconcile differences between previ­ long been in the shadow of LEP, but mixing matrix. ous measurements, although it a new feature this year is the emer­ LEP experiments now see comes too late for inclusion in some gence of valuable data using polar­ substantial particle mixing in the cases. ized beams (July, page 1). With neutral B meson system, an The analysis of hadron jet data some 5,000 events analysed, important step towards one day from LEP has become a skilled trade, asymmetry data presented at Dallas being able to look at CP violation in with the introduction of new could not yet rival LEP precision in this sector and complement the algorithms. Valuable new jet data this particular sector, but this should information learned so far from also comes from the E665 fixed soon be rectified, with a similar neutral kaons. target experiment at the Fermilab number still in the SLC data analysis In tau physics, concern has muon beam, which sees clear pipeline. persisted for seven years about an signals. The strong interaction Earlier, Persis Drell of Cornell had apparent deficit of certain decays, coupling (alpha-s) has now been summarized the situation in weak where the sum of all the possibilities measured in a wide range of decays, another physics area now did not add up to 100%. Taking a experiments, together covering a benefiting from a lot of precision hard look at the latest data, Drell did wide kinematic range and showing data. Much effort has gone into not advocate taking this deficit too how it varies with energy, becoming measuring the various B mesons seriously. very small as quarks effectively get (containing the fifth 'beauty' quark), Another presentation reflecting closer together, a condition known in with experiments at LEP, CLEO at the new wave precision physics the trade as asymptotic freedom.

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30b Circle advertisement number on reader service form Luigi Rolandi, as the current experimental coordinator at LEP, was well fitted to talk at Bjorn Wiik of DESY covered first results Dallas on precision tests of the electroweak from the new HERA electron-proton interaction. collider.

in the analysis of high energy proton- antiproton collisions.

Astrophysics and cosmology

There are two Standard Models in modern physics - the combined electroweak and QCD picture used by the particle physicists, and Big Bang cosmology. Astrophysics and cosmology sessions were once curiosities on the periphery of the programme at high energy physics conferences, but with these two Standard Models reaching out for Neutrinos each other, there is increasing The dawn of the HERA era contact between scientists studying Neutrinos are always controversial. the micro- and macrocosmos. Even in the short time since the At Dallas, Bjorn Wiik proudly gave an At Dallas, Lawrence Krauss of Neutrino 92 meeting in Grenada, update on HERA, now producing its Yale summarized new developments Spain, in June (September, page 1) first electron-proton collision physics in astrophysics and cosmology. Here, new results had emerged. at DESY. On the machine side, this the scene is dominated by the This year sees the first data from material had been covered at the implications of the COBE satellite gallium-based detectors sensitive to Hamburg Accelerator Conference results on the tiny fluctuations in the the neutrinos from proton-proton (see page 9). After Wiik's talk, CERN cosmic microwave background fusion reaction which supplies the Director General* Carlo Rubbia radiation announced earlier this year vast majority of the Sun's energy. At initiated applause for DESY's 'nice (June, page 1), and described in a Grenada, the Gallex international achievement'. Dallas parallel session by COBE team using a gallium detector in the Earlier, a historic parallel session senior investigator George Smoot of Italian underground Gran Sasso included the first physics talks from Berkeley. Laboratory had announced the first the two HERA experiments (B. Lohr Krauss explained how the COBE signals of proton-proton fusion for Zeus and F. Eisele for H1). Both fluctuations, of the order of one part neutrinos. However the SAGE speakers showed how their detectors in a hundred thousand, give new detector, operated by a US/Russian were producing very clean electron- insights into quantum gravity, into the team in Russia, had declined to proton collision data and probing inflation mechanism which is thought announce any results in June. At some kinematic regions far removed to have dominated the early Dallas, SAGE reported a figure from anything seen previously. In Universe, and 'dark matter' - invisible around 58 solar neutrino units (SNU), particular, they can already track how material which has to be there to less than the result around 83 SNU photoproduction rates behave in a account for the observed motion of reported by Gallex earlier. new energy range, so that some bold galaxies. With conventional solar neutrino theories can be scrapped. While the COBE fluctuations have calculations by John Bahcall With such clean physics been greeted as indicators of the predicting a total signal of 132 SNU, information so soon, and with HERA initial quantum 'seeding' which gave neutrino summarizer Hamish still having a lot more luminosity up birth to the Universe as we now know Robertson of Los Alamos preferred its sleeve, the future looks bright. it, gravitational waves could also be to take the average of the SAGE and This data will be invaluable for future playing a role. Smoot and his team Gallex results to get an observed SSC/LHC studies in the same way are now processing the second year signal which is 56% of the predicted that structure functions from fixed of COBE data, and the updated figure. This discrepancy - the famous target studies found ready application results are eagerly awaited. 'solar neutrino problem' - invites

6 CERN Courier, October 1992 Michael Peskin of SLAC - looking beyond the Standard Model explanation in terms of Micheyev/ summarized for everyone's benefit by Smirnov/Wolfenstein (MSW) H. Leutwyler of Bern (Non- resonant mixing, an effect which has perturbative approaches), L. Alvarez- been described as 'so beautiful that Gaume of CERN (Field Theory and Nature would be crazy not to use it'. String Theory) and R. Petronzio of However the gallium results, Rome (Lattice calculations). based on small event samples, are Ongoing experimental work in still potentially unstable and the heavy quark production was covered reported signals could yet change. by Joel Butler of Fermilab, while Results reported by SAGE have Jurgen Schukraft of CERN dealt with been mobile. heavy ion interactions, a field where * A traditional feature in the useful progress is being made en neutrino sector is usually improved route to higher energies and heavier mass limits. This year the electron ions. neutrino has been confined below about 10 electronvolts, and the tau neutrino below 31, rather than 35 The future crystal ball will become even clearer, MeV, with an improved result from and the upgraded machine could the Argus experiment at DESY. As the end of the Dallas meeting intercept some prime physics goals. However the muon neutrino has neared, the emphasis turned to To maintain CERN's position taken a step back from a previous future projects. Takahiko Kondo from requires a machine initially limit of 270 keV out to 500 keV. the Japanese KEK Laboratory looked complementary to LEP and HERA Although still on the agenda, a at detector development on a variety before finally taking over as the possible17 keV neutrino continued to of timescales, from completed physics spearhead, and this is the be shaky. technologies now entering use, such role of LHC - the 7.7 TeV per beam The Dallas meeting began, as silicon microvertex detectors and proton collider to be built in the LEP following the'Rochester tradition, with ring-imaging Cherenkovs, to the tunnel. A string of full scale a packed programme of parallel intense development work now superconducting magnets will be sessions, sometimes with up to six underway for experiments at the next tested next year, while other streams. With precision data and fine generation of hadron colliders, where preparations for LHC give promising details now becoming the physics detector dimensions are set to enter results. Its injection system - CERN's norm, it is in these sessions where a new ballpark and new technologies existing chain of proton accelerators - much of the work is done. In these will play an important role. On the has been tested in LHC-like parallel streams, the mass of data machine side, Robert Siemann of conditions. Cryogenic plant is from the four big LEP experiments SLAC summarized future accelerator appearing as part of the LEP 200 was very evident in sessions on technologies. programme. Rubbia also pointed out weak decays, B particle mixing, CERN Director General Carlo the attraction that LHC experiments heavy quark production, searches for Rubbia looked to the future of Europe have for physicists outside CERN new particles, and electroweak in general and CERN in particular. Member States. parameters. Europe, with LEP at CERN pumping For the SSC, being built just a few A detail emerging in the parallel out prime data, with HERA at DESY miles away from Dallas, Roy sessions was news that the double now coming on, and with major Schwitters emphasized the vertex events previously reported experiments at the unique Italian international aspect of the project. from neutrino interactions by the Gran Sasso underground Laboratory For example Beijing is helping with CCFR collaboration at Fermilab beginning to be productive, is in a the final stages of the injection linac (September, page 4) have not strong position. and Novosibirsk is assisting with the survived ongoing analysis. 'LEP is our crystal ball', declared challenging task of the Low Energy For theorists, there was ample Rubbia. With preparations at LEP Booster. material to digest, and current theo­ now pushing ahead for its full colli­ The link between the linac and retical developments were usefully sion energy of nearly 200 GeV, the this booster was a critical SSC

CERN Courier, October 1992 7 High strength fasteners for Nuclear Research

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8 CERN Courier, October 1992 Hamburg Accelerator Conference

bottleneck, said Schwitters. Increas­ From 20-24 July, Hamburg Tadao Fujii, representing the ing the transfer energy could pay welcomed the Fifteenth International International Union of Pure and handsome dividends in the bright­ Conference on High Energy Applied Physics, was quick to ness of the final beams. Meanwhile Accelerators (HEACC). Although congratulate the HERA team on its the first batch of 50mm diameter close on the heels of the European achievement - sentiments shared by dipole magnets was delivering Particle Accelerator Conference, held all present, for HERA, the most promising results (see page 21). in Berlin at the end of March (June, recent and original addition to the Trying to peer over the impenetra­ page 5), the Hamburg meeting world of large colliders was clearly ble Standard Model wall and look emphasised the world rather than star of the Hamburg show. beyond, Michael Peskin of SLAC saw European view, avoiding the danger Since the previous HEACC, held the Higgs mechanism as a of repetition. A natural highlight was three years ago in Japan, it appears parametrization, not an explanation. the recent commissioning success of that everyone, given the money, Despite the impenetrability of the the HERA electron-proton collider at knows how to build a synchrotron. wall, there could still be a map on the Hamburg's DESY Laboratory and its Now specialists either flock around far side, with possibilities for strong first high energy electron-proton the ultimate challenge of luminosity in and weak interaction routes. Com­ collision data. This gave the meeting the electron-ring factories or join the paring today's Standard Model with the feel of a family event celebrating mushrooming R&D in the even more Columbus' picture of the world in a newborn. intriguing prospect of colliding two 1492, Peskin looked forward to a In his opening remarks, linac beams head-on. Another voyage of discovery encountering an Conference Chairman Gus Voss of HEACC innovation noted by Gus unexpected New World of physics. DESY related that six years ago, Voss in his opening address was the With Texas-style organization, the when DESY had offered to host the large participation from the 1400 participants at the Dallas Conference, they had taken the risk Commonwealth of Independent meeting sometimes looked like a dot that HERA might not be ready in States - over 60 participants in all. on the vast landscape. As well as time. He had been reminded of the CERN Theory Division Leader having a chance to see SSC risk many times during HERA John Ellis led 'morning prayer', as he preparations at first hand, construction but was happy to be put it, with a review of today's participants also profited from a able to report that the first collisions Standard Model physics and a look specially arranged musical evening had already been observed and at beyond. An outstanding physics at Dallas' superb Myerson full energy (July, page 2). objective is to find the sixth ('top') Auditorium, featuring Pinchas Zuckerman. Here was an object lesson how, after almost two hundred years, a Standard Model (of Mozart chamber music) is no obstacle to genius and technical mastery.

By Gordon Fraser

The HERA electron-proton collider, now operating at DESY, Hamburg, was naturally the star of the International Conference on High Energy Accelerators, held in Hamburg from 20-24 July. Here conference participants get a close look at the new machine.

CERN Courier, October 1992 9