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Heads-up followup



Jack,
I got distracted yesterday afternoon and forgot to send it.
Sorry!

Geoff


Subject: the desy press release!

From: SMTP%"folkerts@desy.de" 18-FEB-1997 16:13:31.70
Subj: DESY / HERA: Embargo

Return-Path: <folkerts@x4u2.desy.de>
From: "Petra Folkerts" <folkerts@desy.de>
Organization: DESY

Deutsches Elektronen-Synchrotron DESY
Notkestrasse 85
D - 22607 Hamburg, Germany



Hamburg, February 18, 1997


DESY Information for some Science Journalists and Editors
__________________________________________________________________
EMBARGO until Wednesday, February 19, 1997, 11:00 a.m.
(Local Hamburg Time)
SPERRFRIST: Mittwoch, 19. Februar 1997, 11.00 Uhr
__________________________________________________________________

More events than expected from the Standard Model
- Deep inelastic electron-proton scattering measurements at the DESY
accelerator HERA in a previously unexplored kinematic region -

The two HERA experiments, H1 and ZEUS, observe an excess of events
above expectations at high-x ( or M = sqrt(xs) ), y, and Q-squared.
For Q-squared > 15,000 GeV-squared, the joint distribution has a
probability of less than one per-cent to come from Standard Model NC
DIS processes. Within this model, the predictions are known with
confidence. Similar probabilities occur for masses M larger than 175
GeV. The events at high Q-squared and large M are particularly
interesting because they occur in a previously unexplored region for
deep inelastic scattering. Increased luminosities from the forthcoming
data taking period, March-October, 1997, will clarify whether the
observed effect is a statistical fluctuation or a signal of new
physics.

HERA Hadron-Electron Ring Accelerator facility
DIS deep inelastic scattering
NC neutral current (exchange of a Z-boson or a
photon)
x Bjorken scaling variable (fraction of
the proton momentum
carried by the scattered parton)
s center-of-mass energy of the electron-proton
collision
Q-squared squared momentum transfer of the collision
y Q-squared / M-squared
M center-of-mass energy of the electron-parton
system
GeV Gigaelectronvolt


Both international teams, H1 and ZEUS, independently analysed their
data sample of high-energy deep inelastic scattering accumulated since
1994 at HERA. During these three years HERA ran with 27,5 GeV
positrons colliding head-on with 820 GeV protons. The observed events
have the typical signature of DIS reactions: the positron is scattered
off a parton inside the proton through a large angle; the struck
parton generates a high-energy hadron jet. Both groups compared their
measurements with Monte Carlo calculations based on the Standard Model
of NC DIS.

Both HERA collaborations, H1 and ZEUS, have presented their results in
a DESY Seminar on Wednesday, February 19, 1997. Both papers will be
submitted to ,Zeitschrift fuer Physik" on Monday, February 24, 1997.
The preprints can then be found on the World Wide Web.

The title of the H1 paper is ,Observation of Events at very High
Q-squared in ep Collisions at HERA". DESY Preprint No 97-024.
http://www-h1.desy.de/h1/www/publications/org_publ.html

The title of the ZEUS paper is: ,Comparison of ZEUS Data with Standard
Model Predictions for e+p -> e+X Scattering at High x and Q-squared".
DESY Preprint No 97-025.
http://www-zeus.desy.de/zeus_papers/zeus_papers.html

The H1 group has about 400 members from the following 12 countries:
Belgium, Czech Republic, France, Germany, Italy, Poland, Russia,
Slovak Republic, Sweden, Switzerland, United Kingdom, United States of
America. The ZEUS group has about 430 members from the following 12
countries: Canada, Germany, Israel, Italy, Japan, Korea, Netherlands,
Poland, Russia, Spain, United Kingdom, United States of America. Both
detectors were planned, financed, constructed and are operated by
these joint international collaborations.


The Deutsches Elektronen-Synchrotron DESY is the German research
center for basic research in particle physics and investigations with
synchrotron radiation. It is a publicly funded national research
center based in Hamburg, with a branch institute in Zeuthen near
Berlin. The annual budget amounts to 275 million German marks. The
Federal Government (Federal Ministry for Education, Science, Research
and Technology ( bmbf )) bears 90 per-cent of the budget and the City
of Hamburg or the federal state of Brandenburg the remaining 10
per-cent. DESY is a member of the Hermann von Helmholtz Association of
German Research Centers (HGF). 3000 scientists from 280 universities
and research institutes from 35 countries all over the world are
participating in the research at DESY, 1300 of them in particle
physics, 1700 in experiments with synchrotron radiation.

The Hadron-Electron Ring Accelerator facility HERA is the only
facility in the world in which electrons or positrons and protons
collide. At HERA physicists are able to observe electron/positron
proton collisions at center-of-mass energies which are an order of
magnitude above energies previously available. In this type of
collision structures inside the proton can be studied down to one part
in a thousand of the size of the proton itself.

Inside HERA the two particle beams circulate in opposite directions in
separate storage rings and are brought to head-on collision at two
interaction points. These are equipped with the detectors H1 and ZEUS,
which have both been taking data since the beginning of the HERA
research program in 1992. As well as these collision experiments HERA
accomodates two beam-target experiments: HERMES, in operation since
1995, uses the polarized electron beam to investigate the origin of
nucleon spin; HERA-B, scheduled to start in 1998, will use the proton
beam for the study of CP violation in the B-meson system.

The underground storage ring facility HERA has a circumference of
6,336 meters. It was constructed from 1984 to the end of 1990, when
the operation began. The first particle collisions were observed in
October 1991; the research program started in June 1992. Since then
the integrated HERA luminosity continuously increased from 0,05
inverse picobarn (1992), to 1 inv.pb (1993), to 6,2 inv.pb (1994), to
12,3 inv.pb (1995), to 17,2 inv.pb (1996). For the 1997 HERA run an
integrated luminosity of 25 inverse picobarn is expected.

HERA was constructed in an international collaboration: about fifteen
per-cent of the total costs of about 1110 million German marks came
from foreign countries. Institutions in Canada, China, Czechoslovakia,
France, Israel, Italy, Netherlands, Poland, United Kingdom, and USA
contributed through components and delegation of physicists,
engineers, and technicians to Hamburg during the construction of HERA.
***



For more detailed information:

DESY Telephone: (+4940) 8998-

Bjoern H. Wiik, Director-General, -2407, wiik@desy.de
Albrecht Wagner, Research Director, -3000, wagnera@desy.de
Ralph Eichler, H1 / ETH Zuerich, Spokesman, -2624,
eichler@mail.desy.de
Allen Caldwell, ZEUS / Columb. Univ. New York,Spokesman,
-3201, caldwell@vxdesy.desy.de
Lothar Bauerdick, ZEUS / DESY, -2459, bauerdic@vxdesy.desy.de
Wilfried Buchmueller, DESY - Theory, -2424, buchmuwi@vxdesy.desy.de
John Dainton, H1 / Liverpool, -2314, dainton@mail.desy.de Eckhard
Elsen, H1 / DESY, Deputy Spokesman, -2565,
elsen@mail.desy.de
Robert Klanner, ZEUS / Hamburg Univ., -2558, klanner@desy.de
Erich Lohrmann, ZEUS / Hamburg Univ., -3405, lohrmann@mail.desy.de
Rosario Nania, ZEUS / Bologna , -3043, nania@vxdesy.desy.de
Albert de Roeck, H1 / DESY, -2034, deroeck@mail.desy.de
Guenter Wolf, ZEUS / DESY, -3841, gwolf@mail.desy.de


General information:
Petra Folkerts, Press Officer, -3616, folkerts@desy.de

Following is from Christine Sutton a UK physicist-journalist:

From: chris (now it's 5 million) sutton <c.sutton1@physics.oxford.ac.uk>
To: G.THOMPSON@qmw.ac.uk
CC: SUTTON@av1.physics.ox.ac.uk

Hello

Below is my draft press notice with an invented embargo
to be sorted eventually! It included background info
mainly courtesy Jon Butterworth.

Remember that for the media
we have to put the excitement first (to get them interested)
and the caveats after.

cheers Chris




***********************************

**** NEWS IN PARTICLE PHYSICS *****

***********************************


Tuesday 18 February 1997
Embargoed until: 12.00 GMT 19 February 1997


HERA hints at new physics
-------------------------

Physicists working on the HERA accelerator in Hamburg,
including many from the UK, are puzzling over a small
but unexpected effect in the collisions of positrons
(anti-electrons) and protons. While it is still too early
for the researchers to be sure of what they are seeing,
the exciting possibility remains that they could be
observing a new interaction between the fundamental
building blocks of matter.

Both the major experiments at HERA - H1 and ZEUS -
observe more "events" at high energies than the
physicists can explain through known particle
interactions. Speculation abounds on what could be
causing such an effect. One exciting possibility
is that the extra events are due to a new particle,
created in the positron-proton collisions by a previously
unseen interaction between the positron and a quark,
one of the constituents of the proton.

To be certain of what they are seeing the physicists
at HERA need more data, so they are eagerly awaiting
the next start up of the accelerator, which will be
in March. During this year's run both experiments
should at least double the amount of data they have
in the interesting high energy region.



For further information please contact:


H1 experiment:

Professor Robin Marshall, University of Manchester
Tel: until Thursday evening, 00 49 8998 3615
then 0161 275 4170 or 0161 833 4415
Email: robin@m2.ph.man.ac.uk

Dr Graham Thompson, Queen Mary & Westfield College, London
Tel: 0171-975-5045 or 0181-504-7675
Email: G.Thompson@qmw.ac.uk


ZEUS experiment:

Dr Jon Butterworth, Imperial College, London
Tel: 0171 380 7318 or 0171 424 0712
Fax: 0171 380 7145
Email: J.Butterworth@ucl.ac.uk

Dr Kenneth Long
Tel: 0171-594-7812
Fax: 0171-823-8830
EMail: K.Long@IC.AC.UK

General information:

Dr Christine Sutton, University of Oxford
Tel: 01865-273322 or 01865-273353 (secretary) or 01235-850091
Fax: 01865-273418
Email: C.Sutton1@physics.oxford.ac.uk

For web pages see:

DESY & HERA: http://www.desy.de/pr-info/desy-forschung_e.html
H1: http://dice2.desy.de:80/
ZEUS: http://www-zeus.desy.de/



Background Information
--

(with thanks to Dr Jon Butterworth)


HERA
----

HERA is the Hadron-Electron Ring Accelerator, a large underground particle
accelerator at the DESY laboratory in Hamburg. The accelerator tunnel
is a ring 6.3 km long passing under a park and trotting course, as well as
the home ground of the Hamburg SV football team, in the northwest of the
city.

HERA accelerates bunches of electrons or positrons (antielectrons)
travelling in one direction round the ring, and bunches of protons
travelling in the opposite direction, before bringing the bunches to
collide head on a hundred million times a second. By meeting head on,
the protons collide with the electrons or positrons at energies a hundred
times greater than ever achieved elsewhere. This allows physicists at HERA
to make a more complete study of the internal structure of the proton than
has previously been possible.


H1 and ZEUS
-----------

H1 and ZEUS are two large detectors constructed in order to study
collisions at HERA. They have been collecting data since 1992. Both
detectors were built and are operated by multinational collaborations
of around 400 particle physicists.

Collaborating countries include Canada, France, Germany, Israel,
Italy, Japan, Korea, the Netherlands, Poland, Russia, Spain, UK and
the USA. Major parts of both experiments were constructed in the UK,
and particle physicists from the UK comprise around 20% of both
collaborations. Groups from Bristol, Glasgow, Imperial College, Oxford
and University College, London, are members of the ZEUS collaboration,
while teams from Birmingham, Lancaster, Liverpool, Manchester, and
Queen Mary and Westfield College, London, are members of H1. Physicists
from the Rutherford Appleton Laboratory in Oxfordshire participate in
both experiments.

The detectors have tracking chambers to detect the directions of
charged particles as well as large devices called calorimeters to
measure the energies of the particles produced in the collisions.
Huge superconducting magnets provide a magnetic field to bend the
charged particles and allow a measurement of their momentum to be made.

The high rate of crossings between particle bunches in HERA requires that
both the experiments have extremely sophisticated arrays of electronics
to read out and make sense of "events" (collisions) sufficiently quickly.
Large farms of computers sit at the end of the data cables, processing events
and saving the interesting ones on disks and tapes for later analysis by
physicists.


QUARKS, GLUONS AND THE PROTON
-----------------------------

The proton is one of the ubiquitous building blocks of atomic nuclei;
indeed, the nucleus of the lightest element, hydrogen, consists of
a single proton. The proton is not, however, a fundamental particle.
It is made up of three smaller particles called quarks, which are bound
together by the aptly named strong force - the strongest of nature's
fundamental forces. The quarks stick together by continually swapping
gluons (the carriers of the strong force) and other quarks and antiquarks
among themselves.

The high energies available at HERA mean that the electron (or positron)
beam probes the proton a distances small enough for the individual quarks
and gluons to be seen. In fact, the electron can hit a single quark or gluon
and knock it out of the proton. The quark and electron recoil from
each other, and the remaining quarks continue on their way almost
undisturbed. However, as the quarks separate the force between them
grows, rather like the force between the two ends of a stretched piece of
elastic. The energy of the recoil is so large that the elastic quickly
snaps, leading to more pairs of quarks at the ends of smaller pieces
of elastic. The process continues, and the end result is a spray or
jet of particles made from quarks ("hadrons") in one side of the detector,
balanced by the electron in the other side.

Much has been learnt, about the quarks and gluons inside the proton,
and the force which binds them, by studying such collisions.


HIGH X, HIGH Q2
---------------

The parameters physicists use to describe electron-proton collisions
are x and Q^2 (Q squared). In simple terms, x is the fraction of the
proton's energy that was carried by the struck quark or gluon, and Q^2
is related to the distance between the electron and the quark or gluon
at the point at which the interaction occurs. High x means very
energetic quarks, and high Q^2 means very short distances.

The experiments at HERA have made a number of important discoveries and
measurements over a very wide range x (from 0.00001 to 0.5) and Q^2
(from close to zero up to 10,000). However, the rarest and in many
ways the most interesting events are those at high Q^2 and high x,
where the most energetic quarks interact with the electron at the
smallest distances.


THE NEW RESULTS
---------------

Recenetly in this region, at high x and high Q^2, both experiments
have seen more events than expected. If the result is confirmed, this
will imply that there is something new happening in the interaction
between electrons and quarks at very small distances and high
energies. Such a new interaction is impossible to explain in the
current `Standard Model' of particle physics.

In the Standard Model, there are six quarks (down, up, strange, charm,
bottom and top, in order of increasing mass) and three charged leptons, of
which the electron is the lightest. Each charged lepton comes with an
uncharged partner - a neutrino - and all these particles come with
antiparticles of equal but opposite charge. (The positron is the antiparticle
of the electron.) There is an appealing symmetry between the six quarks
and the six leptons (including neutrinos). Yet although physicists see
many bound states (particles) composed of quarks, they never see bound
states of quarks and leptons.

In the Standard Model, quarks and leptons interact by exchanging of one of
the force carriers of the electroweak force (photons, or the W and Z bosons).
If a new interaction occurs between them, this implies either a new force
(and therefore a new force-carrying boson) or a direct interaction between
the quark and the lepton. Either could lead to a new particle which could
be created when a quark and electron come together. These new particles are
generically referred to as `leptoquarks'. They could be either a bound state
of quarks and leptons, or a new elementary particle created by the
annihilation of a quark and lepton. In either case the new particle lives
only very briefly, decaying rapidly back to the lepton and quark from which
it was created.

The fact that a new particle of this kind will have a fixed mass means
that `unexpected' events could show up at HERA around common value of x.
The data from both H1 and ZEUS suggest that this could be the case, but more
data from the forthcoming run are needed to ensure that the observed effect
is not simply a statistical fluctuation.