Re: [Brahms-l] Physics News Update 728 (fwd)

Hi Peter,
I have actually not know about this web page. I general we now point to the
pictures of events that are much nice  e.g.
http://server.c-ad.bnl.gov/esfd/RMEM/event_brahms.GIF
which I think is much better.

regards
    Flemming

----------------------------------------------------------------
Flemming Videbaek
Physics Department
Brookhaven National Laboratory

e-mail: videbaek@bnl.gov
phone: 631-344-4106
----- Original Message ----- 
From: "Peter H.L. Christiansen" <pchristi@nbi.dk>
To: "brahms-l" <brahms-l@lists.bnl.gov>
Sent: Thursday, April 21, 2005 3:31 AM
Subject: [Brahms-l] Physics News Update 728 (fwd)


> Hi,
>
> A long story about the RHIC whitepapers in the Physics News Update. Maybe
> we could change the picture on the web page for BRAHMS to resemble
> something a bit more Hubble quality like;)
>
> Cheers,
>    Peter
>
> -- 
> :-) --------------------------- )-:
>  Peter H L Christiansen
>  pchristi@nbi.dk / (+41)764870425
> :-D --------------------------- \-:
>
> ---------- Forwarded message ----------
> Date: Wed, 20 Apr 2005 10:42:37 -0400
> From: physnews@aip.org
> To: pchristi@NBI.DK
> Subject: Physics News Update 728
>
> PHYSICS NEWS UPDATE
> The American Institute of Physics Bulletin of Physics News
> Number 728 April 20, 2005  by Phillip F. Schewe, Ben Stein
>
> AN OCEAN OF QUARKS.  Nuclear physicists have now demonstrated that
> the material essence of the universe at a time mere microseconds
> after the big bang consists of a ubiquitous quark-gluon liquid.
> This huge insight comes from an experiment carried out over the past
> five years at the Relativistic Heavy Ion Collider (RHIC), the giant
> crusher of nuclei located at Brookhaven National Lab, where
> scientists have created a toy version of the cosmos amid high-energy
> collisions.  RHIC is of course not a telescope pointed at the sky
> but an underground accelerator on Long Island; it is, nevertheless,
> in effect, a precision cosmology instrument for viewing a very early
> portion of the universe, a wild era long before the time of the
> first atoms (which formed about 400,000 years after the big bang),
> before the first compound nuclei such as helium (about a minute
> after the big bang), before even the time when protons are thought
> to have formed into stable entities (ten microseconds).
>
> In our later, cooler epoch quarks conventionally occur in groups of
> two or three.  These groupings, called mesons and baryons,
> respectively, are held together by particles called gluons---which
> act as agents for the strong nuclear force.  Baryons (such as
> protons and neutrons), collectively called hadrons, are the normal
> building blocks of any nucleus.  Could hadrons be melted or smashed
> into their component quarks through violent means?  Could a nucleus
> be made to rupture and spill its innards into a common swarm of
> unconfined quarks and gluons?  This is what RHIC set out to show.
>
> Let's look at what happened.  In the RHIC accelerator itself two
> beams of gold ions, atoms stripped of all their electrons, are
> clashed at several interaction zones around the ring-shaped
> facility.  Every nucleus is a bundle of 197 protons and neutrons,
> each of which shoots along with an energy of up to 100 GeV.
> Therefore, when the two gold projectiles meet in a head-on "central
> collision" event, the total collision energy is 40 TeV (40 trillion
> electron volts).  Of this, typically 25 TeV serves as a stock of
> surplus energy---call it a fireball---out of which new particles can
> be created.   Indeed in many gold-gold smashups as many as 10,000
> new particles are born of that fireball.  Hubble-quality pictures of
> this blast of particles
> (http://www.bnl.gov/RHIC/full_en_images.htm), shows the aftermath of
> the fireball, but not the fireball itself.
>
> The outward streaming particles provide all the forensic evidence
> for determining the properties of the fireball.  To harvest this
> debris, the RHIC detectors must be agile and very fast. The
> recreation of the frenzied quark era is ephemeral, lasting only a
> few times 10^-24 seconds. The size of the fireball is about 5
> femtometers, its density about 100 times that of an ordinary
> nucleus, and its temperature about 2 trillion degrees Kelvin or (in
> energy units) 175 MeV.  RHIC was built to create that fireball.  But
> was it the much-anticipated quark-gluon plasma?  The data
> unexpectedly showed that the fireball looked nothing like a gas.
> For one thing, potent jets of mesons and protons expected to be
> squirting out of the fireball, were being suppressed.
>
> Now, for the first time since starting nuclear collisions at RHIC in
> the year 2000 and with plenty of data in hand, all four detector
> groups operating at the lab have converged on a consensus opinion.
> They believe that the fireball is a liquid of strongly interacting
> quarks and gluons rather than a gas of weakly interacting quarks and
> gluons.  The RHIC findings were reported at this week's April
> meeting of the American Physical Society (APS) in Tampa, Florida in
> a talk delivered by Gary Westfall (Michigan State) and at a press
> conference attended by several RHIC scientists.
>
> Brookhaven physicist Samuel Aronson said that having established the
> quark-gluon-liquid nature of the pre-protonic universe, RHIC
> expected to plumb the liquid's properties, such as its heat capacity
> and its reaction to shock waves.  The liquid is dense but seems to
> flow with very little viscosity.  It flows so freely that it
> approximates an ideal, or perfect, fluid, the kind governed by the
> standard laws of hydrodynamics.  At least in its flow properties the
> quark liquid is therefore a classical liquid and should not be
> confused with a superfluid, whose flow properties (including zero
> viscosity) are dictated by quantum mechanics.
>
> One of the reasons for RHIC's previous hesitancy in delivering a
> definitive pronouncement was concern over the issue of whether the
> observed nuclear liquid was composed of truly deconfined quarks and
> gluons or of quarks confined within hadrons, or maybe even a mixture
> of quarks and hadrons.  According to William Zajc (Columbia Univ.
> and spokesperson for the PHENIX detector group at RHIC), the
> patterns of particles flying out of the fireball, including
> preliminary data on heavier, charm-quark-containing particles such
> as D mesons, support the quark liquid picture.
>
> To summarize, the main stories here are (1) that based on the
> evidence of the RHIC data, the universe in the microsecond era would
> seem to consist of a novel liquid of quarks and gluons; (2) that
> RHIC has reproduced small fragments of this early phase of the
> universe for detailed study; and (3) that these results are vouched
> for by all four RHIC groups.  If there had been delays in making an
> announcement of the results or if the exact nomenclature for the
> novel nuclear matter had been left unsettled, the RHIC physicists at
> the press conference seemed more interested in pursuing their new
> kind of experimental science---a sort of fluid-dynamical cosmology.
>
> (All four groups are also concurrently publishing  "white paper"
> summaries of their work in the journal Nuclear Physics A.  Preprints
> are available as follows: BRAHMS,
> http://arxiv.org/abs/nucl-ex/0410020 ; PHENIX,
> http://arxiv.org/abs/nucl-ex/0410003 ; PHOBOS,
> http://arxiv.org/abs/nucl-ex/0410022 ; and STAR,
> http://arxiv.org/abs/nucl-ex/0501009)
>
> ***********
> PHYSICS NEWS UPDATE is a digest of physics news items arising
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