The Mudcat Café TM
Thread #59418 Message #1981301
Posted By: Amos
27-Feb-07 - 07:42 PM
Thread Name: BS: The Mother of all BS threads
Subject: RE: BS: The Mother of all BS threads
Nor are the mysteries of feminine unpredictability the only thing being laid bare by science this week. Observe!
STRING THEORY EXPLAINS RHIC JET SUPPRESSION. String theory argues
that all matter is composed of string-like shreds in a
10-dimensional hyperspace assembled in various forms. It has won
acclaim from many who appreciate the theory‚s elegant mathematics
and ambition to unite quantum mechanics and general relativity, and
skepticism from others who cite the theory‚s lack of a practical
track record. String theory, the doubters say, makes no testable
predictions.
But this isn‚t exactly true. Indeed, the theory has not yet been
experimentally vindicated in the realm of quantum gravity, but has
been put into play in the realm of high-energy ion collisions, the
kind carried out at Brookhaven‚s Relativistic Heavy Ion Collider
(RHIC). A few years ago string practitioners attempted to establish
a relationship between the 10-dimensional string world and the
4-dimensional (3 spatial dimensions plus time) world in which we
observe interactions among quark-filled particles like protons (for
background, see Physics Today, May 2005).
This duality between
string theory and the theory of the strong nuclear force, quantum
chromodynamics (QCD), was recently used to interpret puzzling early
results from RHIC, namely the suppression of energetic quark jets
that should have emerged from the fireball formed when two heavy
nuclei (such as gold) collide head on. The thinking was that
perhaps the plasma of quarks and gluons (quarks bursting free from
their customary proton and meson groupings) wasn‚t a gas of weakly
interacting particles (as was originally thought) but a gas of
strongly interacting particles, so strong that any energetic quarks
that might have escaped the fireball (initiating a secondary
avalanche, or jet, or quarks) would quickly be slowed and stripped
of energy on its way through the tumultuous quark-gluon plasma (QGP)
environment.
Two new papers by Hong Liu and Krishna Rajagopal of (MIT) and Urs
Wiedemann (CERN) address this problem. The first paper calculates a
specific quark-suppression parameter (namely, how much the quarks,
each attached to a string dangling "downward" into a fifth
dimension, are pushed around as they traverse the quark-gluon
plasma) that agrees closely with the experimentally observed value.
Rajagopal (krishna@ctp.mit.edu, 617-253-6202) says that in the
second paper, the same authors make a specific testable prediction
using string theory that bears not just on missing jets of energetic
light quarks (up, down, and strange quarks), but on the melting or
dissociation temperatures of bound states of heavy quarks
(charm-anticharm or bottom-antibottom pairs) moving through the
quark-gluon plasma with sufficiently high velocity, as will be
produced in future experiments at RHIC and the Large Hadron Collider
(LHC) under construction at CERN.
I CAN'T WAIT!!
A