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"Physics Experiments"
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Junk drawer physics : 50 awesome experiments that don't cost a thing
Provides readers with more than 50 hands-on experiments that can be performed for just pennies, or less.
Book
Combination and QCD analysis of charm production cross section measurements in deep-inelastic ep scattering at HERA
Measurements of open charm production cross sections in deep-inelastic
ep
scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections
for charm production are obtained in the kinematic range of photon virtuality 2.5≤
Q
2
≤2000 GeV
2
and Bjorken scaling variable 3⋅10
−5
≤
x
≤5⋅10
−2
. The combination method accounts for the correlations of the systematic uncertainties among the different data sets. The combined charm data together with the combined inclusive deep-inelastic scattering cross sections from HERA are used as input for a detailed NLO QCD analysis to study the influence of different heavy flavour schemes on the parton distribution functions. The optimal values of the charm mass as a parameter in these different schemes are obtained. The implications on the NLO predictions for
W
±
and
Z
production cross sections at the LHC are investigated. Using the fixed flavour number scheme, the running mass of the charm quark is determined.
Journal Article
Science stunts : fun feats of physics
Contains magic tricks that are based in important physics concepts such as gravity, inertia, magnetism, sound vibrations, and more.
Book
Performance of the ATLAS Trigger System in 2010
Proton–proton collisions at
TeV and heavy ion collisions at
TeV were produced by the LHC and recorded using the ATLAS experiment’s trigger system in 2010. The LHC is designed with a maximum bunch crossing rate of 40 MHz and the ATLAS trigger system is designed to record approximately 200 of these per second. The trigger system selects events by rapidly identifying signatures of muon, electron, photon, tau lepton, jet, and
B
meson candidates, as well as using global event signatures, such as missing transverse energy. An overview of the ATLAS trigger system, the evolution of the system during 2010 and the performance of the trigger system components and selections based on the 2010 collision data are shown. A brief outline of plans for the trigger system in 2011 is presented.
Journal Article
Sensitivity of the SHiP experiment to light dark matter
A
bstract
Dark matter is a well-established theoretical addition to the Standard Model supported by many observations in modern astrophysics and cosmology. In this context, the existence of weakly interacting massive particles represents an appealing solution to the observed thermal relic in the Universe. Indeed, a large experimental campaign is ongoing for the detection of such particles in the sub-GeV mass range. Adopting the benchmark scenario for light dark matter particles produced in the decay of a dark photon, with
α
D
= 0
.
1 and
m
A
′
= 3
m
χ
, we study the potential of the SHiP experiment to detect such elusive particles through its Scattering and Neutrino detector (SND). In its 5-years run, corresponding to 2
·
10
20
protons on target from the CERN SPS, we find that SHiP will improve the current limits in the mass range for the dark matter from about 1 MeV to 300 MeV. In particular, we show that SHiP will probe the thermal target for Majorana candidates in most of this mass window and even reach the Pseudo-Dirac thermal relic.
Journal Article
Measurement of the muon flux from 400 GeV/c protons interacting in a thick molybdenum/tungsten target
The SHiP experiment is proposed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. About
10
11
muons per spill will be produced in the dump. To design the experiment such that the muon-induced background is minimized, a precise knowledge of the muon spectrum is required. To validate the muon flux generated by our Pythia and GEANT4 based Monte Carlo simulation (FairShip), we have measured the muon flux emanating from a SHiP-like target at the SPS. This target, consisting of 13 interaction lengths of slabs of molybdenum and tungsten, followed by a 2.4 m iron hadron absorber was placed in the H4 400 GeV/c proton beam line. To identify muons and to measure the momentum spectrum, a spectrometer instrumented with drift tubes and a muon tagger were used. During a 3-week period a dataset for analysis corresponding to
(
3.27
±
0.07
)
×
10
11
protons on target was recorded. This amounts to approximatively 1% of a SHiP spill.
Journal Article
A limit on the variation of the speed of light arising from quantum gravity effects
GRB 090510: a test for special relativity
Observations of the distant and short γ-ray burst GRB 090510 with the Fermi Gamma-ray Space Telescope have provided an opportunity to test a central prediction of Einstein's special theory of relativity — the Lorentz invariance. This holds that all observers measure exactly the same speed of light in a vacuum, independent of photon energy. A key test of the violation of Lorentz invariance is a possible variation of photon speed with energy. Accumulated over cosmological light-travel times, even a tiny variation in photon speed should become observable — as for instance sharp features in the light curve of a γ-ray burst. No evidence for the violation of Lorentz invariance was found in the GRB 090510 spectrum, at least down to a limit of the Planck length divided by 1.2. This argues against quantum-gravity theories where the quantum nature of space–time linearly alters the speed of light with photon energy.
Lorentz invariance — the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon energy — is a cornerstone of Einstein's special relativity, but it has been suggested that it might break near the Planck scale. A possible variation of photon speed with energy is a key test for this proposed violation; here, by studying sharp features in γ-ray burst light-curves to look for even tiny variations in photon speed, no evidence for the violation of Lorentz invariance is found.
A cornerstone of Einstein’s special relativity is Lorentz invariance—the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon-energy. While special relativity assumes that there is no fundamental length-scale associated with such invariance, there is a fundamental scale (the Planck scale,
l
Planck
≈ 1.62 × 10
-33
cm or
E
Planck
=
M
Planck
c
2
≈ 1.22 × 10
19
GeV), at which quantum effects are expected to strongly affect the nature of space–time. There is great interest in the (not yet validated) idea that Lorentz invariance might break near the Planck scale. A key test of such violation of Lorentz invariance is a possible variation of photon speed with energy
1
,
2
,
3
,
4
,
5
,
6
,
7
. Even a tiny variation in photon speed, when accumulated over cosmological light-travel times, may be revealed by observing sharp features in γ-ray burst (GRB) light-curves
2
. Here we report the detection of emission up to ∼31 GeV from the distant and short GRB 090510. We find no evidence for the violation of Lorentz invariance, and place a lower limit of 1.2
E
Planck
on the scale of a linear energy dependence (or an inverse wavelength dependence), subject to reasonable assumptions about the emission (equivalently we have an upper limit of
l
Planck
/1.2 on the length scale of the effect). Our results disfavour quantum-gravity theories
3
,
6
,
7
in which the quantum nature of space–time on a very small scale linearly alters the speed of light.
Journal Article