The TOTEM collaboration has measured the proton-proton total cross section at √s=8 TeV using a luminosity-independent method. In LHC fills with dedicated beam optics, the Roman pots have been ...inserted very close to the beam allowing the detection of ~90% of the nuclear elastic scattering events. Simultaneously the inelastic scattering rate has been measured by the T1 and T2 telescopes. By applying the optical theorem, the total proton-proton cross section of (101.7±2.9) mb has been determined, well in agreement with the extrapolation from lower energies. This method also allows one to derive the luminosity-independent elastic and inelastic cross sections: σ(el)=(27.1±1.4) mb; σ(inel)=(74.7±1.7) mb.
Although elastic scattering of nucleons may look like a simple process, it presents a long-lasting challenge for theory. Due to missing hard energy scale, the perturbative QCD cannot be applied. ...Instead, many phenomenological/theoretical models have emerged. In this paper we present a unified implementation of some of the most prominent models in a C++ library, moreover extended to account for effects of the electromagnetic interaction. The library is complemented with a number of utilities. For instance, programs to sample many distributions of interest in four-momentum transfer squared, t, impact parameter, b, and collision energy s. These distributions at ISR, Spp̄S, RHIC, Tevatron and LHC energies are available for download from the project web site. Both in the form of ROOT files and PDF figures providing comparisons among the models. The package includes also a tool for Monte-Carlo generation of elastic scattering events, which can easily be embedded in any other program framework.
Program title: Elegent
Catalogue identifier: AERT_v1_0
Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AERT_v1_0.html
Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland
Licensing provisions: GNU General Public License, version 3
No. of lines in distributed program, including test data, etc.: 10551
No. of bytes in distributed program, including test data, etc.: 126316
Distribution format: tar.gz
Programming language: C++.
Computer: Any in principle, tested on x86-64 architecture.
Operating system: Any in principle, tested on GNU/Linux.
RAM: Strongly depends on the task, but typically below 20MB
Classification: 11.6.
External routines: ROOT, HepMC
Nature of problem:
Monte-Carlo simulation of elastic nucleon–nucleon collisions
Solution method:
Implementation of some of the most prominent phenomenological/theoretical models providing cumulative distribution function that is used for random event generation.
Running time:
Strongly depends on the task, but typically below 1 h.
Tree mortality can fundamentally affect soils, which in turn shape forest regeneration and dynamics. Here, we quantify the dynamics of soil volumes associated with tree mortality, parsing effects by ...mode of tree death (broken vs uprooted) and species. The concept of ecosystem biogeomorphic succession was also tested. We used repeated tree censuses carried out in ten European and North American forests, differing in species composition, climate, and disturbance regimes. Development of more than 172,000 individual trees was recorded over periods of up to 48 years, during which more than one-third of the trees died. Biogeomorphic impact of deaths was modeled using allometry and field measurements. Tree uprooting-related soil volumes accounted annually for 0.01–13.5 m
3
ha
−1
, reaching maximum values on sites with infrequent strong windstorms (European mountains). The redistribution of soils related to trees that died standing ranged annually between 0.17 and 20.7 m
3
ha
−1
and were highest in the presence of non-stand-replacing fire (Yosemite National Park, USA). Comparison of the results with known long-term erosion rates suggests that on certain sites over the last few millennia, tree uprooting may represent a significant driver of landscape erosion. Despite the key role of severe disturbances, the data showed potential for future increases in the intensity of biogeomorphic processes. The high biogeomorphic potential in some USA sites that has not yet been realized can be activated by external changes in the disturbance regime. Forests in Central Europe, on the other hand, are more sensitive to changes in biogeomorphic processes due to species turnover.
The TOTEM collaboration at the CERN LHC has measured the differential cross-section of elastic proton–proton scattering at
s
=
8
TeV
in the squared four-momentum transfer range
0.2
GeV
2
<
|
t
|
<
...1.9
GeV
2
. This interval includes the structure with a diffractive minimum (“dip”) and a secondary maximum (“bump”) that has also been observed at all other LHC energies, where measurements were made. A detailed characterisation of this structure for
s
=
8
TeV
yields the positions,
|
t
|
dip
=
(
0.521
±
0.007
)
GeV
2
and
|
t
|
bump
=
(
0.695
±
0.026
)
GeV
2
, as well as the cross-section values,
d
σ
/
d
t
dip
=
(
15.1
±
2.5
)
μ
b
/
GeV
2
and
d
σ
/
d
t
bump
=
(
29.7
±
1.8
)
μ
b
/
GeV
2
, for the dip and the bump, respectively.
Abstract
The TOTEM collaboration at the CERN LHC has measured the differential cross-section of elastic proton–proton scattering at
$$\sqrt{s} = 8\,\mathrm{TeV}$$
s
=
8
TeV
in the squared ...four-momentum transfer range
$$0.2\,\mathrm{GeV^{2}}< |t| < 1.9\,\mathrm{GeV^{2}}$$
0.2
GeV
2
<
|
t
|
<
1.9
GeV
2
. This interval includes the structure with a diffractive minimum (“dip”) and a secondary maximum (“bump”) that has also been observed at all other LHC energies, where measurements were made. A detailed characterisation of this structure for
$$\sqrt{s} = 8\,\mathrm{TeV}$$
s
=
8
TeV
yields the positions,
$$|t|_{\mathrm{dip}} = (0.521 \pm 0.007)\,\mathrm{GeV^2}$$
|
t
|
dip
=
(
0.521
±
0.007
)
GeV
2
and
$$|t|_{\mathrm{bump}} = (0.695 \pm 0.026)\,\mathrm{GeV^2}$$
|
t
|
bump
=
(
0.695
±
0.026
)
GeV
2
, as well as the cross-section values,
$$\left. {\mathrm{d}\sigma /\mathrm{d}t}\right| _{\mathrm{dip}} = (15.1 \pm 2.5)\,\mathrm{{\mu b/GeV^2}}$$
d
σ
/
d
t
dip
=
(
15.1
±
2.5
)
μ
b
/
GeV
2
and
$$\left. {\mathrm{d}\sigma /\mathrm{d}t}\right| _{\mathrm{bump}} = (29.7 \pm 1.8)\,\mathrm{{\mu b/GeV^2}}$$
d
σ
/
d
t
bump
=
(
29.7
±
1.8
)
μ
b
/
GeV
2
, for the dip and the bump, respectively.
The proton–proton elastic differential cross section
d
σ
/
d
t
has been measured by the TOTEM experiment at
s
=
2.76
TeV
energy with
β
∗
=
11
m
beam optics. The Roman Pots were inserted to 13 times ...the transverse beam size from the beam, which allowed to measure the differential cross-section of elastic scattering in a range of the squared four-momentum transfer (|
t
|) from 0.36 to
0.74
GeV
2
. The differential cross-section can be described with an exponential in the |
t
|-range between 0.36 and
0.54
GeV
2
, followed by a diffractive minimum (dip) at
|
t
dip
|
=
(
0.61
±
0.03
)
GeV
2
and a subsequent maximum (bump). The ratio of the
d
σ
/
d
t
at the bump and at the dip is
1.7
±
0.2
. When compared to the proton–antiproton measurement of the D0 experiment at
s
=
1.96
TeV
, a significant difference can be observed. Under the condition that the effects due to the energy difference between TOTEM and D0 can be neglected, the result provides evidence for the exchange of a colourless C-odd three-gluon compound state in the
t
-channel of the proton–proton and proton–antiproton elastic scattering.
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