Abstract
The TOTEM experiment at the LHC has performed the first measurement at
$$\sqrt{s} = 13\,\mathrm{TeV}$$
s
=
13
TeV
of the
$$\rho $$
ρ
parameter, the real to imaginary ratio of the nuclear ...elastic scattering amplitude at
$$t=0$$
t
=
0
, obtaining the following results:
$$\rho = 0.09 \pm 0.01$$
ρ
=
0.09
±
0.01
and
$$\rho = 0.10 \pm 0.01$$
ρ
=
0.10
±
0.01
, depending on different physics assumptions and mathematical modelling. The unprecedented precision of the
$$\rho $$
ρ
measurement, combined with the TOTEM total cross-section measurements in an energy range larger than
$$10\,\mathrm{TeV}$$
10
TeV
(from 2.76 to
$$13\,\mathrm{TeV}$$
13
TeV
), has implied the exclusion of all the models classified and published by COMPETE. The
$$\rho $$
ρ
results obtained by TOTEM are compatible with the predictions, from other theoretical models both in the Regge-like framework and in the QCD framework, of a crossing-odd colourless 3-gluon compound state exchange in the
t
-channel of the proton–proton elastic scattering. On the contrary, if shown that the crossing-odd 3-gluon compound state
t
-channel exchange is not of importance for the description of elastic scattering, the
$$\rho $$
ρ
value determined by TOTEM would represent a first evidence of a slowing down of the total cross-section growth at higher energies. The very low-|
t
| reach allowed also to determine the absolute normalisation using the Coulomb amplitude for the first time at the LHC and obtain a new total proton–proton cross-section measurement
$$\sigma _{\mathrm{tot}} = (110.3 \pm 3.5)\,\mathrm{mb}$$
σ
tot
=
(
110.3
±
3.5
)
mb
, completely independent from the previous TOTEM determination. Combining the two TOTEM results yields
$$\sigma _{\mathrm{tot}} = (110.5 \pm 2.4)\,\mathrm{mb}$$
σ
tot
=
(
110.5
±
2.4
)
mb
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract The TOTEM experiment at the LHC has performed the first measurement at $$\sqrt{s} = 13\,\mathrm{TeV}$$ s=13TeV of the $$\rho $$ ρ parameter, the real to imaginary ratio of the nuclear ...elastic scattering amplitude at $$t=0$$ t=0 , obtaining the following results: $$\rho = 0.09 \pm 0.01$$ ρ=0.09±0.01 and $$\rho = 0.10 \pm 0.01$$ ρ=0.10±0.01 , depending on different physics assumptions and mathematical modelling. The unprecedented precision of the $$\rho $$ ρ measurement, combined with the TOTEM total cross-section measurements in an energy range larger than $$10\,\mathrm{TeV}$$ 10TeV (from 2.76 to $$13\,\mathrm{TeV}$$ 13TeV ), has implied the exclusion of all the models classified and published by COMPETE. The $$\rho $$ ρ results obtained by TOTEM are compatible with the predictions, from other theoretical models both in the Regge-like framework and in the QCD framework, of a crossing-odd colourless 3-gluon compound state exchange in the t-channel of the proton–proton elastic scattering. On the contrary, if shown that the crossing-odd 3-gluon compound state t-channel exchange is not of importance for the description of elastic scattering, the $$\rho $$ ρ value determined by TOTEM would represent a first evidence of a slowing down of the total cross-section growth at higher energies. The very low-|t| reach allowed also to determine the absolute normalisation using the Coulomb amplitude for the first time at the LHC and obtain a new total proton–proton cross-section measurement $$\sigma _{\mathrm{tot}} = (110.3 \pm 3.5)\,\mathrm{mb}$$ σtot=(110.3±3.5)mb , completely independent from the previous TOTEM determination. Combining the two TOTEM results yields $$\sigma _{\mathrm{tot}} = (110.5 \pm 2.4)\,\mathrm{mb}$$ σtot=(110.5±2.4)mb .
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The NA60 experiment has studied low-mass muon pair production in proton–nucleus collisions with a system of Be, Cu, In, W, Pb and U targets, using a 400 GeV proton beam at the CERN SPS. The ...transverse momentum spectra of the
ρ
/
ω
and
ϕ
mesons are measured in the full
p
T
range accessible, from
p
T
=
0
up to
2
GeV/c
. The nuclear dependence of the production cross sections of the
η
,
ω
and
ϕ
mesons has been found to be consistent with the power law
σ
pA
∝
A
α
, with the
α
parameter increasing as a function of
p
T
for all the particles, and an approximate hierarchy
α
η
≈
α
ϕ
>
α
ω
. The cross section ratios
σ
η
/
σ
ω
,
σ
ρ
/
σ
ω
and
σ
ϕ
/
σ
ω
have been studied as a function of the size A of the production target, and an increase of the
η
and
ϕ
yields relative to the
ω
is observed from p–Be to p–U collisions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Precise knowledge of the beam optics at the LHC is crucial to fulfill the physics goals of the TOTEM experiment, where the kinematics of the scattered protons is reconstructed with near-beam ...telescopes-so-called Roman pots (RP). Before being detected, the protons' trajectories are influenced by the magnetic fields of the accelerator lattice. Thus precise understanding of the proton transport is of key importance for the experiment. A novel method of optics evaluation is proposed which exploits kinematical distributions of elastically scattered protons observed in the RPs. Theoretical predictions, as well as Monte Carlo studies, show that the residual uncertainty of the optics estimation method is smaller than .
The NA60 experiment studies muon pair production with proton and Indium beams. It is a second generation experiment, designed to answer specific questions left open, in the leptonic sector, by the ...previous round of SPS experiments, finished in 2000. The results presented in this paper cover the dimuon invariant mass range from the threshold to the J/
ψ. The main physics topics that we address include the in-medium modifications of the
ρ meson, the origin of the dimuon excess observed between the
ϕ and the J/
ψ, and the study of the anomalous J/
ψ suppression. For each of these subjects, the NA60 results represent a significant step forward towards a deeper understanding of the physics of heavy ion collisions at SPS energies.
The NA60 experiment has studied J/ψ production in p–A collisions at 158 and 400 GeV, at the CERN SPS. Nuclear effects on the J/ψ yield have been estimated from the A-dependence of the production ...cross section ratios σJ/ψA/σJ/ψBe (A=Al, Cu, In, W, Pb, U). We observe a significant nuclear suppression of the J/ψ yield per nucleon–nucleon collision, with a larger effect at lower incident energy, and we compare this result with previous observations by other fixed-target experiments. An attempt to disentangle the different contributions to the observed suppression has been carried out by studying the dependence of nuclear effects on x2, the fraction of the nucleon momentum carried by the interacting parton in the target nucleus.
The pseudorapidity density of charged particles dN
c
h
/d
η
is measured by the TOTEM experiment in proton–proton collisions at
s
=
8
TeV within the range
3.9
<
η
<
4.7
and
-
6.95
<
η
<
-
6.9
. Data ...were collected in a low intensity LHC run with collisions occurring at a distance of 11.25 m from the nominal interaction point. The data sample is expected to include 96–97 % of the inelastic proton–proton interactions. The measurement reported here considers charged particles with
p
T
>
0
MeV/c, produced in inelastic interactions with at least one charged particle in
-
7
<
η
<
-
6
or
3.7
<
η
<
4.8
. The dN
c
h
/d
η
has been found to decrease with
|
η
|
, from 5.11
±
0.73 at
η
=
3.95
to 1.81
±
0.56 at
η
=
-
6.925. Several Monte Carlo generators are compared to the data and are found to be within the systematic uncertainty of the measurement.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The TOTEM collaboration has measured the proton–proton total cross section at s√=13 TeV with a luminosity-independent method. Using dedicated β*=90 m beam optics, the Roman Pots were inserted very ...close to the beam. The inelastic scattering rate has been measured by the T1 and T2 telescopes during the same LHC fill. After applying the optical theorem the total proton–proton cross section is σtot=(110.6 ± 3.4 ) mb, well in agreement with the extrapolation from lower energies. This method also allows one to derive the luminosity-independent elastic and inelastic cross sections σel=(31.0 ± 1.7) mb and σinel=(79.5 ± 1.8) mb .
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The TOTEM collaboration has measured the proton-proton total cross section at Formula omitted with a luminosity-independent method. Using dedicated Formula omitted beam optics, the Roman Pots were ...inserted very close to the beam. The inelastic scattering rate has been measured by the T1 and T2 telescopes during the same LHC fill. After applying the optical theorem the total proton-proton cross section is Formula omitted) mb, well in agreement with the extrapolation from lower energies. This method also allows one to derive the luminosity-independent elastic and inelastic cross sections: Formula omitted and Formula omitted.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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