Abstract
Refraction between isotropic media is characterized by light bending towards the normal to the boundary when passing from a low- to a high-refractive-index medium. However, refraction ...between anisotropic media is a more exotic phenomenon which remains barely investigated, particularly at the nanoscale. Here, we visualize and comprehensively study the general case of refraction of electromagnetic waves between two strongly anisotropic (hyperbolic) media, and we do it with the use of nanoscale-confined polaritons in a natural medium: α-MoO
3
. The refracted polaritons exhibit non-intuitive directions of propagation as they traverse planar nanoprisms, enabling to unveil an exotic optical effect: bending-free refraction. Furthermore, we develop an in-plane refractive hyperlens, yielding foci as small as λ
p
/6, being λ
p
the polariton wavelength (λ
0
/50 compared to the wavelength of free-space light). Our results set the grounds for planar nano-optics in strongly anisotropic media, with potential for effective control of the flow of energy at the nanoscale.
Transverse momentum spectra,
d
2
σ
/
(
d
η
d
p
T
2
)
, of charged hadron production in
p
p
-collisions are considered in terms of a recently introduced two component model. The shapes of the particle ...distributions vary as a function of the c.m.s. energy in the collision and the measured pseudorapidity interval. As a result the pseudorapidity of a secondary hadron in the moving proton rest frame is shown to be a universal parameter describing the shape of the spectra in
pp
-collisions. In order to extract predictions on the double-differential cross sections
d
2
σ
/
(
d
η
d
p
T
2
)
of hadron production for future LHC-measurements the different sets of available experimental data have been used in this study.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Vector meson photoproduction in UPCs with FoCal Bylinkin, A; Nystrand, J; Tapia Takaki, D
Journal of physics. G, Nuclear and particle physics,
05/2023, Letnik:
50, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Abstract
We discuss the physics prospects of photon-induced measurements using the high-granularity FoCal detector to be installed at the ALICE experiment, covering the pseudorapidity interval 3.4 ≤
...η
≤ 5.8. This new detector, scheduled to be in operation from Run 4, will explore the small Bjorken-
x
physics region in an unprecedented way. In this region the gluon ,saturation phenomenon is expected to be dominant. Combined with the rest of the ALICE subdetectors, including the zero degree calorimenters, FoCal will serve to reconstruct in a model-independent way the measured photoproduction cross sections for vectors mesons in a wide range of photon-target energies, down to
x
values of about 7 × 10
−6
and 2 × 10
−6
in ultra-peripheral photon–proton and photon–lead collisions, respectively.
The shapes of invariant differential cross section for identified
π
±
,
K
±
,
p
and
p
¯
production as a function of transverse momentum measured in
p
p
collisions by the PHENIX detector are analyzed ...in terms of a recently introduced approach. Simultaneous fits of these data to the sum of exponential and power-law terms show a significant difference in the exponential term contributions. This effect qualitatively explains the observed shape of the experimental
K
/
π
and
p
/
π
yield ratios measured as a function of transverse momentum of produced hadrons. A picture with two types of mechanisms for hadron production is presented. Universality of the power-law term behavior for
π
±
,
K
±
,
p
, and
p
¯
production is shown.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The transverse-momentum dependence of inclusive differential cross sections measured in various collider experiments for processes involving the production of long-lived charged hadrons was ...approximated by the sum of an exponential and a power-law function. The dependence of the parameters appearing in these functions on the colliding-particle energy and type was studied, and relationships between these parameters were established. A number of new regularities in the behavior of charged-particle spectra were discovered.
The shape of the invariant differential cross section for charged hadron production as a function of transverse momentum measured in various collider experiments is analyzed. Contrary to the behavior ...of produced charged kaons, protons, and antiprotons, the pion spectra require an anomalously high contribution of an exponential term to describe the shape.
We develop a theory of plasmon-assisted tunneling in graphene-insulator-graphene heterostructures and reveal the manifestations of such process in current-voltage curves, plasmon emission spectra, ...and junction electroluminescence. We present a unified framework for evaluation of tunneling due to carrier-carrier Coulomb scattering and due to emission of plasmons; the latter mechanism generally dominates the full inelastic current. Moreover, the plasmon-assisted current and plasmon emission rates possess resonant peaks at voltages providing equal energies, momenta, and group velocities of collective and single-particle interlayer excitations. This resonance is unique to the tunnel-coupled 2d systems of massless electrons and is deeply related to strong interactions between collinear carriers in graphene. The predicted effect can be used for design of efficient nanoscale voltage-tunable sources of photons and surface plasmons.
In present study, we introduce graphene field-effect transistors (G-FET) fabricated on silicon - silicon dioxide wafers and analyse their properties. Electric and photoelectric effects in these ...devices were experimentally observed and discussed. We demonstrate that the understanding of the processes occurring in the substrate is of high importance not only for the development of all types of photodetectors based on field-effect transistors, but also could be used for the designing of devices with novel functionalities.
Vector meson photoproduction in UPCs with FoCal Bylinkin, A.; Nystrand, J.; Tapia Takaki, D.
Journal of physics. G, Nuclear and particle physics,
04/2023, Letnik:
50, Številka:
5
Journal Article
Recenzirano
Abstract
We discuss the physics prospects of photon-induced measurements using the high-granularity FoCal detector to be installed at the ALICE experiment, covering the pseudorapidity interval 3.4 ≤
...η
≤ 5.8. This new detector, scheduled to be in operation from Run 4, will explore the small Bjorken-
x
physics region in an unprecedented way. In this region the gluon ,saturation phenomenon is expected to be dominant. Combined with the rest of the ALICE subdetectors, including the zero degree calorimenters, FoCal will serve to reconstruct in a model-independent way the measured photoproduction cross sections for vectors mesons in a wide range of photon-target energies, down to
x
values of about 7 × 10
−6
and 2 × 10
−6
in ultra-peripheral photon–proton and photon–lead collisions, respectively.
A qualitative model for hadroproduction in high energy collisions considering two components (“thermal” and “hard”) to hadroproduction is proposed. Inclusive pseudorapidity distributions, dσ/dη, and ...transverse momentum spectra, d2σ/(dηdpT2), measured by different collaborations are considered in terms of this model. The shapes of the pseudorapidity distributions agree with that one can expect from the qualitative picture introduced. The model is used to provide predictions for the LHC. Data up to a centre-of-mass energy of 7 TeV are well described and predictions for higher energies await new data. Finally, the differences between charged particle spectra produced in inclusive and diffractive events are discussed and the absence of the “thermal” component in the latter is observed.
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