2,029 research outputs found
Quantum Walk of Two Interacting Bosons
We study the effect of interactions on the bosonic two-particle quantum walk
and its corresponding spatial correlations. The combined effect of interactions
and Hanbury-Brown Twiss interference results in unique spatial correlations
which depend on the strength of the interaction, but not on its sign. The
results are explained in light of the two-particle spectrum and the physics of
attractively and repulsively bound pairs. We experimentally measure the weak
interaction limit of these effects in nonlinear photonic lattices. Finally, we
discuss an experimental approach to observe the strong interaction limit using
single atoms in optical lattices.Comment: 4 pages, 5 figures. Comments wellcom
Bose-Fermi mixtures in 1D optical superlattices
The zero temperature phase diagram of binary boson-fermion mixtures in
two-colour superlattices is investigated. The eigenvalue problem associated
with the Bose-Fermi-Hubbard Hamiltonian is solved using an exact numerical
diagonalization technique, supplemented by an adaptive basis truncation scheme.
The physically motivated basis truncation allows to access larger systems in a
fully controlled and very flexible framework. Several experimentally relevant
observables, such as the matter-wave interference pattern and the
condensatefraction, are investigated in order to explore the rich phase
diagram. At symmetric half filling a phase similar to the Mott-insulating phase
in a commensurate purely bosonic system is identified and an analogy to recent
experiments is pointed out. Furthermore a phase of complete localization of the
bosonic species generated by the repulsive boson-fermion interaction is
identified. These localized condensates are of a different nature than the
genuine Bose-Einstein condensates in optical lattices.Comment: 18 pages, 9 figure
Numerical study of one-dimensional and interacting Bose-Einstein condensates in a random potential
We present a detailed numerical study of the effect of a disordered potential
on a confined one-dimensional Bose-Einstein condensate, in the framework of a
mean-field description. For repulsive interactions, we consider the
Thomas-Fermi and Gaussian limits and for attractive interactions the behavior
of soliton solutions. We find that the disorder average spatial extension of
the stationary density profile decreases with an increasing strength of the
disordered potential both for repulsive and attractive interactions among
bosons. In the Thomas Fermi limit, the suppression of transport is accompanied
by a strong localization of the bosons around the state k=0 in momentum space.
The time dependent density profiles differ considerably in the cases we have
considered. For attractive Bose-Einstein condensates, a bright soliton exists
with an overall unchanged shape, but a disorder dependent width. For weak
disorder, the soliton moves on and for a stronger disorder, it bounces back and
forth between high potential barriers.Comment: 13 pages, 13 figures, few typos correcte
Metal micro-detectors: development of “transparent” position sensitive detector for beam diagnostics
Metal Micro-strip Detector (MMD) represents a novel position sensitive detector for wide range of applications. The main advantages of MMD are low thickness, high radiation resistance and high spatial resolution. MMD production technology includes some stages: micro-strip layout made by photo-lithography on silicon wafer, plasma-chemistry etching of the silicon wafer in the operating window, micro-cabling connection to the readout electronics and DAQ. Commercially available read-out systems (VA_SCM3 microchip preamplifier, Time Pix readout chip, Gotthard, X-DAS) have been studied for use with MMD. Characterization studies of the MMD are presented in details.Металлический микростриповый детектор (ММД) представляет собой новый позиционно- чувствительный детектор для широкого спектра применений. Основные преимущества ММД: малая толщина, высокая радиационная стойкость, высокое пространственное разрешение. Технология производства ММД включает в себя несколько этапов: микростриповая структура создается при помощи фотолитографии на кремниевой пластине, плазмо-химическое травление кремниевой пластины в рабочем окне, подключение микро-кабелем к считывающей электронике. Коммерчески доступные системы считывания и обработки данных (VA_SCM3, TimePix, Gotthard, X-DAS) были изучены для использования с ММД. Представлены результаты исследований MMD на пучках разных частиц.Металевий мікростріповий детектор (ММД) являє собою новий позиційно-чутливий детектор для широкого спектру застосувань. Основні переваги ММД: мала товщина, висока радіаційна стійкість, висока просторова роздільна здатність. Технологія виробництва ММД включає в себе кілька етапів: мікростріпова структура створюється за допомогою фотолітографії на кремнієвій пластині, плазмо-хімічне травлення кремнієвої пластини в робочому вікні, підключення мікро-кабелем до зчитуючої електроніки. Комерційно доступні системи зчитування й обробки даних (VA_SCM3, TimePix, Gotthard, X-DAS) були вивчені для використання з ММД. Представлено результати дослідження MMD на пучках різних частинок
Theory of Thermal Motion in Electromagnetically Induced Transparency: Diffusion, Doppler, Dicke and Ramsey
We present a theoretical model for electromagnetically induced transparency
(EIT) in vapor, that incorporates atomic motion and velocity-changing
collisions into the dynamics of the density-matrix distribution. Within a
unified formalism we demonstrate various motional effects, known for EIT in
vapor: Doppler-broadening of the absorption spectrum; Dicke-narrowing and
time-of-flight broadening of the transmission window for a finite-sized probe;
Diffusion of atomic coherence during storage of light and diffusion of the
light-matter excitation during slow-light propagation; and Ramsey-narrowing of
the spectrum for a probe and pump beams of finite-size.Comment: Reference added, typos correcte
Adverse clinical sequelae after skin branding: a case series
This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions
The HERA-B collaboration has studied the production of charmonium and open
charm states in collisions of 920 GeV protons with wire targets of different
materials. The acceptance of the HERA-B spectrometer covers negative values of
xF up to xF=-0.3 and a broad range in transverse momentum from 0.0 to 4.8
GeV/c. The studies presented in this paper include J/psi differential
distributions and the suppression of J/psi production in nuclear media.
Furthermore, production cross sections and cross section ratios for open charm
mesons are discussed.Comment: 5 pages, 9 figures, to be published in the proceedings of the 6th
International Conference on Hyperons, Charm & Beauty Hadrons (BEACH04),
Chicago, IL, June 27 - July 3, 200
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a
centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The
value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08
^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical,
the second systematic and the third is associated to the ratio of fragmentation
fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/-
0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be
(3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table
Measurement of the CKM angle γ from a combination of B±→Dh± analyses
A combination of three LHCb measurements of the CKM angle γ is presented. The decays B±→D K± and
B±→Dπ± are used, where D denotes an admixture of D0 and D0 mesons, decaying into K+K−, π+π−, K±π∓, K±π∓π±π∓, K0Sπ+π−, or K0S K+K− final states. All measurements use a dataset corresponding to 1.0 fb−1 of integrated luminosity. Combining results from B±→D K± decays alone a best-fit value of
γ =72.0◦ is found, and confidence intervals are set
γ ∈ [56.4,86.7]◦ at 68% CL,
γ ∈ [42.6,99.6]◦ at 95% CL.
The best-fit value of γ found from a combination of results from B±→Dπ± decays alone, is γ =18.9◦,
and the confidence intervals
γ ∈ [7.4,99.2]◦ ∪ [167.9,176.4]◦ at 68% CL
are set, without constraint at 95% CL. The combination of results from B± → D K± and B± → Dπ±
decays gives a best-fit value of γ =72.6◦ and the confidence intervals
γ ∈ [55.4,82.3]◦ at 68% CL,
γ ∈ [40.2,92.7]◦ at 95% CL
are set. All values are expressed modulo 180◦, and are obtained taking into account the effect of D0–D0
mixing
Differential branching fraction and angular analysis of the decay B0→K∗0μ+μ−
The angular distribution and differential branching fraction of the decay B 0→ K ∗0 μ + μ − are studied using a data sample, collected by the LHCb experiment in pp collisions at s√=7 TeV, corresponding to an integrated luminosity of 1.0 fb−1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
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