622 research outputs found
Probing Brane-World Scenarios with Vacuum Refraction of Light Using Gamma-Ray Bursts
We argue that in fat brane-world scenarios the light propagating in vacuum will, because of massive ``Kaluza--Klein'' (KK) excitations, experience a refraction. The motion of a photon inside a fat brane can be decomposed in the longitudinal and transverse directions with respect to the surface of the brane. Since the light observable propagation is related only with the longitudinal motion, the obsered speed of light depends on the value of the momentum transverse fraction contributing as the massive KK excitations. This is directly connected with the energy of the particles emitting the light, and hence with the frequency of the light itself. Using recent results on the arrival times of radiation of different energies from the measurements of gamma-ray bursters with known redshifts, we establish the limit M>620 TeV on the inverse thickness of the brane, and thus on the masses of the KK excitations. This limit exceeds by at least one order of magnitude the typical energy scale currently in use to characterize brane phenomena in the realm of future colliders
Information-theoretic principle entails orthomodularity of a lattice
Quantum logical axiomatic systems for quantum theory usually include a
postulate that a lattice under consideration is orthomodular. We propose a
derivation of orthomodularity from an information-theoretic axiom. This
provides conceptual clarity and removes a long-standing puzzle about the
meaning of orthomodularity.Comment: Version prior to published, with slight modification
Photon mass limits from fast radio bursts
International audienceThe frequency-dependent time delays in fast radio bursts (FRBs) can be used to constrain the photon mass, if the FRB redshifts are known, but the similarity between the frequency dependences of dispersion due to plasma effects and a photon mass complicates the derivation of a limit on mÎł. The dispersion measure (DM) of FRB 150418 is known to âź0.1%, and there is a claim to have measured its redshift with an accuracy of âź2%, but the strength of the constraint on mÎł is limited by uncertainties in the modelling of the host galaxy and the Milky Way, as well as possible inhomogeneities in the intergalactic medium (IGM). Allowing for these uncertainties, the recent data on FRB 150418 indicate that mÎłâ˛1.8Ă10â14 eVcâ2 (3.2Ă10â50 kg), if FRB 150418 indeed has a redshift z=0.492 as initially reported. In the future, the different redshift dependences of the plasma and photon mass contributions to DM can be used to improve the sensitivity to mÎł if more FRB redshifts are measured. For a fixed fractional uncertainty in the extra-galactic contribution to the DM of an FRB, one with a lower redshift would provide greater sensitivity to mÎł
Two-particle angular correlations in the search for new physics at future colliders
The analysis of angular particle correlations can yield valuable insights
into the initial state of matter in high-energy collisions, thereby potentially
revealing the existence of Beyond the Standard Model scenarios such as Hidden
Valley (HV). In this study, we focus on a QCD-like hidden sector with
relatively massive HV quarks (~GeV) which might enlarge and
strengthen azimuthal correlations of final-state SM hadrons. In particular, we
study the formation and possible observation of \textit{ridge-like} structures
in the angular two-particle correlation function at future colliders,
with a much cleaner environment than in hadron colliders, such as the LHC.Comment: Talk presented at the International Workshop on Future Linear
Colliders (LCWS 2023), 15-19 May 2023. C23-05-15.
Colon cancer associated transcript-1 (CCAT1) expression in adenocarcinoma of the stomach
Background: Long non-coding RNAs (lncRNAs) have been shown to have functional roles in cancer biology and are dys-regulated in many tumors. Colon Cancer Associated Transcript -1 (CCAT1) is a lncRNA, previously shown to be significantly up-regulated in colon cancer. The aim of this study is to determine expression levels of CCAT1 in gastric carcinoma (GC). Methods: Tissue samples were obtained from patients undergoing resection for gastric carcinoma (n=19). For each patient, tumor tissue and normal appearing gastric mucosa were taken. Normal gastric tissues obtained from morbidly obese patients, undergoing laparoscopic sleeve gastrectomy served as normal controls (n=19). A human gastric carcinoma cell line (AGS) served as positive control. RNA was extracted from all tissue samples and CCAT1 expression was analyzed using quantitative real time-PCR (qRT-PCR). Results: Low expression of CCAT1 was identified in normal gastric mucosa samples obtained from morbidly obese patients [mean Relative Quantity (RQ) = 1.95¹0.4]. AGS human gastric carcinoma cell line showed an elevated level of CCAT1 expression (RQ=8.02). Expression levels of CCAT1 were approximately 10.8 fold higher in GC samples than in samples taken from the negative control group (RQ=21.1¹5 vs. RQ=1.95¹0.4, respectively, p<0.001). Interestingly, CCAT1 expression was significantly overexpressed in adjacent normal tissues when compared to the negative control group (RQ = 15.25¹2 vs. RQ=1.95¹0.4, respectively, p<0.001). Tissues obtained from recurrent GC cases showed the highest expression levels (RQ = 88.8¹31; p<0.001). Expression levels increased with tumor stage (T4- 36.4¹15, T3- 16.1¹6, T2- 4.7¹1), however this did not reach statistical significance (p=0.2). There was no difference in CCAT1 expression between intestinal and diffuse type GC (RQ=22.4¹7 vs. 22.4¹16, respectively, p=0.9). Within the normal gastric tissue samples, no significant difference in CCAT1 expression was observed in helicobacter pylori negative and positive patients (RQ= 2.4¹0.9 vs. 0.93¹0.2, respectively, p=0.13). Conclusion: CCAT1 is up-regulated in gastric cancer, and may serve as a potential bio-marker for early detection and surveillance. Š Ivyspring International Publisher
Phthalates: Potential sources and control measures
The issue of endocrine disruptors is a subject of debate in the agri-food sector and questioning for consumers through the media. Among these compounds, some of the family of phthalates, are used in the composition of some materials used in wineries. This makes it a worrying issue in terms of image and safety. The objective ok this work was to identify the sources of phthalates and the factors favoring their diffusion in wines to propose preventive and curative solutions to the wine makers. The modalities were therefore selected in different French wine regions to represent the diversity of oenological practices. This survey also led to examine more thoroughly the parameters involved in the situations that favored migration of the highest levels. Additional experiments were performed specifically on certain sources or contributing factors. The first identified sources include epoxy resin, fiberglass reinforced polyester as well as PVC materials (pipes âŚ). Favorable factors include alcohol content, temperature, duration and contact area
Remark on a Group-Theoretical Formalism for Quantum Mechanics and the Quantum-to-Classical Transition
We sketch a group-theoretical framework, based on the Heisenberg-Weyl group,
encompassing both quantum and classical statistical descriptions of mechanical
systems. We re-define in group-theoretical terms the kinematical arena and the
state-space of the system, achieving a unified quantum-classical language and a
novel version of the correspondence principle. We briefly discuss the structure
of observables and dynamics within our framework.Comment: final versio
Bose-Einstein Correlations of Three Charged Pions in Hadronic Z^0 Decays
Bose-Einstein Correlations (BEC) of three identical charged pions were
studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP.
The genuine three-pion correlations, corrected for the Coulomb effect, were
separated from the known two-pion correlations by a new subtraction procedure.
A significant genuine three-pion BEC enhancement near threshold was observed
having an emitter source radius of r_3 = 0.580 +/- 0.004 (stat.) +/- 0.029
(syst.) fm and a strength of \lambda_3 = 0.504 +/- 0.010 (stat.) +/- 0.041
(syst.). The Coulomb correction was found to increase the \lambda_3 value by
\~9% and to reduce r_3 by ~6%. The measured \lambda_3 corresponds to a value of
0.707 +/- 0.014 (stat.) +/- 0.078 (syst.) when one takes into account the
three-pion sample purity. A relation between the two-pion and the three-pion
source parameters is discussed.Comment: 19 pages, LaTeX, 5 eps figures included, accepted by Eur. Phys. J.
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
Standalone vertex ďŹnding in the ATLAS muon spectrometer
A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at âs = 7 TeV collected with the ATLAS detector at the LHC during 2011
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