Search

This search for magnetic monopoles (MMs) and high electric charge objects (HECOs) with spins 0, 1/2, and 1, uses for the first time the full MoEDAL detector, exposed to 6.46  fb^{-1} proton-proton collisions at 13 TeV. The results are interpreted in terms of Drell-Yan and photon-fusion pair production. Mass limits on direct production of MMs of up to 10 Dirac magnetic charges and HECOs with electric charge in the range 10e to 400e, were achieved. The charge limits placed on MM and HECO production are currently the strongest in the world. MoEDAL is the only LHC experiment capable of being directly calibrated for highly ionizing particles using heavy ions and with a detector system dedicated to definitively measuring magnetic charge.

We report on a search for magnetic monopoles (MMs) produced in ultraperipheral Pb-Pb collisions during Run 1 of the LHC. The beam pipe surrounding the interaction region of the CMS experiment was exposed to 184.07  μb^{-1} of Pb-Pb collisions at 2.76 TeV center-of-mass energy per collision in December 2011, before being removed in 2013. It was scanned by the MoEDAL experiment using a SQUID magnetometer to search for trapped MMs. No MM signal was observed. The two distinctive features of this search are the use of a trapping volume very close to the collision point and ultrahigh magnetic fields generated during the heavy-ion run that could produce MMs via the Schwinger effect. These two advantages allowed setting the first reliable, world-leading mass limits on MMs with high magnetic charge. In particular, the established limits are the strongest available in the range between 2 and 45 Dirac units, excluding MMs with masses of up to 80 GeV at a 95% confidence level.

Electrically charged particles can be created by the decay of strong enough electric fields, a phenomenon known as the Schwinger mechanism 1 . By electromagnetic duality, a sufficiently strong magnetic field would similarly produce magnetic monopoles, if they exist 2 . Magnetic monopoles are hypothetical fundamental particles that are predicted by several theories beyond the standard model 3-7 but have never been experimentally detected. Searching for the existence of magnetic monopoles via the Schwinger mechanism has not yet been attempted, but it is advantageous, owing to the possibility of calculating its rate through semi-classical techniques without perturbation theory, as well as that the production of the magnetic monopoles should be enhanced by their finite size 8,9 and strong coupling to photons 2,10 . Here we present a search for magnetic monopole production by the Schwinger mechanism in Pb-Pb heavy ion collisions at the Large Hadron Collider, producing the strongest known magnetic fields in the current Universe 11 . It was conducted by the MoEDAL experiment, whose trapping detectors were exposed to 0.235 per nanobarn, or approximately 1.8 × 10 9 , of Pb-Pb collisions with 5.02-teraelectronvolt center-of-mass energy per collision in November 2018. A superconducting quantum interference device (SQUID) magnetometer scanned the trapping detectors of MoEDAL for the presence of magnetic charge, which would induce a persistent current in the SQUID. Magnetic monopoles with integer Dirac charges of 1, 2 and 3 and masses up to 75 gigaelectronvolts per speed of light squared were excluded by the analysis at the 95% confidence level. This provides a lower mass limit for finite-size magnetic monopoles from a collider search and greatly extends previous mass bounds., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

The MoEDAL trapping detector consists of approximately 800 kg of aluminum volumes. It was exposed during run 2 of the LHC program to 6.46  fb^{-1} of 13 TeV proton-proton collisions at the LHCb interaction point. Evidence for dyons (particles with electric and magnetic charge) captured in the trapping detector was sought by passing the aluminum volumes comprising the detector through a superconducting quantum interference device (SQUID) magnetometer. The presence of a trapped dyon would be signaled by a persistent current induced in the SQUID magnetometer. On the basis of a Drell-Yan production model, we exclude dyons with a magnetic charge ranging up to five Dirac charges (5g_{D}) and an electric charge up to 200 times the fundamental electric charge for mass limits in the range 870-3120 GeV and also monopoles with magnetic charge up to and including 5g_{D} with mass limits in the range 870-2040 GeV.

MoEDAL is designed to identify new physics in the form of stable or pseudostable highly ionizing particles produced in high-energy Large Hadron Collider (LHC) collisions. Here we update our previous search for magnetic monopoles in Run 2 using the full trapping detector with almost four times more material and almost twice more integrated luminosity. For the first time at the LHC, the data were interpreted in terms of photon-fusion monopole direct production in addition to the Drell-Yan-like mechanism. The MoEDAL trapping detector, consisting of 794 kg of aluminum samples installed in the forward and lateral regions, was exposed to 4.0  fb^{-1} of 13 TeV proton-proton collisions at the LHCb interaction point and analyzed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges equal to or above the Dirac charge are excluded in all samples. Monopole spins 0, ½, and 1 are considered and both velocity-independent and-dependent couplings are assumed. This search provides the best current laboratory constraints for monopoles with magnetic charges ranging from two to five times the Dirac charge.

It is well known that certain special classes of self-gravitating point-like defects, such as global (non gauged) monopoles, give rise to non-asymptotically flat space-times characterized by solid angle deficits, whose size depends on the details of the underlying microscopic models. The scattering of electrically neutral particles on such space-times is described by amplitudes that exhibit resonant behaviour when thescattering and deficit angles coincide. This, in turn, leads to ring-like structures where the cross sections are formally divergent ("singular lensing"). In this work, we revisit this particular phenomenon, with the twofold purpose of placing it in a contemporary and more general context, in view of renewed interest in the theory and general phenomenology of such defects, and, more importantly, of addressing certain subtleties that appear in the particular computation that leads to the aforementioned effect. In particular, by adopting a specific regularization procedure for the formally infinite Legendre series encountered, we manage to ensure the recovery of the Minkowski space-time, and thus the disappearance of the lensing phenomenon, in the no-defect limit, and the validity of the optical theorem for the elastic total cross section. In addition, the singular nature of the phenomenon is confirmed by means of an alternative calculation, which, unlike the original approach, makes no use of the generating function of the Legendre polynomials, but rather exploits the asymptotic properties of the Fresnel integrals.

We discuss modifications to the concept of an "antiparticle," induced by a breakdown of the CPT symmetry at a fundamental level, realized within an extended class of quantum gravity models. The resulting loss of particle-antiparticle identity in the neutral-meson system induces a breaking of the Einstein-Podolsky-Rosen correlation imposed by Bose statistics. This is parametrized by a complex parameter associated with the contamination by the "wrong symmetry" state. The physical consequences are studied, and novel observables of CPT violation in phi factories are proposed.

It is shown that the probe-independent charge radius of the neutrino is a physical observable; as such, it may be extracted from experiment, at least in principle. This is accomplished by expressing a set of experimental nu(mu)-e cross sections in terms of the finite charge radius and two additional gauge- and renormalization-group-invariant quantities, corresponding to the electroweak effective charge and mixing angle.

It is shown that the fundamental properties of gauge independence, gauge invariance, unitarity, and analyticity of the S matrix lead to the unambiguous generalization of the pinch technique algorithm to two loops.

The adherence of strains of Candida albicans to buccal epithelial cells as well as the phagocytosis of these organisms by human polymorphonuclear leucocytes (PMNL) was studied. The strains of C. albicans were obtained from patients' urine. from bird faeces and from soil. The strains of C. albicans obtained from patients and the environment displayed greater adhering ability (23.8 +/- 6.4 and 27.5 +/- 5.2 respectively) than the avian strains (14.4 +/- 2.2) (P < 0.01). Strains obtained from the environment were resistant to phagocytosis (81.6 +/- 0.2 organisms ingested per 200 PMNL) and killing (8.4 +/- 2.6%) by PMNL as compared to human and avian strains (P < 0.01). These observations indicate that environmental strains of C. albicans may be more virulent for human beings.

Patients with malignancies are at high risk to develop infections by Candida albicans. We have compared the adherence of C. albicans isolated from urine cultures to bladder epithelial cells obtained from healthy volunteers and patients with cancer of the bladder. The mean number of C. albicans adhering per epithelial cell from areas infiltrated from cancer was significantly higher as compared to cells obtained from intact areas of cancerous bladders and from normal bladders. The increased adherence of C. albicans to cancerous epithelial cells suggests that malignancies are associated with alterations of the epithelial cell surface which render the cells more susceptible to colonization by C. albicans. The increased colonization may predispose these patients to C. albicans infections.

We tested peripheral blood from 60 patients with definite multiple sclerosis (MS) and 60 healthy controls for polymorphonuclear leukocyte (PMNL) functions and found significant disorders in adherence (9.07% +/- 8.18% for patients versus 28.97% +/- 5.76% for controls), chemotaxis (18.32 +/- 3.1 for patients versus 30.49 +/- 4.52 for controls), phagocytosis (73.6 +/- 25.25 for patients versus 111.2 +/- 25.7 for controls), and bactericidal action (10.35% +/- 5% for patients versus 25.09% +/- 4.82% for controls). All differences were significant (p < 0.001). We confirmed the results by retesting 3 to 8 months later. The depressed PMNL functions in MS patients may explain their increased susceptibility to infections of the respiratory, digestive, and urinary tracts.

Ciprofloxacin was administered to 10 healthy volunteers at a dose of 250 mg orally. Serum and polymorphonuclear leukocytes (PMNLs) were obtained from all subjects before the administration of the drug and 12 hours after the administration. In addition serum was obtained from all subjects at 24 and 48 hours after ciprofloxacin administration. All sera and PMNLs were used for the chemotactic, phagocytic and killing determinations of the PMNLs. The results demonstrated that serum obtained 12 hours after the administration of ciprofloxacin potentiates PMNL chemotactic activity (chemotactic index (CI) = 33.0 +/- 4.2 microns (means +/- S.D.)) as compared to the chemotactic activity generated by serum obtained prior to administration of the drug, CI = 20.4 +/- 4.4 microns (p < 0.01). Serum obtained 24 and 48 hours after ciprofloxacin administration did not stimulate PMNL function. The administration of ciprofloxacin did not have any direct influence on the PMNLs in terms of their chemotactic response. Furthermore, serum obtained after the administration of ciprofloxacin markedly enhanced PMNL phagocytosis and killing of all organisms tested. Ciprofloxacin also acted directly on the PMNLs and increased their bactericidal activity. These results demonstrate that ciprofloxacin potentiates PMNL function in vivo which may be of potential clinical benefit.

The antimicrobial efficacy of preservatives in ophthalmic solutions was tested. Five strains were used as challenge organisms. They represented bacteria, yeasts and molds. Sixty per cent of the ophthalmic solutions showed a good preservation against S. aureus ATCC 6538, according to the standards and in 40% of cases, the bacteria disappeared on the second week. Against E. coli ATCC 8739, 90% of the samples were well preserved and in 10% the bacteria disappeared by the second week. Against Ps. aeruginosa ATCC 9027, C. Albicans ATCC 10231 and Asp. niger ATCC 16404, the ophthalmic solutions showed a 100% preservation. The majority of the products showed a satisfactory preservation. They contained declared preservatives and sometimes combinations of two antimicrobial agents.

All strains of oral streptococci tested and specially those of Streptococcus mutans, Strep. sanguis and Strep. mitior produced more than one distinct bacteriocin-like substance with variable inhibitory activity on 20 indicator staphylococci. Inhibitory activity was comparatively higher on nasal strains of Staph. aureus and Staph. epidermidis than on strains of both species isolated from the mouth. Nineteen of 20 staphylococcal indicators were inhibited by 1-12 of the 12 effector streptococci. Sensitivity of nasal staphylococci to bacteriocins (frequency of positive inhibitory tests and total inhibition zone diameters) was significantly higher (P less than 0.001, chi 2 test and P less than 0.05, t test respectively) than that of oral ones. The sensitivity of nasal over oral Staph. aureus (P less than 0.001 and P less than 0.01) and of oral Staph. epidermidis over oral Staph. aureus (P less than 0.01 and P less than 0.05) was also significantly higher. The evaluation of variability of inhibitory patterns of bacteriocins produced by streptococci (p-typing), of sensitivity patterns of staphylococci to bacteriocins (s-typing) and of the significantly higher sensitivity of nasal over oral staphylococci to bacteriocins from the epidemiological and ecological viewpoints are discussed.

The survival of bacteriophage 1 of the Salmonella typhimurium phage typing scheme was studied in four different types of sterile soil at 4.20 and 37 degrees C. The longevity of the phage was generally short, not exceeding 36 days and depended on the temperature and the type of soil.

Culturing Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae in the presence of subinhibitory concentrations (1/4 MIC) of trimethoprim, sulphamethoxazole or their combination, resulted in reduced adherence of all the above strains. The number of phagocytosed bacteria pre-exposed to subinhibitory concentrations of the above antibiotics was not significantly changed, but a significant increase of bactericidal activity of the polymorphonuclear leucocytes was observed. Furthermore, filtrates of K. pneumoniae and P. mirabilis grown in the presence of trimethoprim alone or in combination with sulphamethoxazole induced an increased chemotactic response of human polymorphonuclear leucocytes.

The in vitro antibacterial activity of HR-756 compared to cefoxitin and cefuroxime. 122 multiresistant clinical isolates including Enterobacteriaceae (104) and P. aeruginosa (18), which present particular problems in antibiotic chemotherapy, were selected for study. HR-756 inhibited all the stains of S. marcescens, P. mirabilis and indole-positive Proteus spp. at a concentration of 1,3 and 12 micrograms/ml, respectively; beta-lactamase-producing strains were also susceptible. 90% of K. pneumoniae and more than half of the Enterobacter and P. aeruginosa were inhibited from the drug at a concentration 16 microgram/ml. Cefoxitin and cefuroxime were less active than HR-756. Cefoxitin was more effective against S. marcescens and P. mirabilis while the same was the case with cefuroxime against K. pneumoniae strains. The greater efficiency of HR-756 over cefoxitin and cefuroxime against these multiply resistant isolates seems to be due not only to its indifference to the beta-lactamases but also to its easier penetrability into the bacterial cell.

The survival of Bacteriophage 1, of the Salmonella typhimurium phage typing scheme, was studied in nutrient broth, saline and distilled water at 4 degrees C, 20 degrees C and 37 degrees C. From the results of this work it can be concluded that the survival of the phage is longer at 4 degrees C in all three maintenance media and that the survival is longer in both nutrient broth and saline than in distilled water.

Clinical isolates of Escherichia coli sensitive and resistant to penicillin were compared in lipid composition and 14C-labelled penicillin uptake, as possible factors in resistance. Except for a slight increase in the triglyceride fraction in sensitive strains there were no qualitative or quantitative differences in the classes of extractable lipids present. Gas-liquid chromatography of the phospholipid and triglyceride fatty acids of the polar and non-polar fatty acids of the bound lipids showed that the same kinds of fatty acids were present. There was an increase of myristate in the chloroform-methanol extractable lipids of highly resistant strains accompanied by a rather general decrease of other fatty acids. Gas-chromatographic analysis of the polar-bound lipids showed an increase of the beta-hydroxydecanoic acid in the resistant strains. By studying the uptake of 14C-labelled benzylpenicillin and the crypticity of the beta-lactamase, evidence has been produced that a decreased permeability of resistant strains to penicillin cooperates with beta-lactamase to induce a high level of resistance. The altered lipid metabolism may reflect the special architectural changes in the cell wall which cause decreased permeability.

Ninety-eight hospital strains of Pseudomonas aeruginosa isolated from six different hospitals in Athens were serotyped by a slide agglutination test with unabsorbed commercial antisera. Serotypes O6, O11, O12, and "pool E" strains (strains that agglutinated only in pool E, which contained antisera against O2, O5, O15, and O16 antigens, but did not agglutinate in the individual antisera) predominated, accounting for more than 62% of all isolates tested. In respect to serotypes, (i) there was no apparent correlation with hospital of origin, (ii) most strains of serotypes O6 and O11 were sensitive to gentamicin and carbenicillin (iii) most strains of pool E were from urine and were resistant to these drugs, (iv) all 9 strains of serotype O12 tested were resistant to carbenicillin and all 5 strains tested hydrolyzed this drug, and (v) 24 of 25 strains of pool E were resistant to carbenicillin but only 2 of 17 strains hydrolyzed it.

A medium containing heart infusion agar supplemented with bile salts, lithium chloride, sodium thiosulfate, and sodium citrate was developed for the selective growth of Proteus.

Host defense mechanisms in transfusion-dependent non-splenectomized patients with beta-thalassemia were studied. Polymorphonuclear leukocytes (PMNLs) of non-splenectomized patients responded poorly to zymosan generated chemotactic factors. Chemotactic indices were 22.1 microns +/- 2.8 (mean +/- S.D.) using zymosan activated serum (ZAS) as the attractant in comparison to 20.4 microns +/- 2.6 when fresh untreated serum was used. In contrast, chemotactic indices of normal PMNLs increased from 21.1 microns to 33.6 microns +/- 3.1 in response to ZAS. Normal PMNL responses to a mixture of normal ZAS and thalassemic serum were inhibited; the mean chemotactic index was 18.1 microns +/- 5.1 with use of ZAS alone. Splenectomy temporarily reverses these alterations. Adherence to nylon wool of PMNLs suspended in fresh thalassemic serum prior to splenectomy was 3.1% +/- 1.1 (mean +/- S.D.); 20 days after splenectomy adherence increased to 14.0% +/- 2.8 (P = 0.0001) and remained at this level for 90 days. At 120 and 150 days after splenectomy adherence decreased to 1.5% +/- 0.8 and 1.0% +/- 0.85 respectively. Splenectomy also transiently abrogated the failure of zymosan to generate chemotactic factors in thalassemic serum.

The antibacterial activity of gentamicin and sisomicin was studied in 148 recent clinical isolates of Proteus obtained from patients hospitalized in Athens. Both gentamicin and sisomicin were found to be active with sisomicin generally being the more active of the two; P. mirabilis strains were less susceptible than the indole-positive strains, but P. mirabilis organisms isolated from the respiratory tract were more sensitive to sisomicin than those isolated from the urine. Susceptibility testing with the two aminoglycoside antibiotics was affected by inoculum size and by the test broth used. Sisomicin sensitivity testing with the disc-agar diffusion method and broth dilution method was reliable for the indole-positive strains of Proteus but did not separate all sensitive from resistant strains of P. mirabilis. An in vitro synergism was demonstrated between sisomicin and the semisynthetic penicillin, ticarcillin.

Netilmicin was compared with sisomicin, tobramycin and amikacin against 65 recent clinical enterobacterial isolates found to be highly resistant to gentamicin (MIC larger than or equal to 80 microgram/ml). Netilmicin showed a high activity against 20 out of 65 strains tested. Most of the sensitive strains (60%) to netilmicin required a concentration of gentamicin equal or lower than 160 microgram/ml for inhibition. Amikacin proved to be extremely effective in all the organisms tested. Tobramycin was consistently less active than either netilmicin or amikacin and the same was the case with sisomicin. The MIC was determined in both solid and liquid media for 24 strains. Depending upon which aminoglycoside was used, we found that 10-30% of the enterobacteriaceae exhibited a twofold diminution of MIC when tested in broth as compared to agar, while the greater proportion of strains was characterized by a higher MIC tested in broth as compared to agar.

Twenty disinfectants were tested against a strain of K. pneumoniae. A suspension test with incremental addition of microorganisms was used. The influence of interfering substances (proteins and hard water) on the activity of disinfectants was also determined. Iodine compounds were influenced by proteins in distilled and hard water. The presence of mineral ions inactivated the polyvinylpyrrolidone-iodine 10% and chloroxylenol preparations against K. pneumoniae. The activity of some iodine products disappeared at the second and third incremental addition of microorganisms; the chloroxylenol and the phenolic compounds were inactivated by proteins at the third incremental addition. The sensibility of K. pneumoniae to the other disinfectants was not influenced by proteins, ions and incremental bacterial additions.