2,498 research outputs found
Higgs friends and counterfeits at hadron colliders
We consider the possibility of "Higgs counterfeits" - scalars that can be
produced with cross sections comparable to the SM Higgs, and which decay with
identical relative observable branching ratios, but which are nonetheless not
responsible for electroweak symmetry breaking. We also consider a related
scenario involving "Higgs friends," fields similarly produced through gg fusion
processes, which would be discovered through diboson channels WW, ZZ, gamma
gamma, or even gamma Z, potentially with larger cross sections times branching
ratios than for the Higgs. The discovery of either a Higgs friend or a Higgs
counterfeit, rather than directly pointing towards the origin of the weak
scale, would indicate the presence of new colored fields necessary for the
sizable production cross section (and possibly new colorless but electroweakly
charged states as well, in the case of the diboson decays of a Higgs friend).
These particles could easily be confused for an ordinary Higgs, perhaps with an
additional generation to explain the different cross section, and we emphasize
the importance of vector boson fusion as a channel to distinguish a Higgs
counterfeit from a true Higgs. Such fields would naturally be expected in
scenarios with "effective Z's," where heavy states charged under the SM produce
effective charges for SM fields under a new gauge force. We discuss the
prospects for discovery of Higgs counterfeits, Higgs friends, and associated
charged fields at the LHC.Comment: 27 pages, 5 figures. References added and typos fixe
The Efficacy of Sequential Biologic Agents in Refractory Rheumatoid Arthritis After Failure of Initial DMARD and Anti-Tumor Necrosis Factor Therapy
Introduction/Objective: The efficacy of biologic therapy in the treatment of rheumatoid arthritis (RA) has been well-established but, in practice, a quarter of patients will either not respond to the first biologic agent or will suffer an adverse event requiring a switch to a different drug. While clinical guidelines exist to help guide therapy and previous studies have examined sequential use of anti-TNF agents, there is little data to inform a multiple switch strategy. Our aim was to measure the efficacy of multiple switches of biologic in severe refractory RA. Methods: We enrolled 111 patients whose therapy with one anti-TNF agent had failed in this open-label observational study. These patients were all treated with a second biologic agent and 27 ultimately required treatment with a third. The response to the therapy and disease activity were assessed at 6 and 12 months after each switch. Results: The remission rates at 6 months were lower than previously reported and the initiation of a second biologic agent resulted in significant improvement at 12 months, including DAS remission in 36% of patients. The response in those receiving a third biologic was less pronounced, as might be expected in this relatively treatment-refractory population. In this group, only patients treated with tocilizumab had maintained remission at one year. Conclusion: Patients who do not respond to an anti-TNF agent often benefit from being switched to a second, or even third, biologic. Importantly, it may take longer than expected to fully assess the effectiveness of a second or third agent in patients with refractory disease
A Collective Breaking of R-Parity
Supersymmetric theories with an R-parity generally yield a striking missing
energy signature, with cascade decays concluding in a neutralino that escapes
the detector. In theories where R-parity is broken the missing energy is
replaced with additional jets or leptons, often making traditional search
strategies ineffective. Such R-parity violation is very constrained, however,
by resulting B and L violating signals, requiring couplings so small that LSPs
will decay outside the detector in all but a few scenarios. In theories with
additional matter fields, R-parity can be broken collectively, such that
R-parity is not broken by any single coupling, but only by an ensemble of
couplings. Cascade decays can proceed normally, with each step only sensitive
to one or two couplings at a time, but B and L violation requires the full set,
yielding a highly suppressed constraint. s-channel production of new scalar
states, typically small for standard RPV, can be large when RPV is broken
collectively. While missing energy is absent, making these models difficult to
discover by traditional SUSY searches, they produce complicated many object
resonances (MORes), with many different possible numbers of jets and leptons.
We outline a simple model and discuss its discoverability at the LHC.Comment: 28 pages, 10 figure
Neurospora from natural populations: Population genomics insights into the Life history of a model microbial Eukaryote
The ascomycete filamentous fungus Neurospora crassa played a historic role in experimental biology and became a model system for genetic research. Stimulated by a systematic effort to collect wild strains initiated by Stanford geneticist David Perkins, the genus Neurospora has also become a basic model for the study of evolutionary processes, speciation, and population biology. In this chapter, we will first trace the history that brought Neurospora into the era of population genomics. We will then cover the major contributions of population genomic investigations using Neurospora to our understanding of microbial biogeography and speciation, and review recent work using population genomics and genome-wide association mapping that illustrates the unique potential of Neurospora as a model for identifying the genetic basis of (potentially adaptive) phenotypes in filamentous fungi. The advent of population genomics has contributed to firmly establish Neurospora as a complete model system and we hope our review will entice biologists to include Neurospora in their research
Search for time-dependent B0s - B0s-bar oscillations using a vertex charge dipole technique
We report a search for B0s - B0s-bar oscillations using a sample of 400,000
hadronic Z0 decays collected by the SLD experiment. The analysis takes
advantage of the electron beam polarization as well as information from the
hemisphere opposite that of the reconstructed B decay to tag the B production
flavor. The excellent resolution provided by the pixel CCD vertex detector is
exploited to cleanly reconstruct both B and cascade D decay vertices, and tag
the B decay flavor from the charge difference between them. We exclude the
following values of the B0s - B0s-bar oscillation frequency: Delta m_s < 4.9
ps-1 and 7.9 < Delta m_s < 10.3 ps-1 at the 95% confidence level.Comment: 18 pages, 3 figures, replaced by version accepted for publication in
Phys.Rev.D; results differ slightly from first versio
Critical Exponents, Hyperscaling and Universal Amplitude Ratios for Two- and Three-Dimensional Self-Avoiding Walks
We make a high-precision Monte Carlo study of two- and three-dimensional
self-avoiding walks (SAWs) of length up to 80000 steps, using the pivot
algorithm and the Karp-Luby algorithm. We study the critical exponents
and as well as several universal amplitude ratios; in
particular, we make an extremely sensitive test of the hyperscaling relation
. In two dimensions, we confirm the predicted
exponent and the hyperscaling relation; we estimate the universal
ratios , and (68\% confidence
limits). In three dimensions, we estimate with a
correction-to-scaling exponent (subjective 68\%
confidence limits). This value for agrees excellently with the
field-theoretic renormalization-group prediction, but there is some discrepancy
for . Earlier Monte Carlo estimates of , which were , are now seen to be biased by corrections to scaling. We estimate the
universal ratios and ; since , hyperscaling holds. The approach to
is from above, contrary to the prediction of the two-parameter
renormalization-group theory. We critically reexamine this theory, and explain
where the error lies.Comment: 87 pages including 12 figures, 1029558 bytes Postscript
(NYU-TH-94/09/01
Blood pressure and site-specific cancer mortality: evidence from the original Whitehall study
Studies relating blood pressure to cancer risk have some shortcomings and have revealed inconsistent findings. In 17498 middle-aged London-based government employees we related systolic and diastolic blood pressure recorded at baseline examination (1967-1970) to the risk of cancer mortality risk at 13 anatomical sites 25 years later. Following adjustment for potential confounding and mediating factors, inverse associations between blood pressure and mortality due to leukaemia and cancer of the pancreas (diastolic only) were seen. Blood pressure was also positively related to cancer of the liver and rectum (diastolic only). The statistically significant blood pressure-cancer associations seen in this large-scale prospective investigation offering high power were scarce and of sufficiently small magnitude as to be attributable to chance or confounding
hEGR1 is induced by EGF, inhibited by gefitinib in bladder cell lines and related to EGF receptor levels in bladder tumours
The effect of EGF and gefitinib on two EGFR-positive human bladder cancer cell lines has been investigated using array-based gene expression profiling. The most prominent transcript, increased up to 6.7-fold by EGF compared with controls in RT112 cells, was human early growth response protein 1 (hEGR1). This induction was prevented by gefitinib. The hEGR1 mRNA in EGF-treated samples was reduced in the presence of gefitinib, as was hEGR1 protein in cell lysates. In the RT4 cells, hEGR1 expression was halved in the presence of EGF and gefitinib in combination. In bladder tumour samples, there was a significant correlation between hEGR1 mRNA detected by RT-PCR and EGFR detected by ligand binding, (P=0.042). The induction by EGF of the hEGR1 gene, mRNA and protein in RT112 cells, and its inhibition by gefitinib, together with the detection of hEGR1 mRNA in bladder tumours, suggests that hEGR1 may be important in the EGFR growth-signalling pathway in bladder cancer and should be further investigated for its prognostic significance and as a potential therapeutic target
Measurement of the running of the QED coupling in small-angle Bhabha scattering at LEP
Using the OPAL detector at LEP, the running of the effective QED coupling
alpha(t) is measured for space-like momentum transfer from the angular
distribution of small-angle Bhabha scattering. In an almost ideal QED
framework, with very favourable experimental conditions, we obtain:
Delta alpha(-6.07GeV^2) - Delta alpha(-1.81GeV^2) = (440 pm 58 pm 43 pm 30) X
10^-5, where the first error is statistical, the second is the experimental
systematic and the third is the theoretical uncertainty. This agrees with
current evaluations of alpha(t).The null hypothesis that alpha remains constant
within the above interval of -t is excluded with a significance above 5sigma.
Similarly, our results are inconsistent at the level of 3sigma with the
hypothesis that only leptonic loops contribute to the running. This is
currently the most significant direct measurment where the running alpha(t) is
probed differentially within the measured t range.Comment: 43 pages, 12 figures, Submitted to Euro. Phys. J.
A Measurement of Rb using a Double Tagging Method
The fraction of Z to bbbar events in hadronic Z decays has been measured by
the OPAL experiment using the data collected at LEP between 1992 and 1995. The
Z to bbbar decays were tagged using displaced secondary vertices, and high
momentum electrons and muons. Systematic uncertainties were reduced by
measuring the b-tagging efficiency using a double tagging technique. Efficiency
correlations between opposite hemispheres of an event are small, and are well
understood through comparisons between real and simulated data samples. A value
of Rb = 0.2178 +- 0.0011 +- 0.0013 was obtained, where the first error is
statistical and the second systematic. The uncertainty on Rc, the fraction of Z
to ccbar events in hadronic Z decays, is not included in the errors. The
dependence on Rc is Delta(Rb)/Rb = -0.056*Delta(Rc)/Rc where Delta(Rc) is the
deviation of Rc from the value 0.172 predicted by the Standard Model. The
result for Rb agrees with the value of 0.2155 +- 0.0003 predicted by the
Standard Model.Comment: 42 pages, LaTeX, 14 eps figures included, submitted to European
Physical Journal
- …