1,308 research outputs found
LHC sensitivity to the decay of a Higgs boson to tau mu
We study the sensitivity of the LHC, with 20 inverse-fb of data, to lepton
flavour violating Higgs boson decays h -> tau+ mu- (and h -> tau+ e-). We
consider the large population of Higgses produced in gluon fusion, combined
with leptonic decays of the tau, and estimate that the LHC could set a 95 %
confidence level bound BR(h -> tau mu) < 4.5 \times 10^{-3}. This correponds to
a coupling of order the Cheng-Sher ansatz y_{tau mu} = sqrt{m_tau m_mu/v^2}.Comment: 6 pages, 4 figures, references adde
Of Contact Interactions and Colliders
The hierarchy of scales which would allow dimension-six contact interactions
to parametrise New Physics may not be verified at colliders. Instead, we
explore the feasability and usefulness of parametrising the high-energy tail of
distributions at the LHC using form factors. We focus on the process pp -> l+l-
in the presence of t (or s)-channel New Physics, guess a form factor from the
partonic cross-section, and attempt to use data to constrain its coefficients,
and the coefficients to constrain models. We find that our choice of form
factor decribes t-channel exchange better than a contact interaction, and the
coefficients in a particular model can be obtained from the partonic
cross-section. We estimate bounds on the coefficients by fitting the form
factors to available data. For the parametrisation corresponding to the contact
interaction approximation, our expected bounds on the scale are
within ~ 15% of the latest limits from the LHC experiments.Comment: 5 pages, 4 figure
Leptoquarks decaying to a top quark and a charged lepton at hadron colliders
We study the sensitivity of the Tevatron and the 7 TeV LHC to a leptoquark S
coupling to a top quark and a charged lepton L (= e, mu, or tau). For the
Tevatron, we focus on the case m_S < m_t, where the leptoquark pair production
cross section is large, and the decay is three-body: S --> W b L^{\pm}. We
argue that existing Tevatron observations could exclude m_S \lsim 160 GeV. For
m_S > m_t, we show that the LHC experiments with low integrated luminosity
could be sensitive to such leptoquarks decaying to tl^{\pm} with l= mu or tau.Comment: 13 pages, 6 figures, minor changes (typos
Collider Signature of T-quarks
Little Higgs models with T Parity contain new vector-like fermions, the T-odd
quarks or "T-quarks", which can be produced at hadron colliders with a
QCD-strength cross section. Events with two acoplanar jets and large missing
transverse energy provide a simple signature of T-quark production. We show
that searches for this signature with the Tevatron Run II data can probe a
significant part of the Little Higgs model parameter space not accessible to
previous experiments, exploring T-quark masses up to about 400 GeV. This reach
covers parts of the parameter space where the lightest T-odd particle can
account for the observed dark matter relic abundance. We also comment on the
prospects for this search at the Large Hadron Collider (LHC).Comment: 5 pages, 3 figure
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Collider signature of T-quarks
Little Higgs models with T Parity contain new vector-like fermions, the T-odd quarks or ''T-quarks'', which can be produced at hadron colliders with a QCD-strength cross section. Events with two acoplanar jets and large missing transverse energy provide a simple signature of T-quark production. We show that searches for this signature with the Tevatron Run II data can probe a significant part of the Little Higgs model parameter space not accessible to previous experiments, exploring T-quark masses up to about 400 GeV. This reach covers parts of the parameter space where the lightest T-odd particle can account for the observed dark matter relic abundance. We also comment on the prospects for this search at the Large Hadron Collider (LHC)
LHC sensitivity to lepton flavour violating Z boson decays
We estimate that the LHC could set bounds BR(Z -> mu^\pm e^\mp) < 4.1 *
10^{-7} and BR(Z -> tau^\pm mu^\mp)< 3.5 * 10^{-6} (at 95% C.L.) with 20
inverse fb of data at 8 TeV. A similar sensitivity can be anticipated for Z ->
tau^\pm e^\mp, because we consider leptonic tau decays such that Z -> tau^+
mu^- gives e^+ \mu^- +$ invisibles. These limits can be compared to the LEP1
bounds of order 10^{-5} to 10^{-6}. Such collider searches are sensitive to a
flavour-changing effective Z coupling which is energy dependent, so are
complementary to bounds obtained from tau to 3mu and mu to 3e.Comment: 11 pages, 2 figures, version for publicatio
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Combined CDF and D0 upper limits on MSSM Higgs boson production in tau-tau final states with up to 2.2 fb-1
Combined results are presented on the search for a neutral Higgs boson in the di-tau final state using 1.8 fb{sup -1} and 2.2 fb{sup -1} of integrated luminosity collected at the CDF and D0 experiments respectively. Data were collected in p{bar p} collisions at a centre of mass energy of 1.96 TeV during RunII of the Tevatron. Limits are set on the cross section x branching ratio ranging from 13.6 pb to 0.653 pb for Higgs masses from 90 GeV to 200 GeV respectively. The results are then interpreted as limits in four different benchmark scenarios within the framework of the MSSM
Efficacy of colistin alone and in various combinations for the treatment of experimental osteomyelitis due to carbapenemase-producing Klebsiella pneumoniae
Objectives: In a new experimental model of carbapenemase-producing Klebsiella pneumoniae osteomyelitis we evaluated the efficacy of colistin alone and in various combinations and examined the emergence of colistin-resistant strains and cross- resistance to host defence peptides (HDPs).Methods: KPC-99YC is a clinical strain with intermediate susceptibility to meropenem (MICâ=â4âmg/L) and full susceptibility to gentamicin, colistin and tigecycline (MICsâ=â1âmg/L) and fosfomycin (MICâ=â32âmg/L). Timeâkill curves were performed at 4Ă MIC. Osteomyelitis was induced in rabbits by tibial injection of 2âĂâ108âcfu. Treatment started 14âdays later for 7âdays in seven groups: (i) control; (ii) colistin; (iii) colistinâ+âgentamicin; (iv) colistinâ+âtigecycline; (v) colistinâ+âmeropenem; (vi) colistinâ+âmeropenemâ+âgentamicin; and (vii) colistinâ+â fosfomycin.Results: In vitro, colistin was rapidly bactericidal, but regrowth occurred after 9âh. Combinations of colistin with meropenem or fosfomycin were synergistic, whereas combination with tigecycline was antagonistic. In vivo, colistin alone was not effective. Combinations of colistin with meropenem or fosfomycin were bactericidal (Pâ <â0.001) and the addition of gentamicin enhanced the efficacy of colistinâ+âmeropenem (Pâ=â0.025). Tigecycline reduced the efficacy of colistin (Pâ=â0.007). Colistin-resistant strains emerged in all groups except colistinâ+âfosfomycin and two strains showed cross-resistance to HDP LL-37.Conclusions: In this model, combinations of colistin plus meropenem, with or without gentamicin, or colistin plus fosfomycin were the only effective therapies. The combination of colistin and tigecycline should be administered with caution, as it may be antagonistic in vitro and in vivo
Deciphering the Structure, Growth and Assembly of Amyloid-Like Fibrils Using High-Speed Atomic Force Microscopy
Formation of fibrillar structures of proteins that deposit into aggregates has been suggested to play a key role in various neurodegenerative diseases. However mechanisms and dynamics of fibrillization remains to be elucidated. We have previously established that lithostathine, a protein overexpressed in the pre-clinical stages of Alzheimer's disease and present in the pathognomonic lesions associated with this disease, form fibrillar aggregates after its N-terminal truncation. In this paper we visualized, using high-speed atomic force microscopy (HS-AFM), growth and assembly of lithostathine protofibrils under physiological conditions with a time resolution of one image/s. Real-time imaging highlighted a very high velocity of elongation. Formation of fibrils via protofibril lateral association and stacking was also monitored revealing a zipper-like mechanism of association. We also demonstrate that, like other amyloid Ă peptides, two lithostathine protofibrils can associate to form helical fibrils. Another striking finding is the propensity of the end of a growing protofibril or fibril to associate with the edge of a second fibril, forming false branching point. Taken together this study provides new clues about fibrillization mechanism of amyloid proteins
Measurement of the Tau Lepton Polarisation at LEP2
A first measurement of the average polarisation P_tau of tau leptons produced in e+e- annihilation at energies significantly above the Z resonance is presented. The polarisation is determined from the kinematic spectra of tau hadronic decays. The measured value P_tau = -0.164 +/- 0.125 is consistent with the Standard Model prediction for the mean LEP energy of 197 GeV.A first measurement of the average polarisation PÏ of tau leptons produced in e + e â annihilation at energies significantly above the Z resonance is presented. The polarisation is determined from the kinematic spectra of tau hadronic decays. The measured value PÏ=â0.164±0.125 is consistent with the Standard Model prediction for the mean LEP energy of 197 GeV.A first measurement of the average polarisation P_tau of tau leptons produced in e+e- annihilation at energies significantly above the Z resonance is presented. The polarisation is determined from the kinematic spectra of tau hadronic decays. The measured value P_tau = -0.164 +/- 0.125 is consistent with the Standard Model prediction for the mean LEP energy of 197 GeV
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