4,041 research outputs found
Universal Relations in Composite Higgs Models
We initiate a phenomenological study of `universal relations' in composite
Higgs models, which are dictated by nonlinear shift symmetries acting on the
125 GeV Higgs boson. These are relations among one Higgs couplings with two
electroweak gauge bosons (HVV), two Higgses couplings with two electroweak
gauge bosons (HHVV), one Higgs couplings with three electroweak gauge bosons
(HVVV), as well as triple gauge boson couplings (TGC), which are all controlled
by a single input parameter: the decay constant of the
pseudo-Nambu-Goldstone Higgs boson. Assuming custodial invariance in strong
sector, the relation is independent of the symmetry breaking pattern in the UV,
for an arbitrary symmetric coset . The complete list of corrections to
HVV, HHVV, HVVV and TGC couplings in composite Higgs models is presented to all
orders in , and up to four-derivative level, without referring to a
particular . We then present several examples of universal relations in
ratios of coefficients which could be extracted experimentally. Measuring the
universal relation requires a precision sensitive to effects of dimension-8
operators in the effective Lagrangian and highlights the importance of
verifying the tensor structure of HHVV interactions in the standard model,
which remains untested to date.Comment: 31 pages, 6 figure
Universal Imprints of a Pseudo-Nambu-Goldstone Higgs Boson
A large class of models addressing the electroweak naturalness problem
postulates the existence of new spontaneously broken global symmetries above
the weak scale. The Higgs boson arises as a pseudo-Nambu-Goldstone boson (pNGB)
whose interactions are nonlinear due to the presence of de- generate vacua. We
argue that, once the normalization of the pNGB decay constant f is determined,
the Higgs nonlinear interactions in the gauge sector are universal in the
infrared and independent of the symmetry breaking pattern G/H, even after
integrating out heavy composite resonances. We propose a set of "universal
relations" in Higgs couplings with electroweak gauge bosons and in triple gauge
boson couplings, which are unique predictions of the universal nonlinearity.
Experimental measurements of these relations would serve as the litmus test of
a pNGB Higgs boson.Comment: 5 page
Additive Effects of Heating and Exercise on Baroreflex Control of Heart Rate in Healthy Males
This study assessed the additive effects of passive heating and exercise on cardiac baroreflex sensitivity (cBRS) and heart rate variability (HRV). Twelve healthy young men (25±1 yrs, 23.8±0.5 kg/m229 ) randomly underwent two experimental sessions: heat stress (HS; whole-body heat stress using a tube-lined suit to increase core temperature by ~1°C) and normothermia (NT). Each session was composed of a: pre-intervention rest (REST1); HS or NT interventions; post-intervention rest (REST2); and 14 min of cycling exercise [7 min at 40%HRreserve (EX1) and 7 min at 60%HRreserve (EX2)]. Heart rate and finger blood pressure were continuously recorded. cBRS was assessed using the sequence (cBRSSEQ) and transfer function (cBRSTF) methods. HRV was assessed using the indices SDNN (standard deviation of RR intervals) and RMSSD (root mean square of successive RR intervals). cBRS and HRV were not different between sessions during EX1 and EX2 (i.e. matched heart rate conditions: EX1=116±3 vs. 114±3, EX2=143±4 vs. 142±3 bpm; but different workloads: EX1=50±9 vs. 114±8, EX2=106±10 vs. 165±8 Watts; for HS and NT, respectively; P<0.01). However, when comparing EX1 of NT with EX2 of HS (i.e. matched workload conditions, but with different heart rates), cBRS and HRV were significantly reduced in HS (cBRSSEQ = 1.6±0.3 vs. 0.6±0.1 ms/mmHg, P<0.01; SDNN = 2.3±0.1 vs. 1.3±0.2 ms, P<0.01). In conclusion, in conditions matched by HR, the addition of heat stress to exercise does not affect cBRS and HRV. Alternatively, in workload-matched conditions, the addition of heat to exercise results in reduced cBRS and HRV compared to exercise in normothermia
2,6-Diiodo-4-nitrophenol, 2,6-diiodo-4-nitrophenyl acetate and 2,6-diiodo-4-nitroanisole: interplay of hydrogen bonds, iodo-nitro interactions and aromatic [pi]-[pi]-stacking interactions to give supramolecular structures in one, two and three dimensions
Peer reviewedPublisher PD
A golden probe of nonlinear Higgs dynamics
The most salient generic feature of a composite
Higgs boson resides in the nonlinearity of its dynamics,
which arises from degenerate vacua associated with
the pseudo-Nambu–Goldstone (PNGB) nature of the Higgs
boson. It has been shown that the nonlinear Higgs dynamics
is universal in the IR and controlled only by a single parameter
f , the decay constant of the PNGB Higgs. In this work
we perform a fit, for the first time, to Wilson coefficients
of O(p4) operators in the nonlinear Lagrangian using the
golden H→4L decay channel. By utilizing both the “rate”
information in the signal strength and the “shape” information
in the fully differential spectra, we provide limits on the
Goldstone decay constant f , as well as O(p4) Wilson coefficients,
using Run 2 data at the LHC. In rate measurements
alone, the golden channel prefers a negative ξ = v2/ f 2 corresponding
to a non-compact coset structure. Including the
shape information, we identify regions of parameter space
where current LHC constraint on f is still weak, allowing
for ξ 0.5 or ξ −0.5. We also comment on future sensitivity
at the high-luminosity upgrade of the LHCwhich could
allow for simultaneous fits to multiple Wilson coefficients.United States Department of Energy (DOE)
DE-AC02-06CH11357
DE-SC0010143MINECO (ERDF)
FPA 2016-78220-C3-1-P
FPA 2013-47836-C3-2/3-PJuan de la Cierva programJunta de Andalucía
FQM-10
Cutaneous vascular responses to hypercapnia during whole-body heating
This article has been made available through the Brunel Open Access Publishing Fund and is available from the specified link - Copyright © 2008 Aerospace Medical Association (AsMA).Introduction:
Hypercapnia may be encountered in lung disease as well as during situations involving rebreathing of previously expired air (e.g., occupational diving). Inhibitory effects of elevated arterial carbon dioxide partial pressure on the central nervous system may result in impaired thermoregulation. This study tested the hypothesis that in heat-stressed subjects, cutaneous vascular responsiveness [expressed as cutaneous vascular conductance (CVC)] would be reduced during hypercapnic exposure.
Methods:
Four men and three women (mean ± SD; age: 35 ± 7 yr) rested supine while wearing a tube-lined suit perfused with 34°C water (normothermia). Following normothermic data collection, 50°C water was perfused through the suit to increase internal temperature approximately 1°C (whole-body heating). In both thermal conditions, a normoxic-hypercapnic (5% CO2, 21% O2, balance N2) gas mixture was inspired while forearm skin blood flux (laser-Doppler flow-metry) was measured continuously and was used for calculation of CVC (skin blood flux/mean arterial pressure).
Results:
End-tidal CO2 increased similarly throughout hypercapnic exposure during both normothermic and whole-body heating conditions (7.9 ± 2.4 and 8.3 ± 1.9 mmHg, respectively). However, CVC was not different between normocapnia and hypercapnia under either thermal condition (normothermia: 0.42 ± 0.24 vs. 0.39 ± 0.21 flux units/mmHg for normocapnia and hypercapnia, respectively; heat stress: 1.89 ± 0.67 vs. 1.92 ± 0.63 flux units/mmHg for normocapnia and hypercapnia, respectively).
Discussion:
Based on these findings, mild hypercapnia is unlikely to impair heat dissipation by reducing cutaneous vasodilation
Radiative decay Z_H-> \gamma A_H in the little Higgs model with T-parity
In the little Higgs model with T-parity (LHTM), the only tree-level
kinematically allowed two-body decay of the Z_H boson is Z_H-> A_H H and thus
one-loop induced two-body decays may have a significant rate. We study the
Z_H-> \gamma A_H decay, which is induced at the one-loop level by a fermion
triangle and is interesting as it depends on the mechanism of anomaly
cancellation of the model. All the relevant two- and three-body decays of the
Z_H gauge boson arising at the tree-level are also calculated. We consider a
small region of the parameter space where the scale of the symmetry breaking f
is still allowed to be as low as 500 GeV by electroweak precision data. We
first analyze the scenario of a Higgs boson with a mass of 120 GeV. We found
that the Z_H->\gamma A_H branching ratio can be of the order of a tree-level
three-body decay and may be at the reach of detection at the LHC for f close to
500 GeV, but it may be difficult to detect for f=1 TeV. There is also an
scenario where the Higgs boson has an intermediate mass such that the Z_H-> A_H
H decay is closed, the Z_H-> \gamma A_H gets considerably enhanced and the
chances of detection get a large boost.Comment: 19 pages, 9 figures, 2 table
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