An experiment (E166) at the Stanford Linear Accelerator Center has demonstrated a scheme in which a multi-GeV electron beam passed through a helical undulator to generate multi-MeV, circularly ...polarized photons which were then converted in a thin target to produce positrons (and electrons) with longitudinal polarization above 80% at 6 MeV. The results are in agreement with GEANT4 simulations that include the dominant polarization-dependent interactions of electrons, positrons, and photons in matter.
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The ”Snowmass Points and Slopes” (SPS) are a set of benchmark points and parameter lines in the MSSM parameter space corresponding to different scenarios in the search for Supersymmetry at present ...and future experiments. This set of benchmarks was agreed upon at the 2001 ”Snowmass Workshop on the Future of Particle Physics” as a consensus based on different existing proposals.
The particle discovered in the Higgs boson searches at the LHC with a mass of about 125 GeV is compatible within the present uncertainties with the Higgs boson predicted in the Standard Model (SM), ...but it could also be identified with one of the neutral Higgs bosons in a variety of beyond the SM (BSM) theories with an extended Higgs sector. The possibility that an additional Higgs boson (or even more than one) could be lighter than the state that has been detected at 125 GeV occurs generically in many BSM models and has some support from slight excesses that were observed above the background expectations in Higgs searches at LEP and at the LHC. The couplings between additional Higgs fields and the electroweak gauge bosons in BSM theories could be probed by model-independent Higgs searches at lepton colliders. We present a generator-level extrapolation of the limits obtained at LEP to the case of a future
e
+
e
-
collider, both for the search where the light Higgs boson decays into a pair of bottom quarks and for the decay-mode-independent search utilising the recoil method. We find that at the ILC with a centre-of-mass energy of 250 GeV, an integrated luminosity of 500 fb
-
1
and polarised beams, the sensitivity to a light Higgs boson with reduced couplings to gauge bosons is improved by more than an order of magnitude compared to the LEP limits and goes much beyond the projected indirect sensitivity of the HL-LHC with 3000 fb
-
1
from the rate measurements of the detected state at 125 GeV.
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Recently, a
γ
γ
collider based on the existing 17.5 GeV linac of the European XFEL has been proposed. High-energy photons will be generated by Compton scattering of laser photons with a wavelength of ...0.5–1
μ
m
on electrons. Such a photon collider covers the range of invariant masses
W
γ
γ
<
12
Ge
V
/
c
2
. The physics program includes spectroscopy of
C
-even resonances (
c
-,
b
-quarkonia, 4-quark states, glueballs) in various
J
P
states. Variable circular and linear polarizations will help in determining the quantum numbers. In this paper, we present a summary of measured and predicted two-photon widths of various resonances in the mass region 3–12
Ge
V
/
c
2
and investigate the experimental possibility of observing these heavy two-photon resonances under the conditions of a large multi-hadron background. Registration of all final particles is assumed. The minimum values of
Γ
γ
γ
(
W
)
are obtained at which resonances can be detected at a
5
σ
confidence level in 1 year of operation.
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6.
Undulator-based production of polarized positrons Alexander, G.; Barley, J.; Batygin, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2009, Volume:
610, Issue:
2
Journal Article
Peer reviewed
Open access
Full exploitation of the physics potential of a future International Linear Collider will require the use of polarized electron and positron beams. Experiment E166 at the Stanford Linear Accelerator ...Center (SLAC) has demonstrated a scheme in which an electron beam passes through a helical undulator to generate photons (whose first-harmonic spectrum extended to 7.9
MeV) with circular polarization, which are then converted in a thin target to generate longitudinally polarized positrons and electrons. The experiment was carried out with a 1-m-long, 400-period, pulsed helical undulator in the Final Focus Test Beam (FFTB) operated at 46.6
GeV. Measurements of the positron polarization have been performed at five positron energies from 4.5 to 7.5
MeV. In addition, the electron polarization has been determined at 6.7
MeV, and the effect of operating the undulator with a ferrofluid was also investigated. To compare the measurements with expectations, detailed simulations were made with an upgraded version of G
eant4
that includes the dominant polarization-dependent interactions of electrons, positrons, and photons with matter. The measurements agree with calculations, corresponding to 80% polarization for positrons near 6
MeV and 90% for electrons near 7
MeV.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract
Recently, a
$$\gamma \gamma $$
γ
γ
collider based on the existing 17.5 GeV linac of the European XFEL has been proposed. High-energy photons will be generated by Compton scattering of laser ...photons with a wavelength of 0.5–1
$${\,\upmu \mathrm m}$$
μ
m
on electrons. Such a photon collider covers the range of invariant masses
$$W_{\gamma \gamma } <12$$
W
γ
γ
<
12
$${\mathrm {\,Ge V\!/}c^2}$$
Ge
V
/
c
2
. The physics program includes spectroscopy of
$$ C $$
C
-even resonances (
c
-,
b
-quarkonia, 4-quark states, glueballs) in various
$$J^P$$
J
P
states. Variable circular and linear polarizations will help in determining the quantum numbers. In this paper, we present a summary of measured and predicted two-photon widths of various resonances in the mass region 3–12
$${\mathrm {\,Ge V\!/}c^2}$$
Ge
V
/
c
2
and investigate the experimental possibility of observing these heavy two-photon resonances under the conditions of a large multi-hadron background. Registration of all final particles is assumed. The minimum values of
$$\varGamma _{\gamma \gamma }(W)$$
Γ
γ
γ
(
W
)
are obtained at which resonances can be detected at a
$$5\sigma $$
5
σ
confidence level in 1 year of operation.
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8.
Physics at the e+e- linear collider Moortgat-Pick, G.; Baer, H.; Battaglia, M. ...
The European physical journal. C, Particles and fields,
08/2015, Volume:
75, Issue:
8
Journal Article
Peer reviewed
Open access
A comprehensive review of physics at an
e
+
e
-
linear collider in the energy range of
s
=
92
GeV–3 TeV is presented in view of recent and expected LHC results, experiments from low-energy as well ...as astroparticle physics. The report focusses in particular on Higgs-boson, top-quark and electroweak precision physics, but also discusses several models of beyond the standard model physics such as supersymmetry, little Higgs models and extra gauge bosons. The connection to cosmology has been analysed as well.
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Charginos \(\tilde{\chi}^\pm\) and neutralinos \(\tilde{\chi}^0\) in supersymmetric theories can be produced copiously at \(e^+e^-\) colliders and their properties can be measured with high accuracy. ...Consecutively to the chargino system, in which the SU(2) gaugino parameter \(M_2\), the higgsino mass parameter \(\mu\) and \(\tan\beta\) can be determined, the remaining fundamental supersymmetry parameter in the gaugino/higgsino sector of the minimal supersymmetric extension of the Standard Model, the U(1) gaugino mass \(M_1\), can be analyzed in the neutralino system, including its modulus and its phase in CP–noninvariant theories. The CP properties of the neutralino system are characterized by unitarity quadrangles. Analytical solutions for the neutralino mass eigenvalues and the mixing matrix are presented for CP–noninvariant theories in general. They can be written in compact form for large supersymmetric mass parameters. The closure of the neutralino and chargino systems can be studied by exploiting sum rules for the pair-production processes in \(e^+e^-\) collisions. Thus the picture of the non–colored gaugino and higgsino complex in supersymmetric theories can comprehensively be reconstructed in these experiments.
The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics ...return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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