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Register a new userA 96 GeV Higgs Boson in the 2HDMS: $e^+e^-$ collider prospects
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The CMS collaboration reported a $sim 3 , sigma$ (local) excess at $96;$GeV in the search for light Higgs-boson decaying into two photons. This mass coincides with a $sim 2 , sigma$ (local) excess in the $bbar b$ final state at LEP. We show an interpretation of these possible signals as the lightest Higgs boson in the 2 Higgs Doublet Model with an additional complex Higgs singlet (2HDMS). The interpretation is in agreement with all experimental and theoretical constraints. We concentrate on the 2HDMS type II, which resembles the Higgs and Yukawa structure of the Next-to Minimal Supersymmetric Standard Model. We discuss the experimental prospects for constraining our explanation at future $e^+e^-$ colliders, with concrete analyses based on the ILC prospects.
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We discuss a $sim 3,sigma$ signal (local) in the light Higgs-boson search in the diphoton decay mode at $sim 96$ GeV as reported by CMS, together with a $sim 2,sigma$ excess (local) in the $b bar b$ final state at LEP in the same mass range. We interpret this possible signal as a Higgs boson in the 2 Higgs Doublet Model with an additional real Higgs singlet (N2HDM). We find that the lightest Higgs boson of the N2HDM can perfectly fit both excesses simultaneously, while the second lightest state is in full agreement with the Higgs-boson measurements at 125 GeV, and the full Higgs-boson sector is in agreement with all Higgs exclusion bounds from LEP, the Tevatron and the LHC as well as other theoretical and experimental constraints. We show that only the N2HDM type II and IV can fit both the LEP excess and the CMS excess with a large ggF production component at $sim 96$ GeV. We derive bounds on the N2HDM Higgs sector from a fit to both excesses and describe how this signal can be further analyzed at the LHC and at future $e^+e^-$ colliders, such as the ILC.
A strong candidate for the Standard Model Scalar boson, H(126), has been discovered by the Large Hadron Collider (LHC) experiments. In order to study this fundamental particle with unprecedented precision, and to perform precision tests of the closure of the Standard Model, we investigate the possibilities offered by An e+e- storage ring collider. We use a design inspired by the B-factories, taking into account the performance achieved at LEP2, and imposing a synchrotron radiation power limit of 100 MW. At the most relevant centre-of-mass energy of 240 GeV, near-constant luminosities of 10^34 cm^{-2}s^{-1} are possible in up to four collision points for a ring of 27km circumference. The achievable luminosity increases with the bending radius, and for 80km circumference, a luminosity of 5 10^34 cm^{-2}s^{-1} in four collision points appears feasible. Beamstrahlung becomes relevant at these high luminosities, leading to a design requirement of large momentum acceptance both in the accelerating system and in the optics. The larger machine could reach the top quark threshold, would yield luminosities per interaction point of 10^36 cm^{-2}s^{-1} at the Z pole (91 GeV) and 2 10^35 cm^{-2}s^{-1} at the W pair production threshold (80 GeV per beam). The energy spread is reduced in the larger ring with respect to what is was at LEP, giving confidence that beam polarization for energy calibration purposes should be available up to the W pair threshold. The capabilities in term of physics performance are outlined.
The recent discovery of a light Higgs boson has opened up considerable interest in circular e+e- Higgs factories around the world. We report on the progress of the TLEP concept since last year. TLEP is an e+e- circular collider capable of very high luminosities in a wide centre-of-mass (ECM) spectrum from 90 to 350 GeV. TLEP could be housed in a new 80 to 100 km tunnel in the Geneva region. The design can be adapted to different ring circumference (e.g. LEP3 in the 27 km LHC tunnel). TLEP is an ideal complementary machine to the LHC thanks to high luminosity, exquisite determination of ECM and the possibility of four interaction points, both for precision measurements of the Higgs boson properties and for precision tests of the closure of the Standard Model from the Z pole to the top threshold.
We consider the possibility of a 120x120 GeV e+e- ring collider in the LHC tunnel. A luminosity of 10^34/cm2/s can be obtained with a luminosity life time of a few minutes. A high operation efficiency would require two machines: a low emittance collider storage ring and a separate accelerator injecting electrons and positrons into the storage ring to top up the beams every few minutes. A design inspired from the high luminosity b-factory design and from the LHeC design report is presented. Statistics of over 10^4 HZ events per year per experiment can be contemplated for a Standard Higgs Boson mass of 115-130 GeV.
We study the double Higgs boson production processes $e^+e^- to hh fbar{f}$ ($f eq t$) with $h$ being the 125 GeV Higgs boson in the two-Higgs-doublet model with a softly-broken $Z_2$ symmetry. The cross section can be significantly enhanced, typically a few hundreds percent, as compared to the standard model prediction due to resonant effects of heavy neutral Higgs bosons, which becomes important in the case without the alignment limit. We find a strong correlation between the enhancement factor of the cross section and the scaling factor of the $hfbar{f}$ couplings under constraints from perturbative unitarity, vacuum stability and current experimental data at the LHC as well as the electroweak precision data.
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