Low mass glueballs in the meson spectrum

The spectrum of bound states of gluons is discussed within the MIT bag model. We argue that (1) contrary to previous analysis there is no light exotic 1^?+ state in the two gluon sector, (2) experiments on the three gluon sector can clearly differentiate the bag model from other models, (3) the state seen in J/ψ radiative decays at 1.4 GeV is most likely a pseudoscalar glueball, and (4) there should be a second 2⁺⁺ state underneath the f(1270) resonance.     

Mass bounds of the lightest CP-even Higgs boson in the two-Higgs-doublet model

The upper and the lower bounds of the lightest CP-even Higgs-boson mass (m_h) are discussed in the two-Higgs-doublet model (2HDM) with a softly-broken discrete symmetry. They are obtained as a function of a cut-off scale Λ (≤10¹⁹ GeV) by imposing the conditions in which the running coupling constants neither blow up nor fall down below Λ. In comparison with the standard model (SM), although the upper bound does not change very much, the lower bound is considerably reduced. In the decoupling regime where only one Higgs boson (h) becomes much lighter than the others, the lower bound is given, for example, by about 100 GeV for Λ=10¹⁹ GeV and m_t=175 GeV, which is smaller by about 40 GeV than the corresponding lower bound in the SM. In generic cases, m_h is no longer bounded from below by these conditions. If we consider the b→sγ constraint, small values of m_h are excluded in Model II of the 2HDM.     

Ultra heavy fermion bound states via Higgs exchange

We study the characteristic features of the ultra heavy fermion bound state via Higgs exchange. The constraint under which such a bound state occurs is presented. For a typical example of Higgs and fermion mass, M_H≅ 100 GeV / c² and M_F≅ 700 GeV/c², the wave function at the origin of the bound states via Higgs exchange becomes about 100 times larger than that via gluon exchange.     

Probing High-Scale and Split Supersymmetry with Higgs mass measurements

We study the range of Higgs masses predicted by High-Scale Supersymmetry and by Split Supersymmetry, using the matching condition for the Higgs quartic coupling determined by the minimal field content. In the case of Split Supersymmetry, we compute for the first time the complete next-to-leading order corrections, including two-loop renormalization group equations and one loop threshold effects. These corrections reduce the predicted Higgs mass by a few GeV. We investigate the impact of the recent LHC Higgs searches on the scale of supersymmetry breaking. In particular, we show that an upper bound of 127 GeV on the Higgs mass implies an upper bound on the scale of Split Supersymmetry of about ¹⁰⁸ GeV, while no firm conclusion can yet be drawn for High-Scale Supersymmetry.     

An amplitude analysis of ππ scattering from new data on the reaction π−p→π+π−n

We have carried out a partial-wave analysis of ππ scattering in the mass range 1.0 to 2.08 GeV/c². We find solutions similar to those obtained in previous analyses below 1.8 GeV/c² but, in addition, we obtain a new solution which does not suffer from violations of unitarity and is compatible with data from other channels. This solution, when continued to 2.08 GeV/c², shows a g meson with mass and width of 1.734± 0.010 GeV/c²and 0.322±0.035 GeV/c² respectively, and an h meson with mass 1.935±0.013 GeV/c²and width 0.263±0.057 GeV/c². The L = 2 partial wave contains the f meson and an additional resonance with parameters m = 1.502±0.025 Gev/c², Γ = 0.165±0.042 GeV/c²and x = 0.19±0.03. If we associate this state with the f′(1514), our ππ branching fraction is considerably higher than previous determinations. An SU(3) fit to the 2⁺ nonet yields a mixing angle of 38.4± 1.3°.     

Search for new SS states in the K− induced K+K− system

Results from the first PWA of the K⁺K^? system produced by incident K^?, are presented in the mass range from the threshold to 1.70 GeV. In the P and D waves only the φ and f′ mesons are observed and their production mechanism studied. A broad S wave peaking at 1.4 GeV is observed but the lack of information about its phase makes the search for new 0⁺⁺ mesons inconclusive.     

Nucleosynthesis bounds in gauge-mediated supersymmetry breaking theories

In gauge-mediated supersymmetry breaking theories the next-to-lightest supersymmetric particle can decay during or after the nucleosynthesis epoch. The decay products such as photons and hadrons can destroy the light element abundances. Restricting the damage that these decays can do leads to constraints on the abundance and lifetime of the NLSP. We compute the freezeout abundance of the NLSP by including all coannihilation thresholds which are particularly important in the case in which the NLSP is the lightest stau. We find that the upper bound on the messenger scale can be as stringent as 10¹² GeV when the NLSP is the lightest neutralino and 10¹³ GeV when the NLSP is the lightest stau. Our findings disfavour models of gauge mediation where the messenger scale is close to the GUT scale or results from balancing renormalisable interactions with non-renormalisable operators at the Planck scale. When combined with the requirement of no gravitino overabundance, our bound implies that the reheating temperature after inflation must be less than 10⁷ GeV.     

Final results from DELPHI on the searches for SM and MSSM neutral Higgs bosons

These final results from DELPHI searches for the Standard Model (SM) Higgs boson, together with benchmark scans of the Minimal Supersymmetric Standard Model (MSSM) neutral Higgs bosons, used data taken at centre-of-mass energies between 200 and 209 GeV with a total integrated luminosity of 224 pb^-1. The data from 192 to 202 GeV are reanalysed with improved b-tagging for MSSM final states decaying to four b-quarks. The 95% confidence level lower mass bound on the Standard Model Higgs boson is 114.1 GeV/c ². Limits are also given on the lightest scalar and pseudo-scalar Higgs bosons of the MSSM.Received: 7 March 2003, Revised: 30 September 2003, Published online: 3 December 2003     

Search for excited leptons in e+e- collisions at \sqrt{s}=189–209 GeV

A search for excited lepton production in e⁺e^- collisions was performed using the data collected by the DELPHI detector at LEP at centre-of-mass energies ranging from 189 GeV to 209 GeV, corresponding to an integrated luminosity of approximately 600 pb^-1. No evidence for excited lepton production was found. In searches for pair-produced excited leptons, lower mass limits were established in the range 94–103 GeV/c², depending on the channel and model assumptions. In searches for singly-produced excited leptons, upper limits on the parameter f/Λ were established as a function of the mass.     

Large width gluonic bound state in J/Ψ radiative decay

The photon spectrum in the radiative decay of J/Ψ is analysed with a Breit-Wigner and background terms based on a duality hypothesis. We obtain a fit with a resonance, which is considered to be a 2⁺ gluonic bound state, of a mass around 2 GeV and a width around 0.6 GeV. Implications of the ? and toponium decays are also discussed.     

Total cross section for inclusive electron scattering in the lowQ 2 region

Absolute cross sections for inclusive electron scattering on H, D, Be, Al, and Si have been measured in the kinematical region 0.08 (GeV/c)²<Q ²<1.0 (GeV/c)² and 0.3 GeV<v<6.5 GeV. The measurements have been performed at incident energies of 3, 5, 6, and 7 GeV and at the fixed scattering angle of 10°. A careful treatment of radiative corrections due to elastic electron nucleus scattering, quasielastic and inelastic scattering on the bound nucleons has been applied to the measured cross sections. The comparison of the nuclear cross sections with the elementary ones leads to a value ofA _eff<A with a rapid onset of this effect at small values of the scaling variablex′.     

Constraints on cosmologically regenerated gravitinos

Cosmological constraints on the regenerated abundance of gravitinos as a function of the maximum reheating temperature T_h are examined. We combine the bound that arises in order for stable photinos produced by gravitino decays to not overdominate the mass density of the universe together with that inferred from the distortions produced in the cosmic microwave background radiation as well as constraints from the observed deuterium and ³He abundances. This suffices to constrain T_h to be below between 10¹⁷ and 10¹⁰ GeV for gravitions in the mass below ～ 10 TeV. More massive gravitinos, however, could be produced at T_h<10¹⁴ GeV.     

Is X(3872) really a molecular state?

After taking into account both the pion and sigma meson exchange potential, we have performed a dynamical calculation of the D⁰D̄^*0 system. The σ meson exchange potential is repulsive from heavy quark symmetry and numerically important for a loosely bound system. Our analysis disfavors the interpretation of X(3872) as a loosely bound molecular state if we use the experimental D^*Dπ coupling constant g=0.59 and a reasonable cutoff around 1 GeV, which is the typical hadronic scale. Bound state solutions with negative eigenvalues for the DD̄^* system exist only with either a very large coupling constant (twice the experimental value) or a large cutoff (Λ ∼ 6 GeV or β ∼ 6 GeV²). In contrast, there probably exists a loosely bound S-wave BB̄^* molecular state. Once produced, such a molecular state would be rather stable, since its dominant decay mode is the radiative decay through B^*→Bγ. Experimental search of these states will be very interesting. PACS  12.39.Pn; 12.40.Yx; 13.75.Lb     

Search for narrow resonances in e+e− annihilation at petra

We have performed a search for narrow resonances in the center of mass energy range from 29.90 to 31.46 GeV using the e⁺e^? storage ring PETRA at DESY. We present the total cross section for hadron production and an upper limit for resonance production, indicating that no bound state of charge-$\text{2}\text{3}$ quarks exists in this energy range.     

Study of the ϱ' (1600) using bound on even g-parity e+e− hadronic cross section

Inequality involving σ(e⁺e^? → nπ), n = even > 2 is derived in the 1.6 GeV region and is used to get an upper bound on the 2π branching ratio of ?′ (1600).     

Flowering to bloom of PeV scale supersymmetric left–right symmetric models

Unified models incorporating right-handed neutrino in a symmetric way generically possess parity symmetry. If this is broken spontaneously, it results in the formation of domain walls in the early Universe, whose persistence is unwanted. A generic mechanism for the destabilization of such walls is a small pressure difference signalled by difference in free energy across the walls. It is interesting to explore the possibility of such effects in conjunction with the effects that break supersymmetry in a phenomenologically acceptable way. This possibility when realized in the context of several scenarios of supersymmetry breaking, leads to an upper bound on the scale of spontaneous parity breaking, often much lower than the GUT scale. In the left–right symmetric models studied, the upper bound is no higher than 10¹¹ GeV but a scale as low as 10⁵ GeV is acceptable.     

Axion constraints from white dwarf cooling times

Hypothetical, pseudoscalar particles would be abundantly emitted from the interior of white dwarfs through bremsstrahlung processes. These stars would then rapidly cool. From the observed number of hot degenerates we find a new bound on the Yukawa coupling to electrons of g < 4 × 10⁻¹³. For “invisible axions” this translates into a new bound on the Peccei-Quinn scale of v > 1 × 10⁹ GeV, corresponding to m_a < 3 × 10⁻² eV.     

μ− meson catalysis of nuclear fusion in a mixture of deuterium and tritium

Due to the existence of a weakly bound state of the mesic molecule dt μ^? meson in a mixture of deuterium and tritium can catalyze ～ 10² of the fusion reactions dt μ →⁴He + n + μ^? + 17.6 MeV and release ～ 2 GeV of energy.     

Search for long-lived particles in 200 GeV/c proton-nucleon collisions

A search for long-lived particles (τ ? 10^?8 sec), with changes $\text{±}\text{2}\text{3}\text{, ± 1, ±}\text{4}\text{3}\text{and}\text{± 2}$, produced in 200 GeV pN collisions was performed at the CERN-SPS in a secondary beam equipped with superconducting r.f. separators. Upper limits were obtained for the production of long-lived hadrons and leptons. For charge - 1 particles the limits are at the level of 10^?7 of the pions at a mass m = 0.2 GeV and reach the 10^?11 level from $\text{3}\text{to}\text{8}\text{GeV}$. The production of light antinuclei was measured. The cross sections for ³He production are (1.3 ± 0.3) and (1.9 ± 0.3) × 10^?34 cm²/sr · GeV/c at 21 and 47.4 GeV/c respectively; for t the cross section is (7.6 ± 0.9) × 10^?34 cm²/sr · GeV/c at 23.7 GeV/c.