Higgs Boson Decays into Single Photon plus Unparticle

The decay of the standard model Higgs boson into a single photon and a vector unparticle through a one-loop process is studied. For an intermediate mass Higgs boson, this single photon plus unparticle mode can have a branching ratio comparable with the two-photon discovery mode. The emitted photon has a continuous energy spectrum encoding the nature of the recoil unparticle. It can be measured in precision studies of the Higgs boson after its discovery.Comment: 10 pages, 3 figure

Perturbative QCD Fragmentation Functions for BcB_c and Bc∗B_c^* Production

The dominant production mechanism for ${\bar b} c$ bound states in high energy processes is the production of a high energy ${\bar b}$ or $c$ quark, followed by its fragmentation into the ${\bar b} c$ state. We calculate the fragmentation functions for the production of the S-wave states $B_c$ and $B_c^*$ to leading order in the QCD coupling constant. The fragmentation probabilities for ${\bar b} \rightarrow B_c$ and ${\bar b} \rightarrow B_c^*$ are approximately $2.2 \times 10^{-4}$ and $3.1 \times 10^{-4}$, while those for $c \rightarrow B_c$ and $c \rightarrow B_c^*$ are smaller by almost two orders of magnitude.Comment: Latex, 12 pages, 3 figures available upon request, NUHEP-TH-93-

Helicity Probabilities For Heavy Quark Fragmentation Into Excited Mesons

In the fragmentation of a heavy quark into a heavy meson whose light degrees of freedom have angular momentum $3/2$, all the helicity probabilities are completely determined in the heavy quark limit up to a single probability $w_{3/2}$. We point out that this probability depends on the longitudinal momentum fraction $z$ of the meson and on its transverse momentum $p_\bot$ relative to the jet axis. We calculate $w_{3/2}$ as a function of scaling variables corresponding to $z$ and $p_\bot$ for the heavy quark limit of the perturbative QCD fragmentation functions for $b$ quark to fragment into $(b \bar c)$ mesons. In this model, the light degrees of freedom prefer to have their angular momentum aligned transverse to, rather than along, the jet axis. Implications for the production of excited heavy mesons, like $D^{**}$ and $B^{**}$, are discussed.Comment: 10 pages, Latex file plus 3 figures with postscript files appended at the en

Perturbative QCD Fragmentation Functions for Production of P-wave Mesons with Charm and Beauty

We calculate the leading order QCD fragmentation functions for the production of $P$-wave charmed beauty mesons. Long-distance effects are factored into two nonperturbative parameters: the derivative of the radial wavefunction at the origin and a second parameter related to the probability for a $(\bar b c)$ heavy quark pair that is produced in a color-octet $S$-wave state to form a color-singlet $P$-wave bound state. The four $2P$ states and those $3P$ states which lie below the $BD$ flavor threshold eventually all decay into the $1S$ ground state $B_c$ through hadronic cascades or by emitting photons. The total fragmentation probabilities for production of the $1S$ ground state $B_c$ from the cascades of the $2P$ and $3P$ states are about $1.7 \times 10^{-4}$ and $2.3 \times 10^{-4}$ respectively. Thus the direct production of the $P$-wave states via fragmentation may account for a significant fraction of the inclusive production rate of the $B_c$ at large transverse momentum in high energy colliders. Our analytic results for the $P$-wave fragmentation functions disagree with those obtained earlier in the literature.Comment: 31 pages, Latex file, 1 figure (postscript file appended at the end

Hadronic Production of S-wave and P-wave Charmed Beauty Mesons via Heavy Quark Fragmentation

At hadron colliders the dominant production mechanism of $(\bar bc)$ mesons with large transverse momentum is due to parton fragmentation. We compute the rates and transverse momentum spectra for production of S-wave and P-wave $(\bar b c)$ mesons at the Tevatron via the direct fragmentation of the bottom antiquark as well as the Altarelli-Parisi induced gluon fragmentation. Since all the radially and orbitally excited $(\bar b c)$ mesons below the $BD$ flavor threshold will cascade into the pseudoscalar ground state $B_c$ through electromagnetic and/or hadronic transitions, they all contribute to the inclusive production of $B_c$. The contributions of the excited S-wave and P-wave states to the inclusive production of $B_c$ are 58 and 23\%, respectively, and hence significant.Comment: Changes are made in the Discussio

Distinguishing Various Models of the 125 GeV Boson in Vector Boson Fusion

The hint of a new particle around 125 GeV at the LHC through the decay modes of diphoton and a number of others may point to quite a number of possibilities. While at the LHC the dominant production mechanism for the Higgs boson of the standard model and some other extensions is via the gluon fusion process, the alternative vector boson fusion is more sensitive to electroweak symmetry breaking through the gauge-Higgs couplings and therefore can be used to probe for models beyond the standard model. In this work, using the well known dijet-tagging technique to single out the vector boson fusion mechanism, we investigate its capability to discriminate a number of models that have been suggested to give an enhanced inclusive diphoton production rate, including the standard model Higgs boson, fermiophobic Higgs boson, Randall-Sundrum radion, inert-Higgs-doublet model, two-Higgs-doublet model, and the MSSM. The rates in vector-boson fusion can give more information of the underlying models to help distinguishing among the models.Comment: 31 pages, 3 figures; in this version some wordings are change

Higgs-Boson Decay to Four Fermions Including a Single Top Quark Below ttˉt \bar t Threshold

The rare decay modes Higgs $\rightarrow$ four light fermions, and Higgs $\rightarrow$ single top-quark + three light fermions for $m_t<M_H<2m_t$, are presented, and phenomenologically interpreted. The angular correlation between fermion planes is presented as a test of the spin and intrinsic parity of the Higgs particle. In Higgs decay to single top, two tree-level graphs contribute in the standard model (SM); one couples the Higgs to $W^+W^-(\sim gM_W)$, and one to t\bar t(\sim g_{top\;yukawa}=m_t/246\GeV). The large Yukawa coupling for m_t>100\GeV makes the second amplitude competitive or dominant for most $M_H,m_t$ values. Thus the Higgs decay rate to single top directly probes the SM universal mechanism generating both gauge boson and fermion masses, and offers a means to infer the Higgs-$t \bar t$ Yukawa coupling when $H\rightarrow t \bar t$ is kinematically disallowed. We find that the modes $pp\rightarrow Xt\bar t(H\rightarrow t\bar b W^{(*)})$ at the SSC, and $e^+ e^-\rightarrow Z\,or\,\nu\bar{\nu} + (H\rightarrow t\bar b W^{(*)})$ at future high energy, high luminosity colliders, may be measureable if $2m_t$ is not too far above $M_H$. We classify non-standard Higgses as gaugeo-phobic, fermio-phobic or fermio-philic, and discuss the Higgs$\rightarrow$ single top rates for these classes.Comment: 30 pages, 6 figures (figures available upon request); VAND-TH-93/

Global Study of the Simplest Scalar Phantom Dark Matter Model

We present a global study of the simplest scalar phantom dark matter model. The best fit parameters of the model are determined by simultaneously imposing (i) relic density constraint from WMAP, (ii) 225 live days data from direct experiment XENON100, (iii) upper limit of gamma-ray flux from Fermi-LAT indirect detection based on dwarf spheroidal satellite galaxies, and (iv) the Higgs boson candidate with a mass about 125 GeV and its invisible branching ratio no larger than 40% if the decay of the Higgs boson into a pair of dark matter is kinematically allowed. The allowed parameter space is then used to predict annihilation cross sections for gamma-ray lines, event rates for three processes mono-b jet, single charged lepton and two charged leptons plus missing energies at the Large Hadron Collider, as well as to evaluate the muon anomalous magnetic dipole moment for the model.Comment: Matches JCAP accepted version. 25 pages, 7 figure

Heavy Quark Fragmentation Functions for D-wave Quarkonium and Charmed Beauty Mesons

At the large transverse momentum region, the production of heavy-heavy bound-states such as charmonium, bottomonium, and $\bar bc$ mesons in high energy $e^+e^-$ and hadronic collisions is dominated by parton fragmentation. We calculate the heavy quark fragmentation functions into the D-wave quarkonium and $\bar bc$ mesons to leading order in the strong coupling constant and in the non-relativistic expansion. In the $\bar b c$ meson case, one set of its D-wave states is expected to lie below the open flavor threshold. The total fragmentation probability for a $\bar b$ antiquark to split into the D-wave $\bar b c$ mesons is about $2 \times 10^{-5}$, which implies that only 2\% of the total pseudo-scalar ground state $B_c$ comes from the cascades of these orbitally excited states.Comment: 26 pages in RevteX and 3 figures in postscript. Also available at http://www.ph.utexas.edu/~cheung/paper.htm

Color-Octet J/ψJ/\psi Production in the Υ\Upsilon Decay

The direct production rate of $\psi$ in the $\Upsilon$ decay is shown to be dominated by the process $\Upsilon \to ggg^*$ followed by $g^* \to \psi$ via the color-octet mechanism proposed recently to explain the anomalous prompt charmonium production at the Tevatron. We show that this plausibly dominant process has a branching ratio compatible with the experimental data. Further experimental study in this channel is important to test the significance of the color-octet component of $c\bar c$ pair inside the $\psi$ system.Comment: 20 pages, Standard LaTeX, 2 figures; a couple of new processes added, but conclusion unchange