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Z-peaked excess from heavy gluon decays to vector-like quarks  [PDF]
Natascia Vignaroli
Physics , 2015, DOI: 10.1103/PhysRevD.91.115009
Abstract: A 3 sigma excess has been recently announced by ATLAS in events with Z-peaked dilepton pairs, jets, and large transverse missing energy. We interpret this finding in the context of composite Higgs / RS theories. We find that composite Higgs theories with custodial symmetry protection to the $Zb\bar{b}$ coupling predict a significant contribution to $ZZbb$ (and to $hhbb$) final states coming from heavy gluon decays to pairs of bottom-partner vector-like quarks. The heavy gluon to vector-like quarks signal is largely accepted by the ATLAS selection if one of the $Z$ boson in the $ZZbb$ final state decays leptonically and the other to neutrinos. For a bottom partner of $\sim$900 GeV, we find that the ATLAS excess can be reproduced by composite Higgs models, in an experimentally allowed parameter space, for heavy gluon masses roughly in a range 1.87 - 2.15 TeV and for heavy gluon couplings to light quarks within $\sim(0.3-0.65) g_S$. We briefly discuss the implication of this result for future experimental tests.
Few-Body Systems Composed of Heavy Quarks  [PDF]
Ning Li,Zhi-Feng Sun,Jun He,Xiang Liu,Zhi-Gang Luo,Shi-Lin Zhu
Physics , 2012, DOI: 10.1007/s00601-012-0564-2
Abstract: Within the past ten years many new hadrons states were observed experimentally, some of which do not fit into the conventional quark model. I will talk about the few-body systems composed of heavy quarks, including the charmonium-like states and some loosely bound states.
Heavy flavor dibaryons  [PDF]
T. F. Carames,A. Valcarce
Physics , 2015, DOI: 10.1103/PhysRevD.92.034015
Abstract: We study the two-baryon system with two units of charm looking for the possible existence of a loosely bound state resembling the $H$ dibaryon. We make use of a chiral constituent quark model tuned in the description of the baryon and meson spectra as well as the $NN$ interaction. The presence of the heavy quarks makes the interaction simpler than in light baryon systems. We analyze possible quark-Pauli effects that would be present in spin-isospin saturated channels. Our results point to the non-existence of a charmed $H$-like dibaryon, although it may appear as a resonance above the $\Lambda_c\Lambda_c$ threshold.
Long-lived heavy quarks : a review  [PDF]
Mathieu Buchkremer,Alexander Schmidt
Physics , 2012,
Abstract: We review the theoretical and experimental situation for long-lived heavy quarks, or bound states thereof, arising in simple extensions of the Standard Model. If these particles propagate large distances before their decay, they give rise to specific signatures requiring dedicated analysis methods. In particular, vector-like quarks with negligible couplings to the three known families could have eluded the past experimental searches. While most analyses assume prompt decays at the production vertex, novel heavy quarks might lead to signatures involving displaced vertices, new hadronic bound states, or decays happening outside of the detector acceptance. We perform reinterpretations of existing searches for short- and long-lived particles, and give suggestions on how to extend their reach to long-lived heavy quarks.
Spectroscopy of Mesons with Heavy Quarks
Zhu, Shi-Lin
High Energy Physics - Phenomenology , 2007, DOI: 10.1016/j.nuclphysa.2008.02.251
Abstract: I will give a concise overview of mesons with heavy quarks including p-wave charmed mesons and charmonium (or charmonium-like) states such as X(3872), Y(4260), X(3940), Y(3940), Z(3930) etc. The effect from the nearby S-wave open channels on the quark model spectrum is emphasized.
Possible Deuteron-like Molecular States Composed of Heavy Baryons  [PDF]
Ning Lee,Zhi-Gang Luo,Xiao-Lin Chen,Shi-Lin Zhu
Physics , 2011, DOI: 10.1103/PhysRevD.84.014031
Abstract: We perform a systematic study of the possible loosely bound states composed of two charmed baryons or a charmed baryon and an anti-charmed baryon within the framework of the one boson exchange (OBE) model. We consider not only the $\pi$ exchange but also the $\eta$, $\rho$, $\omega$, $\phi$ and $\sigma$ exchanges. The $S-D$ mixing effects for the spin-triplets are also taken into account. With the derived effective potentials, we calculate the binding energies and root-mean-square (RMS) radii for the systems $\Lambda_c\Lambda_c(\bar{\Lambda}_c)$, $\Xi_c\Xi_c(\bar{\Xi}_c)$, $\Sigma_c\Sigma_c(\bar{\Sigma}_c)$, $\Xi_c^\prime\Xi_c^\prime(\bar{\Xi}_c^\prime)$ and $\Omega_c\Omega_c(\bar{\Omega}_c)$. Our numerical results indicate that: (1) the H-dibaryon-like state $\Lambda_c\Lambda_c$ does not exist; (2) there may exist four loosely bound deuteron-like states $\Xi_c\Xi_c$ and $\Xi_c^\prime\Xi_c^\prime$ with small binding energies and large RMS radii.
Search for heavy vector-like quarks coupling to light quarks in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector  [PDF]
ATLAS Collaboration
Physics , 2011, DOI: 10.1016/j.physletb.2012.03.082
Abstract: This letter presents a search for singly produced vector-like quarks, Q, coupling to light quarks, q. The search is sensitive to both charged current (CC) and neutral current (NC) processes, p p --> Q q --> W q q' and p p --> Q q --> Z q q' with a leptonic decay of the vector gauge boson. In 1.04/fb of data taken in 2011 by the ATLAS experiment at a center-of-mass energy sqrt(s) = 7 TeV, no evidence of such heavy vector-like quarks is observed above the expected Standard Model background. Limits on the heavy vector-like quark production cross section times branching ratio as a function of mass m_Q are obtained. For a coupling kappa_(qQ) = v/m_Q, where v is the Higgs vacuum expectation value, 95% C.L. lower limits on the mass of a vector-like quark are set at 900 GeV and 760 GeV from CC and NC processes, respectively.
Tests of possible non standard properties of the heavy quarks and the Higgs boson  [PDF]
G. J. Gounaris,J. Layssac,D. T. Papadamou,G. Tsirigoti,F. M. Renard
Physics , 1997,
Abstract: We discuss the sensitivity of the processes e+e- to b b(bar), e+e- to t t(bar) and gamma gamma to H to certain residual New Physics interactions affecting the heavy quark and Higgs boson sector. With a linear collider of 500 GeV, one should be able to detect and identify such effects with a characteristic scale up to 50 TeV.
Hadrons with Two Heavy Quarks  [PDF]
Jean-Marc Richard
Physics , 1994,
Abstract: We review the spectroscopy and some properties of hadrons containing two charmed quarks, or more generally, two heavy quarks. This includes heavy baryons such as $(bcu)$, and possible exotic multiquark states.
Search for heavy bottom-like quarks in 4.9 inverse femtobarns of pp collisions at sqrt(s) = 7 TeV  [PDF]
CMS Collaboration
Physics , 2012, DOI: 10.1007/JHEP05(2012)123
Abstract: Results are presented from a search for heavy bottom-like quarks, pair-produced in pp collisions at sqrt(s) = 7 TeV, undertaken with the CMS experiment at the LHC. The b' quarks are assumed to decay exclusively to tW. The b' anti-b' to t W(+) anti-t W(-) process can be identified by its distinctive signatures of three leptons or two leptons of same charge, and at least one b-quark jet. Using a data sample corresponding to an integrated luminosity of 4.9 inverse femtobarns, observed events are compared to the standard model background predictions, and the existence of b' quarks having masses below 611 GeV is excluded at 95% confidence level.
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