We consider a color octet scalar particle and its exotic decay in the channel gluon-$γ$ using an effective Lagrangian description for its strong and electromagnetic interactions. Such a state is present in many extensions of the Standard Model, and in particular in composite Higgs models with top partial compositeness, where couplings to photons arise via the Wess-Zumino-Witten term. We find that final states with one or two photons allow for a better reach at the LHC, even for small branching ratios. Masses up to $1.2$ TeV can be probed at the HL-LHC by use of all final states. Finally, we estimate the sensitivity of the hadronic FCC.
Color scalars are salient features of non-minimal SU(5) model, where Higgs sector is extended by 45-dimensional multiplet. We show that gauge coupling unification can be realized in this model with TeV octet scalar and intermediate (~10^6 GeV) color-triplet scalar at scale larger than 10^{15} GeV. We analyze the possible LHC signatures of these TeV octet scalars. We emphasize that multi-(b)-jet final states provide significant signal for direct probe of octet scalars at the LHC.
We report the recent progress in the studies of D-wave heavy quarkonia production from gluon fragmentation at the Tevatron and in Z^0 decays, and the D-wave charmonia production in B decays. We show that the color-octet contributions are of crucial importance to the production of D-wave quarkonia. Signals, as strong as that for J/ψand ψ^\prime, should be seen for the D-wave charmonium in the processes. These will provide a test of the color-octet production mechanism.
We study the effect of color octet scalars on the high transverse momenta four-jet cross section at the LHC. We consider both weak singlet and doublet scalars, concentrating on the case of small couplings to quarks. We find that a relatively early discovery at the LHC is possible for a range of scalar masses.
We study the possibility to probe the unpolarized and linearly polarized transverse momentum- dependent gluon distributions in unpolarized pp collision in charmonium and bottomonium produc- tion, employing non-relativistic QCD (NRQCD) based color octet model within transverse momentum dependent (TMD) factorization framework. The transverse momentum (p T ) and rapidity distributions of J/ψ and Υ(1S) at LHCb, RHIC and AFTER energies are estimated. Significant modulations in transverse momentum spectrum of quarkonium in the low p T region is obtained when contributions of linearly polarized gluon…
The short-distance coefficients for the color-octet 3S1 term in the fragmentation function for a gluon to split into heavy quarkonium states is calculated to order alpha_s^2. The gauge-invariant definition of the fragmentation function by Collins and Soper is employed. Ultraviolet divergences are removed using the MS-bar renormalization procedure. The longitudinal term in the fragmentation function agrees with a previous calculation by Beneke and Rothstein. The next-to-leading order correction to the transverse term disagrees with a previous calculation.
Color octet (pseudo)scalars, if they exist, will be copiously produced at the CERN Large Hadron Collider (LHC). However, their detection can become a very challenging task. In particular, if their decay into a pair of top quarks is kinematically forbidden, the main decay channel would be into two jets, with a very large background. In this Brief Report we explore the possibility of using anomaly-induced decays of the color octet pseudoscalars into gauge bosons to find them at the LHC.
We use the color-octet mechanism combined with the two gluon exchange model for the diffractive $J/ψ$ production in resolved photon processes. In the leading logarithmic approximation in QCD, we find that the diffractive $J/ψ$ production cross section is related to the off-diagonal gluon density of the proton, the gluon density of the photon and to the nonperturbative color-octet $^3 S_{1}^{(8)}$ matrix element of $J/ψ$. The cross section is found to be very sensitive to the gluon density of the photon. As a result, this process may provide a wide window for testing the two-gluon exchange mode…
One possible extension of the Standard Model scalar sector includes SU(2)_L doublet scalars that are color octets rather than singlets. We focus on models in which the couplings to fermions are consistent with the principle of minimal flavor violation (MFV), in which case these color octet scalars couple most strongly to the third generation of quarks. When the Yukawa coupling of color octet scalars to Standard Model fermions is less than unity, these states can live long enough to bind into color-singlet spin-0 hadrons, which we call octetonia. In this paper, we consider the phenomenology of …
Elements of the phenomenology of color-octet scalars (sgluons), as predicted in the hybrid N=1/N=2 supersymmetric model, are discussed in the light of forthcoming experiments at the CERN Large Hadron Collider.
New physics at the weak scale that can couple to quarks typically gives rise to unacceptably large flavor changing neutral currents. An attractive way to avoid this problem is to impose the principal of minimal flavor violation (MFV). Recently it was noted that in MFV only scalars with the same gauge quantum numbers as the standard model Higgs doublet or color octet scalars with the same weak quantum numbers as the Higgs doublet can couple to quarks. In this paper we compute the one-loop rate for production of a single color octet scalar through gluon fusion at the LHC, which can become greate…
Several models of new physics, such as grand unified theories, Pati-Salam models, chiral color models, etc., predict the existence of an $SU(2)_L$ doublet of color-octet scalars (COS). In the Manohar-Wise model, the Yukawa couplings of the COS are assumed to be consistent with Minimal Flavor Violation ensuring constraints from flavor physics are satisfied even for relatively light scalars. In this simple model we consider the production of color singlet bound states of COS that we call octetonium. Octetonium are mainly produced via gluon-gluon fusion and have significant production cross secti…
We compute the next-to-next-to-leading order QCD corrections to the gluon-fusion production of a Higgs boson in models with massive color-octet scalars in the ${\bf (8,1)_0}$ representation using an effective-theory approach. We derive a compact analytic expression for the relevant Wilson coefficient, and explain an interesting technical aspect of the calculation that requires inclusion of the quartic-scalar interactions at next-to-next-to-leading order. We perform a renormalization-group analysis of the scalar couplings to derive the allowed regions of parameter space, and present phenomenolo…
Using the full statistics of the DELPHI experiment at $\sqrt{s}=91 GeV$ 3-jet events are selected and gluon respectively quark jet enriched subsamples are defined. The leading systems of the two kinds of jets are determined using rapidity gaps. The sum of charges of the leading systems is studied. It is found that for gluon-jets there is a significant excess of leading systems with total charge zero when compared to Monte Carlo simulations with JETSET. The corresponding leading systems of quark-jets do not exhibit such an excess. The mass spectra of the leading systems with total charge zero a…
We extract constraints on the parameter space of the MW model by comparing the cross-sections for dijet, top-pair, dijet-pair, $t\bar t t \bar t$ and $b\bar b b \bar b$ productions at the LHC with the strongest available experimental limits from ATLAS or CMS at 8 or 13 TeV. Overall we find that masses below 1 TeV have not been excluded for color octet scalars as it is often claimed in the literature. The constraints that can be placed on coupling constants are typically weaker than those from existing theoretical considerations, with the exception of the parameter $η_D$.
The scalar color octet contribution to the resonance $t\bar{t}$-pair production at the LHC is calculated and analysed with account of the one loop effective two gluon vertex. It is shown that this contribution from the scalar color octet $F_2$ predicted by the minimal model with the four color quark-lepton symmetry is for $\sqrt{s}=13$ TeV of about a few percents for $750 < m_{F_2} < 1800$ GeV and can exceed 10% for $400 < m_{F_2} < 750$ GeV. It is also pointed out that the search for the scalar octet $F_2$ as the resonance in the dijet mass spectra seems to be difficult because of the smallne…
We propose that the possible 750 GeV diphoton excess can be explained in the color-octet neutrino mass model extended with a scalar singlet $Φ$. The model generally contains $N_s$ species of color-octet, electroweak doublet scalars $S$ and $N_f$ species of color-octet, electroweak triplet $χ$ or singlet $ρ$ fermions. While both scalars and fermions contribute to the production of $Φ$ through gluon fusion, only the charged members induce the diphoton decay of $Φ$. The diphoton rate can be significantly enhanced due to interference between the scalar and fermion loops. We show that the diphoton …
Many new-physics models, especially those with a color-triplet top-quark partner, contain a heavy color-octet state. The "naturalness" argument for a light Higgs boson requires that the color-octet state be not much heavier than a TeV, and thus it can be pair-produced with large cross sections at high-energy hadron colliders. It may decay preferentially to a top quark plus a top-partner, which subsequently decays to a top quark plus a color-singlet state. This singlet can serve as a WIMP dark-matter candidate. Such decay chains lead to a spectacular signal of four top quarks plus missing energ…
The Color-Octet Model has been used successfully to analyze many problems in heavy quarkonium production. We examine some of the conceptual and practical problems of the soft gluon emission process in the Color-Octet Model. We use a potential model to describe the initial and final states in the soft gluon emission process, as the emission occurs at a late stage after the production of the heavy quark pair. It is found in this model that the soft gluon M1 transition, 1S0(8)->3S1(1), dominates over the E1 transition, 3PJ(8)->3S1(1), for J/psi and psi' production. Such a dominance may help resol…
We study the properties and production mechanisms of color-octet scalars at the LHC. We focus on the single production of both charged and neutral members of an (8,2)_1/2 doublet through bottom quark initial states. These channels provide a window to the underlying Yukawa structure of the scalar sector. Color-octet scalars naturally appear in grand unified theories based on the SU(5) gauge symmetry. In the context of adjoint SU(5) these fields are expected to be light to satisfy constraints coming from unification and proton decay, and may have TeV-scale masses. One combination of their coupli…
Color-octet contributions to the associate J/psi+gamma hadroproduction are studied in detail, and found to be negligible, compared to the ordinary color-singlet contribution. Within the color-singlet model the J/psi+gamma production in the leading order is possible only through gluon-gluon fusion process. Therefore, the associate J/psi+gamma hadroproduction remains to be useful as a clean channel to probe the gluon distribution inside proton, to study heavy quarkonia production mechanism, and to find proton's spin structure.
We consider the phenomenology of CP violation in a color-octet extended scalar sector for t\bar{t} production and decay at the LHC. In particular we study the effect of the two neutral color-octet scalars S_I and S_R that occur in the model. There are two new sources of CP violation: a phase in the couplings of S_{I,R} to top-quarks; and two phases in the quartic couplings of the scalar potential. In resonant production of a single S_{I,R} followed by its decay into t\bar{t} pairs through the parton level process gg to S_{I,R} to t\bar{t}, we find large raw CP asymmetries which can reach 12%. …
We present a calculation of the leading order QCD fragmentation functions for gluons to split into spin-triplet D-wave quarkonia. We apply them to evaluate the gluon fragmentation contributions to inclusive ^3D_J quarkonium production at large transverse momentum processes like the Tevatron and find that the D-wave quarkonia, especially the charmonium 2^{--} state, could be observed through color-octet mechanism with present luminosity. Since there are distinctively large gaps between the contributions of two different (i.e, color-singlet and color-octet) quarkonium production mechanisms, our …
It has recently been suggested that gauge invariance forbids the coupling of a massive color-octet vector meson to two gluons. While this is true for operators in an effective Lagrangian of dimension four or less, we demonstrate that dimension six interactions will lead to such couplings. In the case of technicolor, the result is a technirho-gluon-gluon coupling comparable to the naive vector meson dominance estimate, but with a substantial uncertainty. This has implications for several recent studies of technicolor phenomenology.
We show that the usual vector meson dominance method does not apply directly to the mixing of a color-octet vector boson (color-octet technirho) with the gluon because of gauge invariance. We propose a gauge invariant method where one works in a physical basis with mass eigenstate fields. As a result, we show that the physical technirho does not couple to two gluons, contrary to the general belief. Consequences for the production of a pair of color-octet, isosinglet technipions (technietas) at Fermilab is analysed by means of a simulation of the signal and background, including kinematical cut…
Colored dark sectors where the dark matter particle is accompanied by colored partners have recently attracted theoretical and phenomenological interest. We explore the possibility that the dark sector consists of the dark matter particle and a color-octet partner, where the interaction with the Standard Model is governed by an effective operator involving gluons. The resulting interactions resemble the color analogues of electric and magnetic dipole moments. Although many phenomenological features of this kind of model only depend on the group representation of the partner under SU(3)$_c$, we…
Color-octet scalars, if present at the TeV scale, will be produced in abundance at the LHC. We discuss in some detail the phenomenology of scalars in the (8,2)_{1/2} representation, recently identified by Manohar and Wise as an addition to the standard-model Higgs sector consistent with the principle of minimal flavor violation. Couplings of this multiplet to the Higgs lift the mass degeneracy among its states, possibly allowing for two-body decays of a heavier colored scalar to a lighter one and a gauge boson. We perform a renormalization group analysis of these couplings and find that limits…
We present one loop results for the amplitudes giving rise to couplings between a color octet scalar, a gluon, and an electroweak gauge boson. These amplitudes could signal new physics in $γ$ jet, $Z$ jet and $W$ jet production at the LHC. We compute the relevant branching ratios and identify regions of parameter space where these decay modes become important. This can happen for scalar masses below the threshold for decay into heavy quark pairs ($t\bar t$ and $t\bar b$); or for small Yukawa couplings in which case the colored scalars are fermiophobic. In the case of light scalars, ${\cal B}(S…
We investigate $J/ψ$ photoproduction asymmetries in the framework of the NRQCD factorization approach. It is shown that the color octet contribution leads to large uncertainties in the predicted asymmetries which rules out the possibility to precisely measure the gluon polarization in the nucleon through this final state. For small values of the color octet parameters being compatible with $J/ψ$ photoproduction data it appears possible that a measurement of $J/ψ$ asymmetries could provide a new test for the NRQCD factorization approach, on one hand, or a measurement of the polarized gluon dist…
We discuss the phenomenology of colour scalar octets. Namely, we consider the discovery potential of scalar octets at LEP, FNAL and LHC. Scalar octets decay mainly into two gluons and new hadrons composed from scalar colour octets are rather long lived $(Γ\leq O(10)Kev)$. For the scalar octet masses $M \geq O(50)Gev$ scalar octets producing at FNAL or LHC decay into two gluons that leads to additional four-jet events. We propose to look for scalar octets by the measurement of the distributions of differential cross sections on the invariant di-jet masses. Scalar octets naturally arise in model…
Heavy colored scalar particles appear in a variety of new physics (NP) models and could be produced at the Large Hadron Collider (LHC). Knowing the total production cross section is important for searching for these states and establishing bounds on their masses and couplings. Using soft-collinear effective theory, we derive a factorization theorem for the process $pp\to SX$, where $S$ is a color-octet scalar, that is applicable to any NP model provided the dominant production mechanism is gluon-gluon fusion. The factorized result for the inclusive cross section is similar to that for the Stan…
We investigate $J/ψ$ photoproduction asymmetries in the framework of the NRQCD factorization approach. It is shown that the color octet contribution leads to large uncertainties in the predicted asymmetries which rules out the possibility to precisely measure the gluon polarization in the nucleon through this final state. For small values of the color octet parameters being compatible with $J/ψ$ photoproduction data it appears possible that a measurement of $J/ψ$ asymmetries could provide a new test for the NRQCD factorization approach, on one hand, or a measurement of the polarized gluon dist…
We use the NRQCD factorization formalism to calculate the relativistic corrections to the fragmentation function for a gluon fragmenting into a spin-triplet S-wave heavy quarkonium. We make use of the gauge-invariant formulation of the fragmentation function of Collins and Soper. The color-octet contribution receives a large, negative relativistic correction, while the color-singlet contribution receives a large, positive relativistic correction. The considerable decrease in the color-octet contribution requires a corresponding increase in the phenomenological value of the leading color-octet …
We present a phenomenological theory of scalar particles that transform as a sextet and an octet of QCD interactions. These particles may arise as light bound states of a fundamental dynamics giving rise to a composite Higgs boson and partial compositeness for the top. As a concrete example, we discuss an explicit UV completion based on the SU(4)/Sp(4) coset, where QCD colour is carried by additional fundamental fermions charged under the confining gauge group. Top partners, as well as potentially even lighter coloured scalars, arise as bound states of the coloured fermions. We study productio…
Although the Higgs boson mass and single production rate have been determined more or less precisely, its other properties may deviate significantly from its predictions in the standard model (SM) due to the uncertainty of Higgs data. In this work we study the Higgs pair production at the LHC in the Manohar-Wise model, which extends the SM by one family of color-octet and isospin-doublet scalars. We first scanned over the parameter space of the Manohar-Wise model considering exprimental constraints and performed fits in the model to the latest Higgs data by using the ATLAS and CMS data separat…
Inclusive bottomonium hadroproduction at the Tevatron is firstly examined in a Monte Carlo framework with the colour-octet mechanism implemented in the event generation. We extract some NRQCD colour-octet matrix elements relevant for $Υ(1S)$ hadroproduction. Remarkably we find a quite small contribution (compatible with zero) from feeddown of $χ_{bJ}$ states produced through the colour-octet mechanism: $Υ(1S)$ indirect production via $χ_{bJ}$ decays should be mainly ascribed to the colour-singlet model. Finally we extrapolate to LHC energies to predict prompt $Υ(1S)$ production rates.
The observation of unpolarized quarkonium production in high energy pp collisions, at mid rapidity, implies a significant violation of the non-relativistic QCD (NRQCD) velocity scaling rules. A precise experimental confirmation of this picture could definitely rule out the current formulation of the factorization expansion. This conclusion relies on current perturbative determinations of the short-distance kinematic factors and may be reverted if improved calculations would modify, in a very specific way, their transverse momentum dependences. That solution would result, however, in a full deg…
Recently we have proved NRQCD color octet factorization of S-wave and P-wave heavy quarkonia production at all orders in coupling constant in QCD in vacuum at high energy colliders in Eur. Phys. J. C76 (2016) 448 and in arXiv:1807.04722 [hep-ph] respectively. In this paper we extend this to prove NRQCD color octet factorization of P-wave heavy quarkonium production in non-equilibrium QCD at RHIC and LHC at all orders in coupling constant. This proof is necessary to study the quark-gluon plasma at RHIC and LHC.
The remarkable discrepancy between theory and data on the p_t distribution of J/psi polarization in the process pp -> J/psi+X has been standing as a puzzle for a long time. Our early work indicates that if only considering the color-singlet state, NLO corrections may drastically change the distribution, but are not sufficient to accommodate the data. The color-octet intermediate state was suggested to make up the gap. Therefore a direct motivation is to evaluate if the NLO corrections to the J/psi production via a color-octet can indeed remedy the problem. Unfortunately, our results show that …
In order to get information about the polarized gluon distribution in a proton, we studied the electroproduction of ψ' in polarized electron and polarized proton collisions in the framework of the NRQCD factorization approach. The value of the cross section dΔσ/ dp_T^2 for color-octet mechanism is about 5 times larger than that for color-singlet one, and it might be another test of the color-octet model if the polarized gluon distribution Δg(x) is well known. Furthermore, we found that this reaction is quite effective for testing the model of gluon polarization by measuring the double spin asy…
Gluon fragmentation represents the dominant source of high energy prompt quarkonia at hadron colliders. Fragmentation approximations break down, however, when a quarkonium's transverse momentum becomes comparable to its mass. In this paper, we identify a large class of color-octet diagrams that mediate quarkonia production at all energies and reduce to the dominant set of gluon fragmentation graphs in the high $p_\perp$ limit. They contribute to quarkonia differential cross sections at the same order as color-singlet diagrams and bring theoretical predictions for Upsilon and Psi production at …
We study $c \bar c$ color-octet contribution to $B\to ψ(ψ') X$. When this contribution is included, the theoretical predictions for the branching ratios become in much better agreement with the experiment. This mechanism also enhances the partial rate asymmetries by about a factor of five. The inclusive $ψ(ψ')$ resulting from $b\to d+{}$gluon can have asymmetry around a few percent whereas those from $b\to s+{}$gluon has it around $4\times 10^{-4}$. The asymmetry in the former modes should be observable, to a significance of $3σ$, with about $(1-10)\times 10^8B$ mesons.
In this paper the twist-3 distribution amplitude of the quark-antiquark-gluon Fock state in the η_c meson is studied. To calculate the moments of this distribution amplitude QCD sum rules is applied. Using the results of the calculation the model of this distribution amplitude is built. In addition NRQCD matrix elements which determine the properties of the quark-antiquark-gluon Fock state are determined. In particular, the probability amplitude to find the quark-antiquark pair in the color octet state, the mean gluon energy and the fraction of momentum carried by gluon, the relative velocity …
We investigate the interaction between a heavy quark-antiquark pair in color octet configuration in gluon plasma. We calculate nonperturbatively an effective thermal potential for such a pair through the study of the correlation function of a hybrid state with $Q \bar{Q}$ octet and an adjoint gluon source in the static limit. We discuss the extraction of an octet potential, and present results for the effective thermal potential between octet $Q \bar{Q}$ pair in gluon plasma for moderately high temperatures $\lesssim 2 T_c$. The implications of our result are discussed.
Higgs pair production is studied in the extension of the Standard Model by color octet scalar and vector particles in TeV mass range for the LHC. The relevant parameters are their masses and portal couplings to the Higgs boson.The rate is enhanced considerably in some parts of the parameter space compared to the SM which are allowed by the latest measured bounds on the Higgs decay to $ZZ^*$. The model will be tested experimentally at the upcoming LHC run.
We discuss the production of heavy colored paricles at the Large Hadron Collider (LHC) through gluon-gluon fusion process. A factorization theorem is obtained for this process using Soft Collinear Effective Theory. Our factorization theorem does not depend on any assumptions regarding the physics above the mass of the heavy colored particle. In this sense it is universal. The matching coefficient at the heavy particle mass scale depends however on the unkown physics above that scale and thus it is model dependent. Due to the large mass of the heavy colored particle, i.e., the hard scale and ne…
This paper completes the study of the next-to-leading order (NLO) QCD corrections to massive color-octet vector boson production at the LHC and Tevatron. The massive color-octet vector bosons are generically referred to as colorons. Building on our previous calculation of quark-initiated coloron production at NLO, we use the pinch technique to investigate coloron production via gluon fusion. We demonstrate that this one-loop production amplitude is finite, and find that its numerical contribution to coloron production is typically four orders of magnitude smaller than the contribution from qua…
We explore the phenomenology of scalar fields in the adjoint representation of SM gauge groups. We write a general set of dimension 5 effective operators in which SM adjoint scalars couple to pairs of standard model bosons. Using these effective operators, we explore new possible decay channels of a scalar color octet into a gluon and a Z boson/ gluon and a photon. We recast several analyses from Run I of the LHC to find constraints on an a scalar octet decaying into these channels, and we project the discovery potential of color octets in our gluon+photon channel for the 14 TeV run of LHC.
We consider new physics contributions to the top-quark forward-backward asymmetry from a neutral $V^0_8$ or charged $V^+_8$ color-octet vector exchanged in the $t$-channel. We study the phenomenological constraints on these particles arising from the Tevatron and LHC7 measurements and compare them with those on their color singlet counterparts $Z^\prime$ and $W^\prime$. We find that the color octets fare better than the singlets in that they generate a lower $A_C$, a lower high-invariant mass cross-section at LHC7 and a lower same sign top-pair cross-section. However, they also generate a lowe…
We compute the one-loop contributions from a color octet scalar to the tensor anomalous couplings of top and bottom quarks to gluons, photons and W bosons. We use known constraints on the parameters of the model to compare the predicted size of these couplings with existing phenomenological constraints.
The excess in top quark forward-backward asymmetry has been a hot topic in recent years. Although there are many proposals to explain it, most of them can not fit the differential distributions well. The color octet axial-vector like particle, with mass near the top quark pair threshold, is still a good description of the differential distributions. We study how to distinguish the color singlet and octet mediating particles in top quark pair production by adopting the color flow method. For the first time, we show that such a proposal for the froward-backward asymmetry can be cross-checked ind…
We consider the contribution of new strongly interacting sector, with a characteristic scale of half a TeV, to top quark production at the Tevatron. The color-octet, isosinglet analog of the $ρ$ meson in this theory is produced copiously in hadron colliders. If the mass of this resonance is less than twice the mass of the lightest pseudo-Goldstone bosons, then an important decay mode could be to the color-octet analog of the $η$ and a gluon. The subsequent decay of this $η$ into $\ttbar$ gives rise to top quark events with a hard gluon.
We propose the color-octet mechanism combined with the two gluon exchange model for the diffractive $J/ψ$ production in hadron collisions. In the leading logarithmic approximation (LLA) in QCD, we find that the diffractive $J/ψ$ production rate is related to the off-diagonal gluon density in the proton and to the nonperturbative color-octet matrix element of $J/ψ$. The rate is found to be very sensitive to the gluon density at very small values of $x$ (down to $x=O(10^{-6})$). As a result, this process may provide a wide window for testing the two-gluon exchange model, and may be particularly …
We re-analyze Tavatron data on charmonium hadroproduction in the framework of the color-octet model implemented in the event generator PYTHIA taking into account initial-state radiation of gluons and Altarelli-Parisi evolution of final-state gluons fragmenting into $c\bar{c}$ pairs. We obtain new values for the color-octet matrix elements relevant to this production process. We discuss the sensitivity of our results to the transverse momentum lower cut-off employed in the generation to avoid the problematic $p_t{\to}0$ region, arguing about the reliability of our previous extraction of the NRQ…
Recently has been shown that the physical (mass eigenstate) color-octet technirho does not couple to two gluons. In this letter we study how this result affects the presently accepted limits for the color-octet technirho mass obtained from the study of dijets production at the Tevatron. First we show that data from Tevatron Run 1b can not exclude any mass range. Finally, we obtain limits for the Tevatron Run II.
We consider the contribution of new strongly interacting sector, with a characteristic scale of half a TeV, to top quark production at the Tevatron. The color-octet, isosinglet analog of the $ρ$ meson in this theory is produced copiously in hadron colliders. If the mass of this resonance is less than twice the mass of the lightest pseudo-Goldstone bosons, then an important decay mode could be to the color-octet analog of the $η$ and a gluon. The subsequent decay of this $η$ into $\ttbar$ gives rise to top quark events with a hard gluon.
We report the first complete calculation of QCD corrections to the production of a massive color-octet vector boson. Our next-to-leading-order (NLO) calculation includes both virtual corrections as well as corrections arising from the emission of gluons and light quarks, and we demonstrate the reduction in factorization-scale dependence relative to the leading-order approximation used in previous hadron collider studies. We show that the QCD NLO corrections to coloron production are as large as 30%, and that the residual factorization scale-dependence is reduced to of order 2%. We also calcula…
The NLO QCD corrections to Upsilon production via S-wave color-octet states Upsilon(^1S_0^8,^3S_1^8) at the Tevatron and LHC is calculated. The K factors of total cross section (ratio of NLO to LO) are 1.313 and 1.379 for Upsilon(^1S_0^8) and Upsilon(^3S_1^8) at the Tevatron, while at the LHC they are 1.044 and 1.182, respectively. By fitting the experimental data from the D0, the matrix elements for S-wave color-octet states are obtained. And new predictions for Upsilon production are presented. The prediction for the polarization of inclusive Upsilon contains large uncertainty rising from th…
The LHC is now studying in detail the couplings of the Higgs boson in order to determine if there is new physics. Many recent studies have examined the available fits to Higgs couplings from the perspective of constraining two Higgs doublet models (2HDM). In this paper we extend those studies to include constraints on the one loop couplings of the Higgs to gluons and photons. These couplings are particularly sensitive to the existence of new colored particles that are hard to detect otherwise and we use them to constrain a 2HDM augmented with a color-octet scalar, a possibility motivated by mi…
We study and constrain the parameter space of the vector color-octet model from observed data at Tevatron by studying top quark pair production and associated observables afbt and spin-correlation. In particular we study invariant mass and rapidity dependence of afbt at Tevatron. In addition to FC couplings we extend our study to include FV coupling involving first & third generation quarks for both these processes. In order to ensure that we remain within the constraints imposed by LHC data, we analyze the charge asymmetry, p_T spectrum & invariant mass in t\bar t production data at LHC. The …
