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1.
In the framework of the topcolor-assisted technicolor (TC2) model, we study the production of the neutral top-pion πt0 in association with a high-pT jet al the LHC, which proceeds via the partonic processes gg→πt0g, gq→πt0q, qq→πt0g, gb(b)→πt0b(b), and bb→πt0g. We find that it is very challenging to detect the neutral top-pion πt0 via the process pp→πt0 +jet-t-X→tt +jet + X, while the possible signatures of πt0 might be detected via the process pp→πt0 +jet+X→(tc+tc)+jet+X at the LHC. 相似文献
2.
In the framework of topcolor-assisted technicolor (TC2) theory, we study a flavor changing single top quarkproduction process pp(pp) →Ⅱ0t → tc(tc) at upgraded Tevatron and LHC. The results show that with the flavor changingcoupling of neutral toppion to top and charm quark, toppion provides a large te-channel resonance effect. The signal ofsingle top production could be detected at LHC. Otherwise, the narrow peak in the invariant mass distribution could beclearly detected both at upgraded Tevatron and LHC. Therefore, such single top production process provides a uniqueway to test TC2 model via the detection of tc-channel neutral toppion contribution. 相似文献
3.
In the context of the top-color-assisted technicolor (TC2) model, the flavor-changing neutral-current (FCNC) interaction induced by the top-higgs (h0t) are predicted at tree level. We study the relevant processes of e+e-(γγ)→ t\bar{c}h0t at the International Linear Collider (ILC). It is found that these rare processes production rates can be enhanced significantly in the TC2 model. Especially for the process γγ → t\bar{c}h0t, the total cross section will reach a few fb in the reasonable parameter space. We also calculate the distributions of transverse momenta, pseudo-rapid and invariant mass of the top-higgs. In view of the main decay modes of top-higgs for mh0t<2mt, we find that there will be several hundreds FCNC events produced at the ILC with annuallyintegral luminosity of 500 fb-1. Due to the clean background, such FCNC signals can possibly be detected at the ILC. 相似文献
4.
In the context of the topcolor-assisted technicolor (TC2) model, we consider the production of the neutral scalar S(πt0 or ht0) associated with a photon at the LHC and compare our results with those given by the minimal supersymmetric extension of the Standard Model (MSSM). We find that its production cross section is larger or smaller than that of the scalar particle predicted by the MSSM model, depending on the values of the relevant free parameters. 相似文献
5.
Jin Min Yang 《Annals of Physics》2005,316(2):529-539
We briefly review the studies on the top quark FCNC processes at a next-generation linear collider. Such processes, including various FCNC top quark rare decays and top-charm associated productions, are extremely suppressed in the standard model (SM) but could be significantly enhanced in some extensions. We compared the predictions from different typical new physics models: the SM, the minimal supersymmetric model (MSSM), the general two-higgs-doublet model (2HDM), and the topcolor-assisted technicolor (TC2) model. Our conclusion is: (1) While all the new physics models can enhance the rates by several orders relative to the SM predictions, the TC2 model predicts much larger rates than other models; (2) The optimal channel for probing the top quark FCNC is the top-charm associated production in γγ collision, which occurs at a much higher rate than e+e− or e−γ collision and can reach the detectable level for a large part of the parameter space. 相似文献
6.
We consider the rare top quark decays in the framework of topcolorassisted technicolor (TC2) model. We find that the contributions of top-pions and top-Higgs predicted by the TC2 model can enhance the SM branching ratios by as much as 6—9 orders of magnitude. i.e., in the most case, the orders of magnitude of branching ratios are Br(t→cg)~10-5, Br(t→cZ)~10-5, Br(t→cγ)~10-7. With the reasonable values of the parameters in TC2 model, such rare top quark decays may be testable in the future experiments. So, rare top quark decays provide us a unique way to test TC2 model. 相似文献
7.
Production of a neutral scalar associatedwith a photon at the LHC in the topcolor-assisted technicolor model
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In the context of the topcolor-assisted technicolor (TC2) model, we consider the production of the neutral scalar S(πt0 or ht0) associated with a photon at the LHC and compare our results with those given by the minimal supersymmetric extension of the Standard Model (MSSM). We find that its production cross section is larger or smaller than that of the scalar particle predicted by the MSSM model, depending on the values of the relevant free parameters. 相似文献
8.
O. ?ak?r I. T. ?ak?r A. Senol A. T. Tasci 《The European Physical Journal C - Particles and Fields》2010,70(1-2):295-303
The top quark is the heaviest particle to date discovered, with a mass close to the electroweak symmetry breaking scale. It is expected that the top quark would be sensitive to the new physics at the TeV scale. One of the most important aspects of the top quark physics can be the investigation of the possible anomalous couplings. Here, we study the top quark flavor changing neutral current (FCNC) couplings via the extra gauge boson Z′ at the Large Hadron Collider (LHC) and the Compact Linear Collider (CLIC) energies. We calculate the total cross sections for the signal and the corresponding Standard Model (SM) background processes. For an FCNC mixing parameter x=0.2 and the sequential Z′ mass of 1 TeV, we find the single top quark FCNC production cross sections 0.38(1.76) fb at the LHC with $\sqrt{s_{pp}}=7(14)$ TeV, respectively. For the resonance production of sequential Z′ boson and decays to single top quark at the Compact Linear Collider (CLIC) energies, including the initial state radiation and beamstrahlung effects, we find the cross section to be 27.96(0.91) fb at $\sqrt{s_{e^{+}e^{-}}}=1(3)$ TeV, respectively. We make the analysis to investigate the parameter space (mixing-mass) through various Z′ models. It is shown that the results benefit from the flavor tagging. 相似文献
9.
We study the one-loop contribution of the effective flavor changing neutral couplings (FCNC) tcZ on the charm quark electric dipole moment. Using the known limits on the top and charm quarks electric dipole moments, we place limits on these FCNC anomalous couplings. 相似文献
10.
Induced flavour-changing neutral currents (FCNC) in supersymmetric unified theories are investigated both in models with the standard SU(2)L × U(1) gauge symmetry and in models with an extra ?(1) gauge symmetry. Supersymmetric extension of the natural flavour conservation laws for neutral currents is obtained by adding a condition regarding the assumed type of supersymmetry breaking. This condition ensures no direct flavour-changing couplings of neutral gauge-Higgs fermions and at the same time is necessary and sufficient for the natural suppression of the induced FCNC. It is found that in the class of models satisfying the new condition the contribution of the scalar partners of quarks to the induced strangeness-changing neutral current is comparable to that of the quarks in , while it is negligibly small in KL ? KS mass difference. 相似文献
11.
M. Khatiri Yanehsari S. Jafari M. Mohammadi Najafabadi 《International Journal of Theoretical Physics》2013,52(11):4229-4236
We study the possibility of production of same sign top quark pairs at the LHC as a direct probe of flavor changing neutral current (FCNC) processes in the tqg vertices. In particular, the LHC potential to probe the flavor violating parameter κ/Λ is investigated with 5, 10, 15, and 20 fb?1 of integrated luminosity of data of 7 and 8 TeV collisions. We find that the LHC can probe it down to 0.13 TeV?1 via double top production process. Also, we examine the effects of variation of factorization scale and different parton distribution functions on the total cross section of same sign top quark pair at the LHC. The results could be a valid starting point for a more detailed experimental study. 相似文献
12.
HOU Hong-Sheng 《理论物理通讯》2009,52(6):1036-1040
We studied the charged top-pion in the topcolor assisted technicolor model (TC2). If the charged top-pions are heavy, mπt >mt+mb, they will decay mainly via the channel π+t → t \bar{b}. We also calculated the production ofcharged top-pion at the Tevatron and LHC. The cross section can reach to 100 fb at the Tevatron and dozens of pb at the LHC depending on the mass of the top-pion. 相似文献
13.
H.Nakazawa 《中国物理C(英文版)》2010,34(6):801-806
We review recent measurements of pure neutral final state production in the two-photon processes,γγ→π0π0 and ηπ0 at the Belle experiment.In the lower invariant mass region,properties of light scalar mesons are measured by partial wave analysis.In the higher energy region the total and differential cross section are compared with QCD models. 相似文献
14.
In the context of topcolor-assisted techicolor (TC2)model, we study the contributions of the neutral top-pion π0t to the lepton flavor violation (LFV) processes li→ljγ,li→ljlkll and t→clilj respectively. We find that the present experimental upper bound for μ→eγ gives severe constraints on the free parameters of the TC2 model. Under these constraints,we consider the processes li→ljlkll and t→c lilj generated by π0t exchange at the tree-level and the one loop level. Our numerical results show that the neutral top-pion π0t can enhance the branching ratios of these processes by several orders of magnitude. Some of those processes might be used to detect the possible signals of π0t in the futrue high energy experiment. 相似文献
15.
XU Wen-Na WANG Xue-Lei XIAO Zhen-Jun 《理论物理通讯》2008,49(1):193-198
In the framework of topcolor-assisted technicolor (TC2) model, there exist tree-level flavor-changing (FC) couplings, which can result in the loop-level FC coupling tcg. Such tcg coupling can contribute significant clues at the forthcoming Large Hadron Collider (LHC) experiments. In this paper, based on the TC2 model, we study some single t-quark production processes involving tcg coupling at the Tevatron and LHC: pp(pp) → tq (q = u, d, s), tg. We calculate the cross sections of these processes. The results show that the cross sections at the Tevatron are too small to observe the signal, but at the LHC it can reach a few pb. With the high luminosity, the LHC has considerable capability to find the single t-quark signal produced via some FC processes involving coupling tcg. On the other hand, these processes can also provide some valuable information of the coupling tcg with detailed study of the processes and furthermore provide the reliable evidence to test the TC2 model 相似文献
16.
LIU Yao-Bei SHEN Jie-Fen CUI Xiao-Min REN Xiao-Yan 《理论物理通讯》2008,49(5):1279-1282
The littlest Higgs (LH) model is the most economical one among various little Higgs models, which predicts the existence of the charged scalars Φ^±. In this paper, we study the production of the charged Higgs boson Φ^- with single top quark via the process gb →tΦ^- at the CERN Large Hadron Collider (LHC). The numerical results show that the production cross section is sma/ler than 0.2 pb in most of the parameters space, it is very difficult to observe the signatures of the charged scalars via the process pp → gb + X → tΦ^- + X at the LHC experiments. However, it can open a window to distinguish the top-pions in the TC2 model or charged Higgs in the MSSM from Φ^±. 相似文献
17.
《Nuclear Physics B》2001,600(1):21-38
Decays of the top quark induced by flavor changing neutral currents (FCNC) are known to be extremely rare events within the Standard Model. This is so not only for the decay modes into gauge bosons, but most notably in the case of the Higgs channels, e.g., t→HSM+c, with a branching fraction of 10−13 at most. Therefore, detection of FCNC top quark decays in a future high-energy, and high-luminosity, machine like the LHC or the LC would be an indisputable signal of new physics. In this paper we show that within the simplest extension of the SM, namely the general two-Higgs-doublet model, the FCNC top quark decays into Higgs bosons, t→(h0,H0,A0)+c, can be the most favored FCNC modes — comparable or even more efficient than the gluon channel t→g+c. In both cases the optimal results are obtained for Type II models. However, only the Higgs channels can have rates reaching the detectable level (10−5), with a maximum of order 10−4 which is compatible with the charged Higgs bounds from radiative B-meson decays. We compare with the previous results obtained in the Higgs sector of the MSSM. 相似文献
18.
Wenna Xu Xuelei Wang Zhen-jun Xiao 《The European Physical Journal C - Particles and Fields》2007,51(4):891-897
In the topcolor-assisted technicolor (TC2) model, the typical physical particles, top-pions and top-Higgs, are predicted and
the existence of these particles could be regarded as robust evidence for the model. These particles are accessible at the
Tevatron and LHC, and furthermore the flavor-changing (FC) feature of the TC2 model may provide us with a unique opportunity
to probe them. In this paper, we study some interesting FC production processes of top-pions and top-Higgs particles at the
Tevatron and LHC, i.e., cΠt
- and cΠt
0(ht
0) productions. We find that the light charged top-pions are not favorable by the Tevatron experiments, and the Tevatron has
little capability to probe the neutral top-pion and top-Higgs particles via these FC production processes. At LHC, however,
the cross section can reach the level of 10–100 pb for cΠt
- production and 10–100 fb for cΠt
0(ht
0) production. So one can expect that enough signals could be produced at the LHC experiments. Furthermore, the SM backgrounds
should be clean due to the FC feature of the processes, and the FC decay modes Πt
-→bc̄, Πt
0(ht
0)→tc̄ can provide us with the signal typical for the detection of the top-pions and top-Higgs particles. Therefore, one may
have hope to find the signal of top-pions and top-Higgs particles with the running of LHC via these FC processes.
PACS 12.60.Nz; 14.80.Mz; 12.15.LK; 14.65.Ha 相似文献
19.
J. Carvalho N. Castro L. Chikovani T. Djobava J. Dodd S. McGrath A. Onofre J. Parsons F. Veloso The ATLAS Collaboration 《The European Physical Journal C - Particles and Fields》2007,52(4):999-1019
The ATLAS experiment sensitivity to top quark flavour changing neutral current (FCNC) decays was studied at LHC using tt̄
events. While one of the top quarks is expected to follow the dominant Standard Model decay t→bW, the other decays through
a FCNC channel, i.e. t→Zu(c), t→γu(c) or t→gu(c). Different types of analyses, applied to each FCNC decay mode, were compared.
The FCNC branching ratio sensitivity (assuming a 5σ signal significance) and 95% confidence level limits on the branching
ratios (in the hypothesis of signal absence) were obtained. 相似文献
20.
Inclusive eta production at hadron colliders is considered, based on the evaluation of the eta fragmentation functions at next to leading order. Absolute predictions at LHC and SSC are presented, including the ratio η/π0, together with the estimate of the theoretical uncertainty, as a possible neutral background to theH→γγ detection. 相似文献