Tensor Unparticles Research Articles

Higgs to Diphoton Decay Rate and the Antisymmetric Tensor Unparticle Mediation

We study the contribution of the antisymmetric tensor unparticle mediation to the diphoton production rate of the Higgs boson and try to explain the discrepancy between the measured value of the decay width of the discovered new resonance and that of the standard model Higgs boson. We observe that tree level contribution of the antisymmetric unparticle mediation is a possible candidate to explain the measured value of the diphoton decay rate.

Constraining unparticles from top physics at the Tevatron

We study and analyze the recent observations of the top pair production $\sigma (p\bar p\to t \bar t)$ at TeVatron through flavor conserving and flavor violating channels ${\it via}$ vector and tensor unparticles. The unparticle sector is considered with the possibility of being a color singlet or octet. The modified unparticle propagator is used to investigate the contribution of these unparticles to the observed $A_{FB}^{t\bar t}$ (forward backward asymmetry in top pair production) and the spin correlation at TeVatron. We have also studied the impact of the flavor violating couplings of unparticles to the third generation quarks on (a) pair production of same sign tops/antitops $\sigma (p\bar p\to tt+\bar t \bar t)$ at TeVatron and (b) the partial top decay width for $\Gamma_{\cal U}(t\to u\,{\cal U}^V)$. We find that a large region of parameter space is consistent with the measurements of \tt production cross-section, \afbt and spin correlation coefficient at TeVatron and observe that the top decay width measurement constrains the flavor violating coupling of vector unparticles more severely than the same sign top/antitop production at TeVatron. We also predict the best point-set in the model parameter space for specific choices of \du corresponding to $\chi^2_{\rm min}$ evaluated using the \mttb spectrum of \afbt from the data set of Run II of TeVatron at the integrated luminosity 8.7 fb$^{-1}$. Our results and analysis are consistent even with unparticle theories having broken scale invariance as long as the infrared cut-off scale is much less than the top pair production threshold.

ANTISYMMETRIC TENSOR UNPARTICLE AND THE RADIATIVE LEPTON FLAVOR VIOLATING DECAYS

We study the contribution of the antisymmetric tensor unparticle mediation to the branching ratios of the radiative lepton flavor violating decays and predict a restriction region for free parameters of the scenario by using experimental upper limits. We observe that the branching ratios of the radiative lepton flavor violating decays are sensitive to the fundamental mass scales of the scenario and to the scale dimension of antisymmetric tensor unparticle. We obtain a more restricted set for the free parameters in the case of the μ→e γ decay.

Quasinormal modes of unparticle black holes

In the background of unparticle-enhanced black hole geometry, we provide the quasinormal modes of scalar, vector, and Dirac particles around it. Ungravity by tensor unparticles contributes positively to the Newtonian gravity and black holes can be formed at the LHC without any extra dimensions. In the ungravity-dominant regime, the gravity looks much like that of the Schwarzschild geometry in fractional number of extra dimensions. We argue in this analysis that quasinormal modes are good fingerprints to distinguish ungravity from extra dimensions, by showing that the unitarity constraints on ungravity forbid some of the quasinormal modes which are allowed in extra dimensions.

The effect of antisymmetric tensor unparticle mediation on the charged lepton electric dipole moment

We study the contribution of antisymmetric tensor unparticle mediation to the charged lepton electric dipole moments and restrict the free parameters of the model by using the experimental upper bounds. We observe that the charged lepton electric dipole moments are strongly sensitive to the scaling dimension dU and the fundamental scales MU and ΛU. The experimental current limits of electric dipole moments are reached for the small values of the scaling dimension dU.

Probe of unparticles at the LHC in exclusive two lepton and two photon production via photon-photon fusion

The exclusive production pp->pXp is known to be one of the most clean channels at the LHC. We investigate the potential of processes pp -> p l-l+ p and pp-> p gamma gamma p to probe scalar and tensor unparticles by considering three different forward detector acceptances; 0.0015<xi<0.15, 0.0015<xi<0.5 and 0.1<xi<0.5. We obtain 95% confidence level sensitivity limits on the unparticle couplings for various integrated luminosities.

Constraints on unparticle long range forces from big bang nucleosynthesis bounds on the variation of the gravitational coupling

We use big bang nucleosynthesis bounds on the variation of the gravitational coupling to derive constraints on the strength of the deviation from the gravitational inverse-square law due to tensor and vector unparticle exchange.

Unparticles in diphoton production to next-to-leading order in QCD at the LHC

We compute to next-to-leading order in QCD the tensor unparticle contribution to the diphoton production at the LHC, wherein the unparticle sector is a consequence of (a) scale invariance but not full conformal invariance and (b) conformal invariance. We use the semianalytical two cutoff phase-space slicing method to handle the $\mathcal{O}({\ensuremath{\alpha}}_{s})$ corrections to the $pp\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}X$ and show that our results are insensitive to the soft and collinear cutoffs. In order to avoid the contribution of the photons due to fragmentation, we employ the smooth cone isolation criterion. Significance of the QCD corrections to the diphoton events including unparticles is highlighted.

Differentiating unparticles from extra dimensions via mini black hole thermodynamics

A thermodynamics-based method is presented for differentiating mini black hole creation mechanisms in high energy parton collisions, including scenarios with large compactified extra dimensions and unparticle-enhanced gravity with real scaling dimension ${d}_{\mathcal{U}}$. Tensor unparticle interactions are shown to mimic the physics of $(2{d}_{\mathcal{U}}\ensuremath{-}2)$ noninteger extra spatial dimensions. This yields unique model-dependent production rates, Hawking temperature profiles, and decay multiplicities for black holes of mass ${M}_{\mathrm{BH}}\ensuremath{\sim}1--15\text{ }\text{ }\mathrm{TeV}$ that may be created at the LHC and other future colliders.

Unparticle effects in raret→cggdecay

In this work the flavor-changing, rare $t\ensuremath{\rightarrow}cgg$ decay induced by mediation of scalar and tensor unparticles is studied. Using the standard model result for the branching ratio of the $t\ensuremath{\rightarrow}cgg$ decay, the parameter space of ${d}_{\mathcal{U}}$ and ${\ensuremath{\Lambda}}_{\mathcal{U}}$, where the branching ratio of this decay exceeds the one predicted by the standard model, is obtained. Measurement of the branching ratio larger than ${10}^{\ensuremath{-}9}$ can give valuable information for establishing unparticle physics.

Neutrino, photon interaction in unparticle physics

We investigate the impact of unparticle physics on the annihilation of relic neutrinos with the neutrinos identified as primary source of ultra high energy (UHE) cosmic ray events, producing a cascade of photons and charged particles. We compute the contribution of the unparticle exchange to the cross-sections νν¯→γγ and νν¯→ff¯ scattering. We estimate the neutrino–photon decoupling temperature from the reaction rate of νν¯→γγ. We find that the inclusion of unparticles can in fact account for the flux of UHE cosmic rays and can also result in the lowering of neutrino–photon decoupling temperature below the QCD phase transition for unparticle physics parameters in a certain range. We calculate the mean free path of these high energy neutrinos annihilating themselves with the relic neutrinos to produce vector, axial-vector and tensor unparticles.

Comments on unparticles

We comment on several points concerning unparticles which have been overlooked in the literature. One regards Mack's unitarity constraint lower bounds on CFT operator dimensions, e.g., dV⩾3 for primary, gauge invariant, vector unparticle operators. We correct the results in the literature to account for this, and also for a needed correction in the form of the propagator for vector and tensor unparticles. We show that the unitarity constraints can be directly related to unitarity requirements on scattering amplitudes of particles, e.g., those of the Standard Model, coupled to the CFT operators. We also stress the existence of explicit Standard Model contact terms, which are generically induced by the coupling to the CFT (or any other hidden sector), and are subject to LEP bounds. Barring an unknown mechanism to tune away these contact interactions, they can swamp interference effects generated by the CFT. We illustrate these points in the context of a weakly coupled CFT example. A significant amount of the unparticle literature should be reconsidered or revised in light of the observations in this note.

Unparticle-enhanced black holes at the LHC

Based on the idea that tensor unparticles can enhance the gravitational interactions between standard model particles, potential black hole formation in high energy collisions is examined. Modifications to the horizon radius rH are derived, and the corresponding geometric cross-sections of such objects are calculated. It is shown that rH increases dramatically to the electroweak scale for masses MBH∼1–10 TeV, yielding a geometric cross-section σBH=πrH2 on the order of ⩽50 pb. This suggests that unparticle physics provides a mechanism for black hole formation in future accelerators, without the requirement of extra spatial dimensions.

Antisymmetric rank-2 tensor unparticle physics

We present the phenomenology of antisymmetric rank-2 tensor unparticle operator ${\mathcal{O}}_{\mathcal{U},\mathcal{A}}^{\ensuremath{\mu}\ensuremath{\nu}}$ with scaling dimension ${d}_{\mathcal{U}}$. We consider the physical effects of operator ${O}_{\mathcal{U},\mathcal{A}}^{\ensuremath{\mu}\ensuremath{\nu}}$ in ${Z}^{0}$ boson invisible decays ${Z}^{0}\ensuremath{\rightarrow}\mathcal{U}$, ${Z}^{0}\ensuremath{\rightarrow}b\overline{b}$ channel, the electroweak precision observable $S$ parameter, and the muon anomalous magnetic dipole moment. The ${Z}^{0}$ boson invisible decay gives a very stringent constraint in the $({\ensuremath{\Lambda}}_{\mathcal{U}},{M}_{\mathcal{U}})$ plane, and only small $r\ensuremath{\equiv}{\ensuremath{\Lambda}}_{\mathcal{U}}/{M}_{\mathcal{U}}\ensuremath{\lesssim}0.1$ is favored, when ${\ensuremath{\Lambda}}_{\mathcal{U}}$ is order of several 100 GeV. When the phenomenological parameter $\ensuremath{\mu}$, which parameterizes the scale invariance breaking, goes to 0, the $S$ parameter and the muon $(g\ensuremath{-}2)$ diverge for $1&lt;{d}_{\mathcal{U}}&lt;2$, while for nonzero $\ensuremath{\mu}$, there will be constraints on $({\ensuremath{\Lambda}}_{\mathcal{U}},{M}_{\mathcal{U}})$ which are more stringent than those obtained from collider experiments.

Unparticle physics at hadron collider via dilepton production

The scale invariant unparticle physics recently proposed by Georgi could manifest at low energies as non-integral number dU of invisible particles. Unparticles if existing, could couple to the Standard Model fields and consequently affect the collider phenomenology. We consider the DY process to explore effects of the peculiar propagator of the scalar and tensor unparticle operators. To probe these effects at hadron collider one needs to go beyond LO in QCD and hence the quantitative impact of QCD corrections for unparticle physics at LHC is investigated. We present the K-factors at LHC. Inclusion of QCD corrections to NLO stabilises the cross section with respect to scale variations.