Quark States Research Articles

ObservingCP-violating Higgs signals with heavy Majorana neutrinos

We demonstrate the ability to measure the CP-phase of a Higgs boson state by looking at the decays of heavy, Majorana neutrinos in the process $pp \to H \to N N$ at the LHC. This is shown for signals with both opposite-sign ($l^{\pm} l^{\mp} W^{\pm} W^{\mp}$) and same-sign ($l^{\pm} l^{\pm} W^{\mp} W^{\mp}$) leptonic final states. These signals are investigated in the general framework of a sequential fourth generation of fermions with an additional right-handed neutrino. Such a scenario would naturally give rise to heavy Majorana neutrinos as well as significant enhancements to Higgs production via gluon fusion due to the contributions of the new, heavy quark states running in the fermion loops. Combined with the low background inherent to a same-sign lepton signal, this could be a useful way to investigate the CP-nature of a Higgs boson state at the LHC.

One-loop operator matching in the static heavy and domain-wall light quark system with O(a) improvement

We discuss perturbative O(g^2a) matching with static heavy quarks and domain-wall light quarks for lattice operators relevant to B-meson decays and $B^0$-$\bar{B}^0$ mixing. The chiral symmetry of the light domain-wall quarks does not prohibit operator mixing at O(a) for these operators. The O(a) corrections to physical quantities are non-negligible and must be included to obtain high-precision simulation results for CKM physics. We provide results using plaquette, Symanzik, Iwasaki and DBW2 gluon actions and applying APE, HYP1 and HYP2 link-smearing for the static quark action.

Proper identification of the gluon spin

Properties of the recently proposed gauge-invariant gluon spin Sg are studied and compared to the usually defined “gluon polarization” Δg. By explicit 1-loop calculations in a quark state, it is found that Sg=59Δg. Furthermore, 45 of Sg can actually be identified as a “static-field” contribution and shown to cancel exactly an analogous static term in the gluon orbital angular momentum Lg, leaving Sg+Lg unaltered. These observations suggest that by an alternative definition, the gluon contribution to the nucleon spin may be drastically smaller than in the conventional wisdom.

Determination of the static potential with dynamical fermions

We present in detail a technique to extract the potential between a static quark and anti-quark pair from Wilson loops measured on dynamical configurations. This technique is based on HYP smearing and leads to an exponential improvement of the noise-to-signal ratio of Wilson loops. We explain why the correct continuum potential is obtained and show numerical evidence that the cut-off effects are small. We present precise results for the non-perturbative potential. As applications, we determine the scale r 0 / a and study the shape of the static potential in the range of distances around r 0 , where it can be compared with phenomenological potential models.

A NONPERTURBATIVE MODEL FOR THE STRONG RUNNING COUPLING WITHIN POTENTIAL APPROACH

A nonperturbative model for the QCD invariant charge, which contains no low-energy unphysical singularities and possesses an elevated higher-loop corrections stability, is developed in the framework of potential approach. The static quark–antiquark potential is constructed by making use of the proposed model for the strong running coupling. The obtained result coincides with the perturbative potential at small distances and agrees with relevant lattice simulation data in the nonperturbative physically-relevant region. The developed model yields a reasonable value of the QCD scale parameter, which is consistent with its previous estimations obtained within potential approach.

Probing boundary-corrections to Nambu-Goto open string energy levels in 3d SU(2) gauge theory

We measure the energy levels of the excitations of the flux tube between static quark and antiquark in three-dimensional SU(2) gauge theory. Combining exponential error reduction techniques and a variational method we are able to reduce the errors for the excited states significantly and to extract excited states in distinct parity and charge conjugation channels. It is conjectured that the infrared behavior (at large q\bar{q} separation R) of the flux tube is governed by an effective string theory. Indeed previous simulations show good agreement between lattice data and predictions from Nambu-Goto string theory. Recently, new results on the effective string theory obtained corrections to the Nambu-Goto predictions and showed that for the open string in three dimensions first corrections should appears at order 1/R^4. They correspond to boundary terms in the worldsheet field theory. These corrections are presumably small for the ground state, but significantly larger for the excited states and lift the degeneracies of the free theory. Assuming this functional form of the correction, we obtain for the coefficient b_2=-0.5(2)(2).

ϒ production as a probe for early state dynamics in high energy nuclear collisions at RHIC

ϒ production in heavy ion collisions at RHIC energy is investigated. While the transverse momentum spectra of the ground state ϒ(1s) are controlled by the initial state Cronin effect, the excited bb¯ states are characterized by the competition between the cold and hot nuclear matter effects and sensitive to the dissociation temperatures determined by the heavy quark potential. We emphasize that it is necessary to measure the excited heavy quark states in order to extract the early stage information in high energy nuclear collisions at RHIC.

Near-maximal mixing of scalar gluonium and quark mesons: A Gaussian sum-rule analysis

Gaussian QCD sum-rules are ideally suited to the study of mixed states of gluonium (glueballs) and quark ( q q ¯ ) mesons because of their capability to resolve widely-separated states of comparable strength. The analysis of the Gaussian QCD sum-rules (GSRs) for all possible two-point correlation functions of gluonic and non-strange ( I = 0 ) quark scalar ( J P C = 0 + + ) currents is discussed. For the non-diagonal sum-rule of gluonic and q q ¯ currents we show that perturbative and gluon condensate contributions are chirally suppressed compared to non-perturbative effects of the quark condensate, mixed condensate, and instantons, implying that the mixing of quark mesons and gluonium is of non-perturbative origin. The independent predictions of the masses and relative coupling strengths from the non-diagonal and the two diagonal GSRs are remarkably consistent with a scenario of two states with masses of approximately 1 GeV and 1.4 GeV that couple to significant mixtures of quark and gluonic currents. The mixing is nearly maximal with the heavier mixed state having a slightly larger coupling to gluonic currents than the lighter state.

Describing the strongly interacting quark-gluon plasma through the Friedberg-Lee model

The non-topological FL model is studied at finite temperature and density. The soliton solutions of the FL model in deconfinement phase transition are solved and thoroughly discussed for different boundary conditions. We indicate that the solitons before and after the deconfinement have different physical meanings: the soliton before deconfinement represents hadron, while the soliton after the deconfinement represents the bound state of quarks which leads to a sQGP phase. The corresponding phase diagram is given.

Nonextensive statistical effects in the hadron to quark–gluon phase transition

We investigate the relativistic equation of state of hadronic matter and quark–gluon plasma at finite temperature and baryon density in the framework of nonextensive statistical mechanics, characterized by power-law quantum distributions. We study the phase transition from hadronic matter to quark–gluon plasma by requiring the Gibbs conditions on the global conservation of baryon number and electric charge fraction. We show that nonextensive statistical effects play a crucial role in the equation of state and in the formation of mixed phase also for small deviations from the standard Boltzmann–Gibbs statistics.

On relation between the quark–gluon bag surface tension and the colour tube string tension

We revisit the bag phenomenology of deconfining phase transition aiming to replenish it by introducing systematically the bag surface tension. Comparing the free energies of such bags and the strings confining the static quark–antiquark pair, we express the string tension in terms of the bag surface tension and the bulk pressure in order to estimate the bag characteristics using the lattice QCD (LQCD) data. Our analysis of the bag entropy density demonstrates that the surface tension coefficient is amazingly negative at the cross-over (continuous transition). The approach developed allows us to naturally account for an origin of a pronounced maximum (observed in the LQCD studies) in the behaviour of heavy quark–antiquark pair entropy. The vicinity of the (tri-)critical endpoint is also analyzed to clarify the meaning of vanishing surface tension coefficient.

Convergence of the self-energy in a relativistic chiral quark model: excited nucleon and Δ sector

A convergence of the valence quark self-energies in the 1S, 2S, 1P1/2, 1P3/2 orbits induced by pion- and gluon-field configurations is shown in the frame of a relativistic chiral quark model. It is shown that in order to reach a convergence, one needs to include the contribution of the intermediate quark and anti-quark states with the total momentum up to j = 25/2. It is argued that a restriction to the lowest mode when estimating the self-energy is not a good approximation.

Implication on the pion distribution amplitude from the pion-photon transition form factor with the newBABARdata

The new BABAR data on the pion-photon transition form factor arouses people's interest for the determination of the pion distribution amplitude. To explain the data, we take both the leading valence quark state's and the nonvalence quark state's contributions into consideration, where the valence quark part up to next-to-leading order is presented and the nonvalence quark part is estimated by a phenomenological model based on its limiting behavior at both ${Q}^{2}\ensuremath{\rightarrow}0$ and ${Q}^{2}\ensuremath{\rightarrow}\ensuremath{\infty}$. Our results show that to be consistent with the new BABAR data at the large ${Q}^{2}$ region, a broader amplitude other than the asymptoticlike pion distribution amplitude should be adopted. The broadness of the pion distribution amplitude is controlled by a parameter $B$. It has been found that the new BABAR data at low and high energy regions can be explained simultaneously by setting $B$ to be around 0.60, in which the pion distribution amplitude is closed to the Chernyak-Zhitnitsky form.

Dynamical study of the possible molecular state X(3872) with the s-channel one gluon exchange interaction

The recently observed X(3872) resonance, which is difficult to assign a conventional cc̄ charmonium state in the quark model, may be interpreted as a molecular state. Such a molecular state is a hidden flavor four quark state because of its charmonium-like quantum numbers. The s-channel one gluon exchange is an interaction which only acts in the hidden flavor multi-quark system. In this paper, we will study the X(3872) and other similiar hidden flavor molecular states in a quark model by taking into account the s-channel one gluon exchange interaction.

Holographic penta and hepta quark state in confining gauge theories

We study a new embedding solutions of D5 brane in an asymptotic AdS${}_5\times S^5$ space-time, which is dual to a confining $SU(N_c)$ gauge theory. The D5 brane is wrapped on $S^5$ as in the case of the vertex of holographic baryon. However, the solution given here is different from the usual baryon vertex in the point that it couples to $k$-anti-quarks and $N_c+k$ quarks on the opposite two points of $S^5$, the north and south poles, respectively. The total quark number of this state is preserved as $N_c$ when minus one is assigned to anti-quark, then it forms a color singlet like the baryon. However, this includes anti-quarks and quarks, whose number is larger than that of the baryon. When we set as $N_c=3$, we find the so called penta and hepta-quark states. We study the dynamical properties of these states by solving the vertex and string configurations for such states. The mass spectra of these states and the tension of the stretched vertex are estimated, and they are compared with that of the baryon.

The stability of mesons near event horizon of black hole

SUMMARY AND CONCLUSION In this paper first we compared entropies of final states in Dirac fields as well as in scalar fields. Next we concluded that near black hole mesons are stable. After that we compared the total cross section for mesons produced from one black hole. We saw that the more the mass of the quark within the hadrons, the lower is the cross section. Finally we calculated the resulting informa-tion transformation from the collapsing matter to the state of outgoing Hawking radiation for mesons. We observe that due to the deviation of the f from unity, some of information is lost in black holes. REFERENCES Ahn D (2006). Final state boundary condition of the Schwarzschild black hole. Phys. Rev. D. 74, 084010. Ahn D (2007). Control of black hole evaporation? JHEP. 0703: 021. Zomorrodian et al. 1053 n n u -Schuller I (2008). Black hole final state for the Dirac fields In Schwarzschild spacetime. JHEP. 0806: 062. Argyres PC, Dimopoulos S, March-Russell J (1998). Black Holes and Sub-millimeter Dimensions. Phys. Lett., B441: 96. Chamblin A, Cooper F, Nayak GC (2009).Top Quark Production from Black Holes at the CERN LHC. Phys. Lett., B672: 147-151. Cooper F, Mottola E, Nayak GC (2003). Minijet Initial Conditions For Non-Equilibrium Parton Evolution at RHIC and LHC. Phys. Lett. B, 555: 181. Cooper F, Nayak GC (2004). Interaction of a TeV scale black hole with the quark-gluon plasma at CERN LHC. Phys. Rev. D. 69, 065010. Deutsch D (1991). Quantum mechanics near closed timelike lines. Phys. Rev. D., 44: 3197. Dimopoulos GC, Landsberg G (2001). Black Holes at the Large Hadron Collider. Phys. Rev. Lett., 87: 161602. Ge HX, Shen GY (2005). Reconsidering the black hole final state in Dirac fields. Phys.Lett., B612: 61-64. Giddings SB, Thomas S (2002). High energy colliders as black hole factories: end of short distance physics. Phys. Rev. D., 65: 056010. Gottesman D, Preskill J (2004). Comment on The black hole final JHEP., 0403: 026. Hawking SW (1973). Particle creation by black holes. Common.Math. Phys., 43: 199. Hawking SW (1974). Black-hole evaporation. Nature, 248: 30. Hawking SW (1976). Breakdown of predictability in gravitational collapse. Phys. Rev. D., 14: 2466. Horowitz GT, Maldacena J (2004). black hole final state. J. High. Energy. Phys., 02: 008. Millers DE (2004). Entropy for $SU(3)_c$ Quark States. Eur. Phys. J., C34: 435-437. Schumacher B, Bennett CH (2007). unpublished. See http://qpip-server.tcs.tifr.res.in qpip/HTML/Courses/Bennett/TIFR5.pdf,slides 39-47. Unruh WG (1976). Notes on Black Hole Evaporation. Phys. Rev. D, 14: 870.

Confinement singularities in two-pion decays of mesons

We consider as an example the two-pion decay of the ρ meson, the 3S1q\( \bar q \) state of the constituent quarks—the decay being determined by the transition q\( \bar q \) → ππ contains information about confinement interactions. One can specify in this decay two types of transitions: (i) the bremsstrahlung radiation of a pion q → q + π (or \( \bar q \) → \( \bar q \) + π) with a subsequent fusion q\( \bar q \) → π, and (ii) the direct transition q\( \bar q \) → ππ. We demonstrate how in the amplitudes of the corresponding transitions the quark singularities have to disappear, i.e., what is the way the quark confinement at relatively short distances can be realized. We calculate and estimate the contributions of processes with bremsstrahlung radiation of the pion and of the direct transition q\( \bar q \) → ππ. The estimates demonstrate that the processes involving the direct transition q\( \bar q \) → ππ are necessary, but they cannot be determined unambiguously by the decay ρ(775) → ππ. We conclude that for the determination of the q\( \bar q \) → ππ transition more complete data on the resonance decays into the ππ channels are needed than those available at the moment.

Massive quark scattering at strong coupling from AdS/CFT

We extend the analysis of Alday and Maldacena for obtaining gluon scattering amplitudes at strong coupling to include external massive quark states. Our quarks are actually the $\mathcal{N}=2$ hypermultiplets which arise when $D7$-brane probes are included in the ${\mathrm{AdS}}_{5}\ifmmode\times\else\texttimes\fi{}{S}^{5}$ geometry. We work in the quenched approximation, treating the $\mathcal{N}=2$ matter multiplets as external sources coupled to the $\mathcal{N}=4$ supersymmetric Yang-Mills fields. We first derive appropriate massive-particle boundary conditions for the string scattering world sheets. We then find an exact world sheet which corresponds to the scattering of two massive quarks and two massless gluons and extract from this the associated scattering amplitude. We also find the world sheet and amplitude for the scattering of four massive quarks. Our world sheet solutions reduce to the four massless gluon solution of Alday and Maldacena in the limit of zero quark mass. The amplitudes we compute can also be interpreted in terms of 2-2 scattering involving gluons and massive $W$ bosons.

Width of the Confining String in Yang-Mills Theory

We investigate the transverse fluctuations of the confining string connecting two static quarks in (2+1)D SU(2) Yang-Mills theory using Monte Carlo calculations. The exponentially suppressed signal is extracted from the large noise by a very efficient multilevel algorithm. The resulting width of the string increases logarithmically with the distance between the static quark charges. Corrections at intermediate distances due to universal higher-order terms in the effective string action are calculated analytically. They accurately fit the numerical data.

Fourier analysis of the flux-tube distribution in SU(3) lattice QCD

This Letter presents a novel analysis of the action/energy density distribution around a static quark–antiquark pair in SU(3) lattice quantum chromodynamics. Using the Fourier transformation of the link variable, we remove the high-momentum gluon and extract the flux-tube component from the action/energy density. When the high-momentum gluon is removed, the statistical fluctuation is drastically suppressed, and the singularities from the quark self-energy disappear. The obtained flux-tube component is broadly distributed around the line connecting the quark and the antiquark.