Search

We present results for the volume dependence of baryon number fluctuations in the vicinity of the (conjectured) critical endpoint of QCD. They are extracted from the nonperturbative quark propagator that is obtained as a solution to a set of truncated Dyson–Schwinger equations of (2 + 1)-flavor QCD in Landau gauge, which takes the backcoupling of quarks onto the Yang–Mills sector explicitly into account. This well-studied system predicts a critical endpoint at moderate temperatures and rather large chemical potential. We investigate this system at small and intermediate finite, three-dimensional, cubic volumes and study the resulting impact on baryon number fluctuations and ratios thereof up to fourth order in the region of the critical endpoint. Due to the limitations of our truncation, the results are quantitatively meaningful only outside the critical scaling region of the endpoint. We find that the fluctuations are visibly affected by the finite volume, particularly for antiperiodic boundary conditions, whereas their ratios are practically invariant. [ABSTRACT FROM AUTHOR]

Recently there is a resurrection in the study of heavy quark bound states in a hot and baryonless matter with an ambient magnetic field but the matter produced at heavy-ion collider experiments is not perfectly baryonless, so we wish to explore the effect of small baryon asymmetry on the in-medium properties of the heavy quark bound states submerged in a strongly magnetized hot quark matter. Therefore, we have first given a revisit to the general covariant tensor structure of gluon self-energy in the above environment to compute the resummed propagator for gluons. This resummed propagator embodies the properties of medium, which gets translated into the (complex) potential between Q and Q ¯ placed in the medium. We observe that the baryon asymmetry makes the real-part of potential slightly more attractive and weakens the imaginary-part. This opposing effects thus lead to the enhancement of binding energies and the reduction of thermal widths of Q Q ¯ ground states, respectively. Finally, the properties of quarkonia thus deciphered facilitate to compute the dissociation points of J / ψ and ϒ, which are found to have slightly larger values in the presence of baryon asymmetry. For example, J / ψ gets dissociated at 1.64 T c , 1.69 T c , and 1.75 T c , whereas ϒ is dissociated at 1.95 T c , 1.97 T c and 2.00 T c , for μ = 0 , 60 and 100 MeV, respectively. This observation prevents early dissociation of quarkonia in the matter produced at ultrarelativistic heavy ion collisions with a small net baryon number, compared to the ideal baryonless matter. [ABSTRACT FROM AUTHOR]

In the E 6 inspired composite Higgs model (E 6 CHM) the strongly interacting sector possesses an S U ( 6 ) global symmetry which is expected to be broken down to its S U ( 5 ) subgroup at the scale f ≳ 10 TeV . This breakdown results in a set of pseudo-Nambu–Goldstone bosons (pNGBs) that includes one Standard Model (SM) singlet scalar, a SM-like Higgs doublet and an S U ( 3 ) C triplet of scalar fields, T . In the E 6 CHM the Z 2 L symmetry, which is a discrete subgroup of the U ( 1 ) L associated with lepton number conservation, can be used to forbid operators which lead to rapid proton decay. The remaining baryon number violating operators are sufficiently strongly suppressed because of the large value of the scale f . We argue that in this variant of the E 6 CHM a sizeable baryon number asymmetry can be induced if CP is violated. At the same time, the presence of the S U ( 3 ) C scalar triplet with mass in the few TeV range may give rise to spectacular new physics signals that may be detected at the LHC in the near future. [ABSTRACT FROM AUTHOR]

J-PARC is a Japanese proton synchrotron accelerator facility, and is under consideration of an upgrade for accelerating heavy ions. A beam rate of about 10 11 Hz is expected with the upgraded accelerator scheme, with which the QCD phase structure, hadrons under a high baryon density, and multi-strange hypernuclei can be studied. In this paper, we discuss the plan for the upgrade and the conceptual design of the detectors for several physics cases. [ABSTRACT FROM AUTHOR]

We present results for the QCD Equation of State at non-zero chemical potentials corresponding to the conserved charges in QCD using Taylor expansion upto sixth order in the baryon number, electric charge and strangeness chemical potentials. The latter two are constrained by the strangeness neutrality and a fixed electric charge to baryon number ratio. In our calculations, we use the Highly Improved Staggered Quarks (HISQ) discretization scheme at physical quark masses and at different values of the lattice spacings to control lattice cut-off effects. Furthermore we calculate the pressure along lines of constant energy density, which serve as proxies for the freeze-out conditions and discuss their dependence on μ B , which is necessary for hydrodynamic modelling near freezeout. We also provide an estimate of the radius of convergence of the Taylor series from the 6th order coefficients which provides a new constraint on the location of the critical end-point in the T - μ B plane of the QCD phase diagram. [ABSTRACT FROM AUTHOR]

Up to 6 th order cumulants of fluctuations of net baryon-number, net electric charge and net strangeness as well as correlations among these conserved charge fluctuations are now being calculated in lattice QCD. These cumulants provide a wealth of information on the properties of strong-interaction matter in the transition region from the low temperature hadronic phase to the quark-gluon plasma phase. They can be used to quantify deviations from hadron resonance gas (HRG) model calculations which frequently are used to determine thermal conditions realized in heavy ion collision experiments. Already some second order cumulants like the correlations between net baryon-number and net strangeness or net electric charge differ significantly at temperatures above 155 MeV in QCD and HRG model calculations. We show that these differences increase at non-zero baryon chemical potential constraining the applicability range of HRG model calculations to even smaller values of the temperature. [ABSTRACT FROM AUTHOR]

We present recent results from lattice QCD relevant for the study of strongly interacting matter as it is produced in heavy ion collision experiments. The equation of state at non-vanishing density from a Taylor expansion up to 6 th order will be discussed for a strangeness neutral system and using the expansion coefficients of the series limits on the critical point are estimated. Chemical freeze-out temperatures from the STAR and ALICE Collaborations will be compared to lines of constant physics calculated from the Taylor expansion of QCD bulk thermodynamic quantities. We show that qualitative features of the s NN dependence of skewness and kurtosis ratios of net proton-number fluctuations measured by the STAR Collaboration can be understood from QCD results for cumulants of conserved baryon-number fluctuations. As an example for recent progress towards the determination of spectral and transport properties of the QGP from lattice QCD, we will present constraints on the thermal photon rate determined from a spectral reconstruction of continuum extrapolated lattice correlation functions in combination with input from most recent perturbative calculations. [ABSTRACT FROM AUTHOR]

At RHIC, enhancements in the baryon-to-meson ratio for light hadrons and hadrons containing strange quarks have been observed in central heavy-ion collisions compared to those in p+p and peripheral heavy-ion collisions in the intermediate transverse momentum ( p T ) range ( 2 < p T < 6 GeV / c ). This can be explained by the hadronization mechanism involving multi-parton coalescence. Λ c is the lightest charmed baryon with mass close to that of the D 0 meson, and has shorter life time than D 0 ( c τ ∼ 60 μ m ). Different models predict different magnitudes of enhancement in the Λ c / D 0 ratio depending on the degree to which charm quarks are thermalized in the medium and how the coalescence mechanism is implemented. In these proceedings, we report the first measurement of Λ c production in heavy-ion collisions using the Heavy Flavor Tracker at STAR. The invariant yield of Λ c for 3 < p T < 6 GeV / c is measured in 10–60% central Au+Au collisions at s NN = 200 GeV . The Λ c / D 0 ratio is compared to different model calculations, and the physics implications are discussed. [ABSTRACT FROM AUTHOR]

The baryon electromagnetic form factors are expressed in terms of two-dimensional densities describing the distribution of charge and magnetization in transverse space at fixed light-front time. We calculate the transverse densities of the spin-1/2 flavor-octet baryons at peripheral distances b = O ( M π − 1 ) using methods of relativistic chiral effective field theory ( χ EFT) and dispersion analysis. The densities are represented as dispersive integrals over the imaginary parts of the form factors in the timelike region (spectral functions). The isovector spectral functions on the two-pion cut t > 4 M π 2 are calculated using relativistic χ EFT including octet and decuplet baryons. The χ EFT calculations are extended into the ρ meson mass region using an N / D method that incorporates the pion electromagnetic form factor data. The isoscalar spectral functions are modeled by vector meson poles. We compute the peripheral charge and magnetization densities in the octet baryon states, estimate the uncertainties, and determine the quark flavor decomposition. The approach can be extended to baryon form factors of other operators and the moments of generalized parton distributions. [ABSTRACT FROM AUTHOR]

We build a supersymmetric version with gauge symmetry, where is a new charge and and are the usual baryonic and leptonic numbers. The model has three right-handed neutrinos with identical charges, and can accommodate all fermion masses at the tree level. In particular, the type I seesaw mechanism is implemented for the generation of the active neutrino masses. We obtain the mass spectra of all sectors and for the scalar one we also give the flat directions allowed by the model. [ABSTRACT FROM AUTHOR]

We study the phenomenology of a supersymmetric extension of the Standard Model with an R-symmetry under which R-charges correspond to the baryon number. This identification allows for the presence in the superpotential of the R-parity violating term λ U D D without breaking baryon number, which loosens several bounds on this operator while changing considerably the phenomenology. However, the R-symmetry cannot remain exact as it is at least broken by anomaly mediation. Under these conditions, we investigate the constraints coming from baryon number violating processes and flavour physics and find that, in general, they are lessened. Additionally, we examine recent ATLAS and CMS experimental searches and use these to place limits on the parameter space of the model. This is done for both stop production, which now features both pair and resonant production, and pair production of the first two generations of squarks. Finally, we study the implications this model has on baryogenesis. We find that successful baryogenesis can potentially be achieved, but only at the cost of breaking the R-symmetry by a significant amount. [ABSTRACT FROM AUTHOR]

We present DsixTools, a Mathematica package for the handling of the dimension-six standard model effective field theory. Among other features, DsixTools allows the user to perform the full one-loop renormalization group evolution of the Wilson coefficients in the Warsaw basis. This is achieved thanks to the SMEFTrunner module, which implements the full one-loop anomalous dimension matrix previously derived in the literature. In addition, DsixTools also contains modules devoted to the matching to the $$\Delta B = \Delta S = 1,2$$ and $$\Delta B = \Delta C = 1$$ operators of the Weak Effective Theory at the electroweak scale, and their QCD and QED Renormalization group evolution below the electroweak scale. [ABSTRACT FROM AUTHOR]

We investigate the possibility to find an ultraviolet completion of the simple extensions of the Standard Model where baryon number is a local symmetry. In the context of such theories one can understand the spontaneous breaking of baryon number at the low scale and the proton stability. We find a simple theory based on S U ( 4 ) C ⊗ S U ( 3 ) L ⊗ S U ( 3 ) R where baryon number is embedded in a non-Abelian gauge symmetry. We discuss the main features of the theory and the possible implications for experiments. This theory predicts stable colored and/or fractional electric charged fields which can give rise to very exotic signatures at the Large Hadron Collider experiments such as CMS and ATLAS. We further discuss the embedding in a gauge theory based on S U ( 4 ) C ⊗ S U ( 4 ) L ⊗ S U ( 4 ) R which could define the way to achieve the unification of the gauge interactions at the low scale. [ABSTRACT FROM AUTHOR]

Baryon and lepton numbers being accidental global symmetries of the Standard Model (SM), it is natural to promote them to local symmetries. However, to preserve anomaly-freedom, only combinations of B-L are viable. In this spirit, we investigate possible dark matter realizations in the context of the $$U(1)_\mathrm{B{-}L}$$ model: (i) Dirac fermion with unbroken B-L; (ii) Dirac fermion with broken B-L; (iii) scalar dark matter; (iv) two-component dark matter. We compute the relic abundance, direct and indirect detection observables and confront them with recent results from Planck, LUX-2016, and Fermi-LAT and prospects from XENON1T. In addition to the well-known LEP bound $$M_{Z^{\prime }}/g_\mathrm{BL} \gtrsim 7$$ TeV, we include often ignored LHC bounds using 13 TeV dilepton (dimuon + dielectron) data at next-to-leading order plus next-to-leading logarithmic accuracy. We show that, for gauge couplings smaller than 0.4, the LHC gives rise to the strongest collider limit. In particular, we find $$M_{Z^{\prime }}/g_\mathrm{BL} > 8.7$$ TeV for $$g_\mathrm{BL}=0.3$$ . We conclude that the NLO+NLL corrections improve the dilepton bounds on the $$Z^{\prime }$$ mass and that both dark matter candidates are only viable in the $$Z^{\prime }$$ resonance region, with the parameter space for scalar dark matter being fully probed by XENON1T. Lastly, we show that one can successfully have a minimal two-component dark matter model. [ABSTRACT FROM AUTHOR]