Using linear gluon polarization inside an unpolarized proton to determine the Higgs spin and parity

Gluons inside an unpolarized proton are in general linearly polarized in the direction of their transverse momentum, rendering the LHC effectively a polarized gluon collider. This polarization can be utilized in the determination of the spin and parity of the newly found Higgs-like boson. We focus here on the determination of the spin using the azimuthal Collins-Soper angle $\phi$ distribution.Comment: 6 pages, to appear in the proceedings of the LightCone 2013+ workshop, 20-24 May 2013, Skiathos, Greec

TMD evolution and the Higgs transverse momentum distribution

The effect of the linear polarization of gluons on the transverse momentum distribution in Higgs production is studied within the framework of TMD factorization. For this purpose we consider the TMD evolution for general colorless scalar boson production, from the lower mass $C$-even scalar quarkonium states $\chi_{c0}$ and $\chi_{b0}$ to the Higgs mass scale. In the absence of an intrinsic nonperturbative linearly polarized gluon distribution the results correspond to the CSS formalism, indicating a rather rapid decrease with increasing energy scale. At the Higgs mass scale the contribution from linearly polarized gluons is in this case found to be on the percent level, somewhat larger than an earlier finding in the literature. At the lower mass scale of quarkonium states $\chi_{c0}$ and $\chi_{b0}$ we find contributions at the 15-70% level, albeit with considerable uncertainty. In the presence of an intrinsic linear gluon polarization, percent level effects are also found at the Higgs mass scale, but with a considerably slower evolution. Although these results were obtained using a model for the TMDs that are approximately Gaussian at small transverse momenta and have the correct perturbative power law fall off at large transverse momenta, it illustrates well the differences that can exist between results obtained from a TMD formalism as compared to a CSS formalism. The behavior of the TMDs at small $p_T$ can affect the results for all transverse momenta of the produced boson, even for a particle as heavy as the Higgs. The TMD evolution from $\chi_{c0}$ to $\chi_{b0}$ may be used to constrain the nonperturbative contributions and improve on the prediction of the effect at the Higgs mass scale.Comment: 12 pages, 5 figures, minor additions, matches version accepted for publication in Nuclear Physics

Linearly Polarized Gluons and the Higgs Transverse Momentum Distribution

We study how gluons carrying linear polarization inside an unpolarized hadron contribute to the transverse momentum distribution of Higgs bosons produced in hadronic collisions. They modify the distribution produced by unpolarized gluons in a characteristic way that could be used to determine whether the Higgs boson is a scalar or a pseudoscalar particle.Comment: 4 pages, 3 figures, final version, published in PR

C-type lectin signaling in response to pathogens

Kooyk, Y. van [Promotor]Geijtenbeek, T.B.H. [Copromotor]Gringhuis, S.I. [Copromotor

Double Sivers effect asymmetries and their impact on transversity measurements at RHIC

We study double transverse spin asymmetries in the Drell-Yan process at measured transverse momentum of the lepton pair. Contrary to what a collinear factorization approach would suggest, a nonzero double transverse spin asymmetry in the laboratory frame a priori does not imply nonzero transversity. TMD effects, such as the double Sivers effect, in principle form a background. Using the current knowledge of the relevant TMDs we estimate their contribution in the laboratory frame for Drell-Yan and W production at RHIC and point out a cross check asymmetry measurement to bound the TMD contributions. We also comment on the transverse momentum integrated asymmetries that only receive power suppressed background contributions.Comment: 12 pages, 11 eps figures, minor changes, matches the published versio

Accessing the Transverse Dynamics and Polarization of Gluons inside the Proton at the LHC

We argue that the study of heavy quarkonia, in particular that of $\Upsilon$, produced back-to-back with an isolated photon in $pp$ collisions at the LHC is the best --and currently unique-- way to access the distribution of both the transverse momentum and the polarization of the gluon in an unpolarized proton. These encode fundamental information on the dynamics of QCD. We have derived analytical expressions for various transverse-momentum distributions which can be measured at the LHC and which allow for a direct extraction of the aforementioned quantities. To assess the feasibility of such measurements, we have evaluated the expected yields and the relevant transverse-momentum distributions for different models of the gluon dynamics inside a proton.Comment: 5 pages, 3 figures; final version to appear in Physical Review Letter

Impact of double TMD effects on transversity measurements at RHIC

A quantitative estimate is presented for the double transverse spin asymmetries at measured q_T in both the Drell-Yan process and W-boson production due to Transverse Momentum Dependent (TMD) effects. These spin asymmetries are calculated as a function of the lepton azimuthal angle as measured in the laboratory frame. In this frame, in contrast to the Collins-Soper frame, the TMD effects contribute to the spin asymmetry A_{TT}(q_T) in the same way as transversity does, which makes them a background for transversity measurements in the Drell-Yan process and new physics studies in W-boson production. Using the current knowledge of the relevant TMDs we conclude that this background is negligible and, therefore, will not hamper transversity measurements nor new physics studies when performed in the laboratory frame. We also point out a cross-check asymmetry measurement to bound the TMD contributions, which is independent of assumptions on the sizes of the relevant TMDs