We observe that most studies of axion-like particle (ALP) production channels at the Large Hadron Collider (LHC) focus on a single type of ALP operator for each process in the effective field theory framework. In this work, we propose an alternative approach that considers two or more types of relevant ALP effective operators together in some specific ALP production channels and study their interference effects. Using the pp → tja process with a → γγ as an example, we show that this approach allows us to constrain the ALP interactions with both the W boson and the top quark, as well as their interference in a single process. For the final state with two isolated photons and a top quark decaying semi-leptonically, we predict that the future bounds on the ALP decay constant can reach around f  a  ~ 10 (20) TeV for 25 GeV &lt; M  a  &lt; 100 GeV at the LHC with 300 (3000) fb−1 luminosity.

Taiwan

South Korea

Kingman Cheung

China

Chih-Ting Lu

C.J. Ouseph

Priyanka Sarmah

Exploring interference effects between two ALP effective operators at the LHC

The production of a Higgs boson in association with a Z at an electron-positron collider is one of the cleanest methods for the measurement of the couplings of the Higgs boson. In view of the large production cross section at energies a little above the threshold, it seems feasible to make a more detailed study of the process by measuring the cross sections for polarized Z in order to measure possible anomalous ZZH couplings. We show that certain combinations of cross sections in <math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>→</mo><mi>Z</mi><mi>H</mi></math> with different Z polarizations help to enhance or isolate the effect of one of the two kinds of anomalous ZZH couplings possible on general grounds of CP and Lorentz invariance. These combinations can be useful to get information on the ZZH coupling in the specific contexts of an effective field theory, two-Higgs-doublet models, and composite Higgs models, in a relatively model-independent fashion. We find in particular that the longitudinal helicity fraction of the Z is expected to be insensitive to anomalous couplings, and would be close to its value in the standard model in the scenarios we consider. We also discuss the sensitivity of the proposed measurements to the anomalous couplings, including longitudinal beam polarizations, which suppress backgrounds, and can improve the sensitivity if appropriately chosen.

India

Kumar Rao

Saurabh D. Rindani

Balbeer Singh

Polarized cross sections in Higgsstrahlung for the determination of anomalous Couplings

It is shown that a certain angular asymmetry of charged leptons produced in the decay of Z in the process <math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>→</mo><mi>Z</mi><mi>H</mi></math>, related to a tensor polarization component of the Z, can be used to constrain the anomalous triple-Higgs coupling, independent of the other anomalous couplings like the ZZH coupling which dominate at tree level. This is because the angular asymmetry is odd under naïve time reversal, and hence dependent on loop-level contributions. At a future <math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></math> collider like the International Linear Collider (ILC), for example, a limit of about 3.4 might be placed on the ratio of the actual triple Higgs coupling to that predicted in the standard model for a centre-of-mass energy of 500 GeV and an integrated luminosity of 30 fb$^{−1}$ with electron and positron beams having longitudinal polarization of <math><mo>−</mo><mn>80</mn><mtext>%</mtext></math> and <math><mo>+</mo><mn>30</mn><mtext>%</mtext></math>, respectively.

Use of Polarization in → to measure the triple-Higgs coupling

We estimate model independent bounds that could be obtained on the anomalous ZZH vertex using polarization parameters of the Z boson produced in the Higgstrahlung process at the LHC. We calculate the eight independent polarization parameters from the spin density matrix elements of the Z, which can probe underlying new physics contributions to ZH production. By using the approach that connects these polarization observables to the coefficients in the angular distribution of the decay products of the Z, we estimate the limits on the anomalous ZZH coupling that can be obtained at the 14 TeV LHC.

Study of anomalous gauge-Higgs couplings using boson polarization at LHC

We study possible new physics interactions in the ZZH vertex contributing to the Higgsstrahlung process <math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>→</mo><mi>Z</mi><mi>H</mi></math> at proposed future <math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></math> colliders using the polarization of the Z as a probe. We calculate the spin density matrix of the Z for the process and determine the eight independent polarization parameters of the Z boson which have the potential to constrain the anomalous couplings. We study angular asymmetries using the decay leptons from the Z boson which are simply related to the polarization observables. We also estimate the limits that can be placed on the anomalous couplings using measurements of these angular asymmetries at centre of mass energies of 250 GeV and 500 GeV and various combinations of polarized <math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup></math> and <math><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></math> beams.