Tests of BSM Higgs interactions by the combination $(κ_V^2-κ_{2V})$ in HHjj production at LHC

TL;DR

The paper investigates Beyond Standard Model Higgs interactions in HEFT, focusing on the independent parameters a and b that map to κ_V and κ_{2V}, and, crucially, on the combination a^2−b (i.e., κ_V^2−κ_{2V}). It demonstrates that HHjj production in Vector Boson Fusion is highly sensitive to this combination, with high-energy VV→HH amplitudes and differential observables (notably the Higgs rapidity η_H) reflecting central, highly transversely produced Higgs pairs when a^2−b≠0. The study provides parton-level and detector-level analyses (including showering and CMS Phase-2 detector effects) for the final state HH→bbγγ with two light jets, presenting optimized selection strategies (based on η_γγ and P_T,γγ) to enhance HL-LHC sensitivity. By combining cross-section and differential information and performing detector-level simulations, the work shows that HL-LHC can place meaningful constraints on the combination κ_V^2−κ_{2V}, potentially revealing correlations between HVV and HHVV interactions arising from underlying UV physics, or otherwise tightening limits on BSM Higgs scenarios within HEFT.

Abstract

In this work, we study the potential of analyzing the particular combination of $κ$ modifiers given by $κ_V^2-κ_{2V}$ to disentangle Beyond Standard Model Higgs signals in double Higgs production with two extra light jets at LHC. We use the Higgs Effective Field Theory approach, HEFT, for the gauge invariant description of these two $κ_V$ and $κ_{2V}$ parameters representing the BSM interactions of the Higgs particle with the electroweak gauge bosons, $HVV$ and $HHVV$ respectively. We illustrate the bonus of studying this particular combination $κ_V^2-κ_{2V}$ focusing in just one process, $HHjj$, instead of studying $κ_V$ and $κ_{2V}$ separately using various processes. For the detailed analysis here, we focus on the particular final state $H(\to γγ) H (\to b \bar b)jj'$, with two photons, two b-jets and two light jets, which we analyze fully including parton showering, fragmentation, hadronization and detector effects, in both signal and main background. We find that the sensitivity to $κ_V^2-κ_{2V}$ could be notably improved at the HL-LHC by the proper cuts on the final state $b \bar b γγjj'$ that select optimally the events with VBF-topology and $HH$-topology. In particular, we propose strategies based on a good isolation of $γγ$ and b-jet pairs, and focus specially on specific variables like $η_{γγ}$ and $P^T_{γγ}$ where the signal events distributions may efficiently discriminate between BSM signal versus SM background. We will show here how the high transversality of these two pairs in the signal (inherited from the high transversality of the $H$'s) is correlated with the non-vanishing value of this $(κ_V^2-κ_{2V})$ combination.

Figures (17)

• Figure 3.1: Feynman diagrams contributing to $VV \to HH$ (with $VV=WW, ZZ$) within the LO-HEFT in the Unitary gauge. From left to right, diagrams for the s-channel, contact c-channel, t-channel and u-channel. Effective vertices proportional to $\kappa_V=a$ and $\kappa_{2V}=b$ are colored in red and blue, respectively.
• Figure 3.2: Predictions within the HEFT for the differential cross section of $WW \to HH$ with respect to the final Higgs pseudo-rapidity, $\eta_H$. The colored lines are for different choices of the combination $(a^2-b)$ defining some examples of BSM scenarios. We take $(a^2-b)=$ 0 (red line), 0.05 (purple line), 0.2 (blue line) and 0.8 (green line). Here the total center-of-mass energy is fixed to $\sqrt{s}=3$ TeV. The plot on the left is for $a=0.7$, and the plot on the right is for $b=2$.
• Figure 4.1: Schematic of the two different topology classes involved in the EW Higgs boson pair production in $pp$ collisions, the associated production (double Higgs-strahlung) [left] and the vector boson fusion (VBF) [right]. Here, $V$ refers generically to either $W^\pm$ or $Z$ and $q$ denotes either quarks $q$ or anti-quarks $\overline{q}$.
• Figure 4.2: Parton-level SM differential cross section of the double Higgs production with respect to the light quark pair's invariant mass [left], and to the light quarks pseudo-rapidity difference [right], for different kinematic cuts applied to the event's phase space. In green, the initial signal. In blue, reduced to events with $\eta_{j_1} \times \eta_{j_2} < 0$, with an acceptance of 83.52 $\%$. In red, reduced to events with $\eta_{j_1} \times \eta_{j_2} < 0$, as well as $\left| \eta_{j} \right| > 2$, with an acceptance of 47.90 $\%$.
• Figure 4.3: Parton-level SM differential cross section of the double Higgs production with respect to the Higgs boson pair's invariant mass [left], and to the leading Higgs pseudo-rapidity [right], for different kinematic cuts applied to the event's phase space. In green, the initial signal. In blue, reduced to events with $\eta_{j_1} \times \eta_{j_2} < 0$, with an acceptance of 83.52 %. In red, reduced to events with $\eta_{j_1} \times \eta_{j_2} < 0$, as well as $\left| \eta_{j} \right| > 2$, with an acceptance of 47.90 %.