Robert Harlander

Institut für Theoretische Physik und Kosmologie
Fakultät für Mathematik, Informatik, Naturwissenschaften
RWTH Aachen University
52056 Aachen, Germany
fax: +49-241-80-22187
phone: +49-241-80-27045


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Higgs WG

LHC and Philosophy

Robert Harlander: Research Interests -/- Home -/- TTP Karlsruhe -/- CERN Theory -/- HET Brookhaven

Research interests:

Higher order SUSY Higgs production at LHC Electro-weak observables Asymptotic Expansions Top pairs near threshold

Higgs production at hadron colliders

  1. Gluon fusion
    1. QCD corrections
    2. Pseudoscalar Higgs
    3. Supersymmetry
    4. Beyond the Heavy Top Limit
  2. Higgs-Strahlung
  3. Weak Boson Fusion
  4. Bottom Quark Annihilation
  5. Bibliography

1. Gluon fusion

Gluon fusion is the dominant production channel for ↳Higgs bosons both at the ↳Tevatron and the ↳LHC. This is true not only in the ↳Standard Model, but also in more exotic scenarios like the ↳Minimal Supersymmetric Standard Model. The coupling of the ↳gluons to the Higgs boson is mediated by a top triangle, so that the ↳Feynman diagram to lowest order is given by the left diagram in the following figure:

Gluon Fusion Gluon Fusion (mt->infty)

Lowest order contribution to gg->H in full ↳QCD (left) and in the effective theory (right).

On July 4, 2012, a particle consistent with a Higgs boson of mass 125 GeV was observed at the LHC (see also here and here). For this mass, the Higgs-gluon interaction is well represented by an effective Lagrangian for the limit mt → infinity (mt is the top quark mass). Using this effective interaction, the lowest order contribution is the tree level diagram on the right hand side of the above figure.

1a. QCD corrections

First order QCD corrections to the total rate gg->H have been calculated 1991 by A. Djouadi et al. [Phys.Lett.B264 (1991) 440] and by S. Dawson [Nucl.Phys.B359 (1991) 283]. They turned out to be very large, namely about 70-100%, depending on the Higgs boson mass. This largeness of the first order terms was the main motivation to evaluate the second order corrections.

The first step towards the full NNLO terms was the evaluation of the virtual two-loop corrections [1], for which a sample of diagrams is shown here:

Two-loop diagrams contributing to the process gg->H.

In order to arrive at the full NNLO prediction, one needs to evaluate the real radiation processes as well, i.e., emission of one gluon or quark at one-loop level, and double emission of gluons or quarks at tree level.

Diagrams for single and double real emission.

The main obstacle in performing the full NNLO calculation turns out to be the phase space integration of the double real emission contribution. A similar calculation had been performed only once up to now, namely the classic NNLO Drell-Yan calculation by R. Hamberg, W.L. van Neerven, T. Matsuura [Nucl.Phys.B359 (1991) 343].

After a number of preliminary results [1][2][CFG], the full calculation has been performed by W. Kilgore and myself [3], and independently by two other groups [AM][RSN]. Comparison of this result with the first measurement of the new particle at the LHC provided the first quantitative hint that this particle is indeed the Higgs boson.

1b. Production of a pseudo-scalar Higgs boson

Extended models of particle physics predict a larger variety of Higgs bosons. They differ from one another not only by their mass, but also charge or parity. In the minimal supersymmetric extension of the Standard Model (↳MSSM), for example, there are five Higgs bosons: h and H are electrically neutral and CP-even, A is CP-odd (often called the pseudo-scalar Higgs boson), and H+/- are charged. While the production rate for a light neutral Higgs boson h can be easily estimated from the production cross section of a Standard Model Higgs boson (at least in a certain range of the MSSM parameter space), the couplings of a pseudo-scalar Higgs differ significantly from the case of a CP-even Higgs. The production rate for a pseudo-scalar Higgs boson can nevertheless be computed using the same methods as in the scalar case. This was done independently by two groups: again by W. Kilgore and myself [4], and by Anastasiou and Melnikov [AM]. Another confirmation of these results (including the scalar Higgs production) was obtained by Ravindran et al. [RSN].

1c. Higgs production in Supersymmetry

With M. Steinhauser and F. Hofmann, we have evaluated an effective Lagrangian for Higgs production in minimal ↳Supersymmetry [7], [9], [10]. Once established, the calculation of the gluon fusion process is exactly the same as in the Standard Model, and the results can be taken over from the papers discussed above.

With F. Hofmann and H. Mantler, we have presented the first prediction for the Higgs production cross section in the MSSM, taking into account quark and squark effects both from the top and the bottom sector [17].

These results, and others from [DSV] have recently been implemented in our general code SusHi [23].

1d. Beyond the heavy-top limit

It had been a long-standing issue whether the effective theory approach mentioned above is really valid also at NNLO. With K. Ozeren [13], [14], we calculated terms that are formally suppressed by 1/mt, where mt is the top quark mass. For the gluon-gluon subchannel, this expansion was matched to the high-energy limit obtained from [MBDFV]. (Similar results were obtained in [PRS][PRS]). With K. Ozeren, H. Mantler and S. Marzani [15], we extended the analyses of [14] to all subchannels and found that the heavy-top limit is indeed an excellent approximation (better than 1% accuracy) also at NNLO.

While the above results were all obtained for the fully inclusive cross section, we also studied differential distributions [20] and found similar results. These results give confidence in the heavy top limit for higher order calculations.

2. Higgs-Strahlung

The radiation of a Higgs boson off an electro-weak gauge boson, or "Higgs-Strahlung", was the dominant production process at the Tevatron in the low Higgs mass range; it is also a central process at the LHC though. We provided the first next-to-next-to-leading order prediction which reduces the perturbative uncertainty significantly with respect to lower orders [6]. At higher orders, Higgs-Strahlung receives contributions where the Higgs is radiated off a closed top quark loop. We calculated these terms in Ref. [18].

The gluon-induced terms, though numerically subdominant, introduce a large theoretical uncertainty. By calculation higher orders for this process [22], we managed to gain better theoretical control over this process.

3. Weak Boson Fusion

Text under construction. See Ref. [12].

4. Bottom Quark Annihilation

Text under construction. See Refs. [5] and [16], as well as the program bbh@nnlo.

For other results, please see the following list of publications.

5. Literature:

Journal articles:
[30] E. Bagnaschi, R.V. Harlander, H. Mantler, A. Vicini, M. Wiesemann,
Resummation ambiguities in the Higgs transverse-momentum spectrum in the Standard Model and beyond
WUB/15-06 [arXiv:1510.08850]
JHEP 01 (2016) 090

[29] R.V. Harlander, A. Kulesza, V. Theeuwes, T. Zirke
Soft gluon resummation for gluon-induced Higgs Strahlung
WUB/14-10 [arXiv:1410.0217]
JHEP 11 (2014) 082

[28] R.V. Harlander, H. Mantler, M. Wiesemann
Transverse momentum resummation for Higgs production via gluon fusion in the MSSM
WUB/14-07 [arXiv:1409.0531]
JHEP 11 (2014) 116

[27] R.V. Harlander, A. Tripathi, M. Wiesemann
Higgs production in bottom quark annihilation: Transverse momentum distribution at NNLO+NNLO
WUB/14-02 [arXiv:1403.7196]
Phys. Rev. D 90 (2014) 015017

[26] E. Bagnaschi, R.V. Harlander, S. Liebler, H. Mantler, P. Slavich, A. Vicini
Towards precise predictions for Higgs-boson production in the MSSM
WUB/14-01 [arXiv:1404.0327]
JHEP 06 (2014) 167

[25] R.V. Harlander, T. Neumann
Probing the nature of the Higgs-gluon coupling
WUB/13-08 [arXiv:1308.2225]
Phys. Rev. D 88 (2013) 074015

[24] R.V. Harlander, S. Liebler, T. Zirke
Higgs Strahlung at the Large Hadron Collider in the 2-Higgs-Doublet Model
WUB/13-12 [arXiv:1307.8122]
JHEP 02 (2014) 023

[23] R.V. Harlander, S. Liebler, H. Mantler
SusHi: A program for the calculation of Higgs production in gluon fusion and bottom-quark annihilation in the Standard Model and the MSSM
WUB/12-28 [arXiv:1212.3249]
Comp. Phys. Commun. 184 (2013) 1605-1617

[22] L. Altenkamp, S. Dittmaier, R.V. Harlander, H. Rzehak, T.J.E. Zirke
Gluon-induced Higgs-strahlung at next-to-leading order QCD
WUB/12-21 [arXiv:1211.5015]
JHEP 02 (2013) 078

[21] O. Brein, R.V. Harlander, T.J.E. Zirke
vh@nnlo — Higgs Strahlung at hadron colliders
WUB/12-20 [arXiv:1210.5347]
Comp. Phys. Commun. 184 (2013) 998-1003

[20] R.V. Harlander, T. Neumann, K.J. Ozeren, M. Wiesemann
Top-mass effects in differential Higgs production through gluon fusion at order alpha_s^4
JHEP 08 (2012) 139 [arXiv:1206.0157]

[19] R. Harlander, M. Wiesemann
Jet-veto in bottom-quark induced Higgs production at next-to-next-to-leading order
JHEP 04 (2012) 066 [arXiv:1111.2182]

[18] O. Brein, R. Harlander, M. Wiesemann, T. Zirke
Top-quark mediated effects in hadronic Higgs-Strahlung
Eur. Phys. J. C 72 (2012) 1868 [arXiv:1111.0761]

[17] R.V. Harlander, F. Hofmann, H. Mantler
Supersymmetric Higgs production in gluon fusion
JHEP 02 (2011) 055 [arXiv:1012.3361]
additional material available at this URL

[16] R.V. Harlander, K.J. Ozeren, M. Wiesemann
Higgs plus jet production in bottom quark annihilation at next-to-leading order
Phys. Lett. B 693 (2010) 269 [arXiv:1007.5411]

[15] R.V. Harlander, H. Mantler, S. Marzani, K.J. Ozeren
Higgs production in gluon fusion at next-to-next-to-leading order QCD for finite top mass
Eur. Phys. J. C 66 (2010) 359 [arXiv:0912.2104]

[14] R.V. Harlander and K.J. Ozeren
Finite top mass effects in Higgs production at next-to-next-to-leading order
JHEP 11 (2009) 088 [arXiv:0909.3420]

[13] R.V. Harlander and K.J. Ozeren
Top mass effects in Higgs production at next-to-next-to-leading order QCD: virtual corrections
Phys. Lett. B 679 (2009) 467-472 [arXiv:0907.2997]

[12] R. Harlander, J. Vollinga, M. Weber
Gluon-Induced Weak Boson Fusion
Phys. Rev. C 77 (2008) 053010 [arXiv:0801.3355]

[11] R. Harlander and P. Kant
Higgs production and decay: Analytic results at next-to-leading order QCD
JHEP 0512 (2005) 015 [hep-ph/0509189]

[10] R.V. Harlander and F. Hofmann
Pseudo-scalar Higgs production at next-to-leading order SUSY-QCD
JHEP 0603 (2006) 050 [hep-ph/0507041]

[9] R.V. Harlander and M. Steinhauser
Supersymmetric Higgs production in gluon fusion at next-to-leading order
JHEP 0409 (2004) 066 [hep-ph/0409010]

[8] R.V. Harlander and M. Steinhauser
Effects of SUSY-QCD in hadronic Higgs production at next-to-next-to-leading order
Phys. Rev. D 68 (2003) 111701 [hep-ph/0308210]

[7] R.V. Harlander and M. Steinhauser
Hadronic Higgs Production and Decay in Supersymmetry at Next-to-Leading Order
Phys. Lett. B 574 (2003) 258-268 [hep-ph/0307346]

[6] O. Brein, A. Djouadi, R. Harlander
NNLO QCD corrections to the Higgs-strahlung processes at hadron colliders
Phys. Lett. B 579 (2004) 149 [hep-ph/0307206]

[5] R.V. Harlander and W.B. Kilgore
Higgs boson production in bottom quark fusion at next-to-next-to-leading order
Phys. Rev. D 68 (2003) 013001 [hep-ph/0304035]

[4] R.V. Harlander and W.B. Kilgore
Production of a pseudo-scalar Higgs boson at hadron colliders at next-to-next-to leading order
JHEP 0210 (2002) 017 [hep-ph/0208096]

[3] R.V. Harlander and W.B. Kilgore
Next-to-next-to-leading order Higgs production at hadron colliders
Phys. Rev. Lett. 88 (2002) 201801 [hep-ph/0201206]

[2] R.V. Harlander and W.B. Kilgore
Soft and virtual corrections to pp→H+X at NNLO
Phys. Rev. D 64 (2001) 01301 [hep-ph/0102241]

[1] R.V. Harlander
Virtual corrections to gg→H to two loops in the heavy top limit
Phys. Lett. B 492 (2000) 74 [hep-ph/0007289]

Proceedings contributions and other publications:
[P16] R.V. Harlander, A. Tripathi, M. Wiesemann
Resummed Higgs pT distribution at NNLO+NNLL in bottom-quark annihilation
WUB/14-06 [arXiv:1407.3184]

[P15] R. Harlander, M. Mühlleitner, J. Rathsman, M. Spira, O. Stål
Recommendations for the evaluation of Higgs production cross sections and branching ratios at the LHC in the Two-Higgs-Doublet Model
WUB/13-19 [arXiv:1312.5571]
(part of LHC-HXSWG – not submitted for publication)

[P14] R.V. Harlander
Higgs production in bottom quark annihilation and gluon fusion
WUB/12-24; contributed to Loops&Legs 2012
PoS (LL2012) 040

[P13] R. Harlander, M. Krämer, M. Schumacher
Bottom-quark associated Higgs-boson production: reconciling the four- and five-flavour scheme approach
available from this URL [arXiv:1112.3478]
CERN-PH-TH/2011-134, FR-PHENO-2011-009, TTK-11-17, WUB/11-04

[P12] R. Harlander, H. Mantler, S. Marzani, K.J. Ozeren
Higgs production in gluon fusion at NNLO for finite top quark mass
PoS (RADCOR2009) 049 [arXiv:1001.2971]

[P11] R.V. Harlander,
Higgs production at the Large Hadron Collider: theoretical status
J. Phys. G 35 (2008) 033001

[P10] R. Harlander
Standard and SUSY Higgs production at the LHC
Pramana 67 (2006) 875-884 [hep-ph/0606095]
Proceedings of WHEPP9, Bhubaneswar, India, Jan 3-14, 2006

[P9] R. Harlander
Precise predictions for Higgs cross sections at the Large Hadron Collider
Loops and Legs in Quantum Field Theory, Zinnowitz, Germany, April 25-30, 2004,
Nucl. Phys. B 135C (2004) 30-34

[P8] O. Brein, M. Ciccolini, S. Dittmaier, A. Djouadi, R. Harlander, M. Krämer
Precision calculations for associated WH and ZH production at hadron colliders
Physics at TeV Colliders, Les Houches, France, May 26-Jun 6, 2003 [hep-ph/0402003]

[P7] R. Harlander
Supersymmetric Higgs production at the Large Hadron Collider
HEP2003 Europhysics Conference (EPS 2003), Aachen, Germany, July 17-23, 2003
Eur. Phys. J. C
33 (2004) S454 [hep-ph/0311005]

[P6] R.V. Harlander and W.B. Kilgore
Techniques for NNLO Higgs production in the standard model and the MSSM
XXXVIIIth Rencontres de Moriond, Les Arcs, France, 22-29 March 2003 [hep-ph/0305204]

[P5] R. Harlander
Recent Theoretical Progress on Higgs Production at Hadron Colliders,
HCP2002, Karlsruhe, Germany, 29 Sep-4 Oct 2002

[P4] R.Harlander and W.Kilgore
Scalar and pseudo-scalar Higgs production at hadron colliders
RADCOR / Loops and Legs 2002, Kloster Banz, Germany, 8-13 Sep 2002 [hep-ph/0211380]

[P3] W.B. Kilgore and R.V. Harlander
Inclusive Higgs boson production at hadron colliders at next-to-next-to-leading order
37th Rencontres de Moriond on QCD and Hadronic Interactions, Les Arcs, France, 16-23 Mar 2002 [hep-ph/0205152]

[P2] R.V. Harlander and W.B. Kilgore
Inclusive Higgs production at next-to-next-to-leading order
Snowmass 2001, Colorado, 30 Jun-21 Jul 2001 [hep-ph/0110200]

[P1] R. Harlander and W. Kilgore
Higgs production in gluon fusion to O(alpha_s^4)
DPF 2000, Columbus, Ohio, 9-12 Aug 2000
Int. J. Mod. Phys. A 16S1A (2001) 305 [hep-ph/0012176]

Robert Harlander: Research -/- Home -/- TTP Karlsruhe -/- CERN Theory -/- HET Brookhaven
last updated on 1 Aug 2013 by RH