# Measuring the mass, width, and couplings of semi-invisible resonances with the matrix element method

## Abstract

We demonstrate the use of the matrix element method (MEM) for the measurement of masses, widths, and couplings in the case of single or pair production of semi-invisibly decaying resonances. For definiteness, we consider the two-body decay of a generic resonance to a visible particle from the Standard Model (SM) and a massive invisible particle. It is well known that the mass difference can be extracted from the endpoint of a transverse kinematic variable like the transverse mass, ${M}_{T}$, or the Cambridge ${M}_{T2}$ variable, but measuring the overall mass scale is a very difficult problem. We show that the MEM can be used to obtain not only the absolute mass scale, but also the width of the resonance and the tensor structure of its couplings. Apart from new physics searches, our results can be readily applied to the case of SM $W$ boson production at the CERN Large Hadron Collider (LHC), where one can repeat the measurements of the $W$ properties in a general and model-independent framework.

- Authors:

- Publication Date:

- Research Org.:
- Univ. of Hawaii, Honolulu, HI (United States); Univ. of Florida, Gainesville, FL (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE Office of Science (SC), High Energy Physics (HEP)

- OSTI Identifier:
- 1525560

- Alternate Identifier(s):
- OSTI ID: 1598600

- Grant/Contract Number:
- SC0010504; SC0010296

- Resource Type:
- Published Article

- Journal Name:
- Physical Review D

- Additional Journal Information:
- Journal Name: Physical Review D Journal Volume: 99 Journal Issue: 11; Journal ID: ISSN 2470-0010

- Publisher:
- American Physical Society (APS)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

### Citation Formats

```
Betancur, Amalia, Debnath, Dipsikha, Gainer, James S., Matchev, Konstantin T., and Shyamsundar, Prasanth. Measuring the mass, width, and couplings of semi-invisible resonances with the matrix element method. United States: N. p., 2019.
Web. https://doi.org/10.1103/PhysRevD.99.116007.
```

```
Betancur, Amalia, Debnath, Dipsikha, Gainer, James S., Matchev, Konstantin T., & Shyamsundar, Prasanth. Measuring the mass, width, and couplings of semi-invisible resonances with the matrix element method. United States. https://doi.org/10.1103/PhysRevD.99.116007
```

```
Betancur, Amalia, Debnath, Dipsikha, Gainer, James S., Matchev, Konstantin T., and Shyamsundar, Prasanth. Tue .
"Measuring the mass, width, and couplings of semi-invisible resonances with the matrix element method". United States. https://doi.org/10.1103/PhysRevD.99.116007.
```

```
@article{osti_1525560,
```

title = {Measuring the mass, width, and couplings of semi-invisible resonances with the matrix element method},

author = {Betancur, Amalia and Debnath, Dipsikha and Gainer, James S. and Matchev, Konstantin T. and Shyamsundar, Prasanth},

abstractNote = {We demonstrate the use of the matrix element method (MEM) for the measurement of masses, widths, and couplings in the case of single or pair production of semi-invisibly decaying resonances. For definiteness, we consider the two-body decay of a generic resonance to a visible particle from the Standard Model (SM) and a massive invisible particle. It is well known that the mass difference can be extracted from the endpoint of a transverse kinematic variable like the transverse mass, MT, or the Cambridge MT2 variable, but measuring the overall mass scale is a very difficult problem. We show that the MEM can be used to obtain not only the absolute mass scale, but also the width of the resonance and the tensor structure of its couplings. Apart from new physics searches, our results can be readily applied to the case of SM W boson production at the CERN Large Hadron Collider (LHC), where one can repeat the measurements of the W properties in a general and model-independent framework.},

doi = {10.1103/PhysRevD.99.116007},

journal = {Physical Review D},

number = 11,

volume = 99,

place = {United States},

year = {2019},

month = {6}

}

https://doi.org/10.1103/PhysRevD.99.116007

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