mt2

library1.3.1pypypi✓ verified 83d ago

mt2 provides a fast, numerically stable computation of the stransverse mass (M_T2) as a NumPy universal function (ufunc). It is commonly used in high-energy physics for SUSY searches and dilepton event analysis. Current version: 1.3.1, with release cadence approximately every 3-4 months. Requires Python >=3.9.

data

pip install mt2

github ↗package ↗

INSTALL

IMPORT

SIG · MT2

mt2

datapythonv1.3.1

Install

3.7s avg

Import

257ms

Disk

91MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v1.3.1 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 0.254s · 93.3MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 3.7s · import 0.260s · 86MB

91MB installed

● package 91MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

mt2

✓ import mt2

No submodule or deprecated import path exists. Direct import works.

Compute the stransverse mass for a single event.

import numpy as np import mt2 # Define transverse momenta and masses pa = np.array([100.0, 50.0, 0.0]) # (px, py, m) for visible particle a pb = np.array([80.0, -30.0, 0.0]) # (px, py, m) for visible particle b pt_miss = np.array([20.0, 10.0]) # missing transverse momentum (px, py) m_invis = 0.0 # mass of the invisible particle # Compute M_T2 result = mt2.mt2(pa, pb, pt_miss, m_invis) print(f"M_T2 = {result:.2f}")

Debug

Known issues

breakingIn v1.2.1, numpy 2.0 compatibility was fixed. Older versions (pre-1.2.1) may fail with numpy 2.0.

fix

Upgrade to mt2>=1.2.1 and ensure numpy is compatible (numpy>=1.23,<2.1 recommended).

affects: <1.2.1

breakingIn v1.2.2, the Python source code was moved to src/mt2 to avoid import confusion. Direct imports from the old location (e.g., import mt2 as before) still work, but any references to internal modules may break.

fix

Use standard `import mt2`. If you relied on internal paths, adjust imports accordingly.

affects: >=1.2.2

deprecatedIn v1.2.0, the function signature changed: the argument order was updated for consistency. Old code using positional arguments may break.

fix

Use keyword arguments or check the new signature: mt2(pa, pb, pt_miss, m_invis, ...).

affects: >=1.2.0

gotchaThe `pt_miss` vector must have exactly 2 elements (px, py). Providing a 3-element vector (e.g., (px, py, m)) will cause an error.

fix

Ensure pt_miss is a 1D array of length 2. Use e.g. np.array([px, py]).

affects: all

gotchaNegative masses in input are clipped to zero in v1.3.0 and later. In earlier versions, negative masses might produce undefined results or errors.

fix

Upgrade to >=1.3.0 or explicitly clip negative masses to zero before passing to mt2.

affects: <1.3.0

Errors

Common errors & fixes

ModuleNotFoundError: No module named 'mt2'

The package is not installed or installed in an incorrect environment.

fix

Run `pip install mt2` or `conda install -c conda-forge mt2`.

ImportError: numpy.core.multiarray failed to import

A version mismatch between numpy and mt2 (e.g., numpy 2.0.0 with mt2 <1.2.1).

fix

Upgrade mt2 to >=1.2.1 and ensure numpy is compatible: `pip install 'mt2>=1.2.1'`.

ValueError: operands could not be broadcast together with shapes

Input arrays have incompatible shapes. mt2 expects either scalar or 1D arrays of same length or broadcastable shapes.

fix

Reshape inputs to have consistent leading dimensions, ensuring pa, pb, pt_miss are all 1D arrays of same length or broadcastable.

AssertionError: Invalid input dimensions

pa or pb must have exactly 3 elements (px, py, m) and pt_miss exactly 2 elements (px, py). This error arises from wrong shape.

fix

Check shapes: pa.shape == (3,), pb.shape == (3,), pt_miss.shape == (2,). For arrays, ensure last dimension is correct.

Upgrade

Version history

1.3.1latest on PyPI · released Oct 9, 2025

Audit

Dependencies

numpyrequiredCore dependency for ufunc and array operations.

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/tpgillam/mt2 ↗

packagehttps://pypi.org/project/mt2/ ↗